A 25-year-old man presents with a mass on his neck. He says that he first noticed the mass a few weeks ago while taking a shower. Since then, the mass has not increased in size. He denies any pain or difficulty in swallowing. Past medical history is unremarkable. Family history is significant for his father who had his thyroid removed when he was around his age but doesn’t know why. Review of systems is significant for occasional episodes of anxiety that include a pounding headache, racing heart, and sweating. His vital signs include: pulse 88/min, blood pressure 133/87 mm Hg, temperature 37.2°C (99.0°F), and respiratory rate 14/min. He is 183 cm (6 ft 2 in) tall with long extremities. On physical examination, the patient appears cachectic. There is a palpable 4 cm x 4 cm nodule present on the left lobe of the thyroid. Which of the following is the most likely thyroid pathology in this patient?
Q2
A 35-year-old man comes to the physician for evaluation of a neck mass and hoarseness. He has no history of major medical illness. Physical examination shows a 2.5-cm fixed, irregular thyroid nodule. His serum calcitonin concentration is elevated. The nodule is most likely comprised of cells that are embryologically derived from which of the following structures?
Q3
A 44-year-old woman comes to the physician for the evaluation of a 1-month history of fatigue and difficulty swallowing. During this period, she has also had dry skin, thinning hair, and rounding of her face. She has type 1 diabetes mellitus and rheumatoid arthritis. Her father had a thyroidectomy for papillary thyroid cancer. The patient had smoked one pack of cigarettes daily for 20 years but quit 3 years ago. She drinks 2–3 glasses of wine daily. Her current medications include insulin, omeprazole, and daily ibuprofen. She appears well. Her temperature is 36.3°C (97.3°F), pulse is 62/min, and blood pressure is 102/76 mm Hg. Examination of the neck shows a painless, diffusely enlarged thyroid gland. Cardiopulmonary examination shows no abnormalities. Further evaluation is most likely to show which of the following?
Q4
A 36-year-old woman presents with thyroid swelling. She has been healthy until now and follows all the healthcare precautions except for missing a flu shot this year. On physical examination, the thyroid gland is diffusely enlarged and tender to palpation. Laboratory findings show a decreased serum TSH level and elevated erythrocyte sedimentation rate. Which of the following histopathologic findings would most likely be found in the thyroid gland of this patient?
Q5
A 55-year-old woman comes to the physician because of a 4-month history of a painless lump on her neck. Examination shows a hard nodule on the left side of her neck. A fine-needle aspiration biopsy shows well-differentiated cuboidal cells arranged spherically around colloid. She undergoes thyroidectomy. Histopathological examination of the surgical specimen shows invasion of the thyroid capsule and blood vessels. Which of the following cellular events is most likely involved in the pathogenesis of this patient's condition?
Q6
A 40-year-old woman comes to the physician because of a 3-month history of a lump on her neck. The lump is mildly painful. She appears healthy. Examination shows a swelling on the left side of her neck that moves on swallowing. Cardiopulmonary examination shows no abnormalities. Her TSH is 3.6 μU/mL. Ultrasound shows a 4.0-cm (1.6-in) hypoechoic mass in the left thyroid lobe. Fine-needle aspiration of the mass shows neoplastic follicular cells. Molecular analysis of the aspirate shows a mutation in the RAS gene. Which of the following is the most appropriate next step in management?
Q7
A 16-year-old male presents to the emergency department complaining of episodes of pounding headache, chest fluttering, and excessive sweating. He has a past history of kidney stones that are composed of calcium oxalate. He does not smoke or drink alcohol. Family history reveals that his mother died of thyroid cancer. Vital signs reveal a temperature of 37.1°C (98.7°F), blood pressure of 200/110 mm Hg and pulse of 120/min. His 24-hour urine calcium, serum metanephrines, and serum normetanephrines levels are all elevated. Mutation of which of the following genes is responsible for this patient's condition?
Q8
A 47-year-old woman comes to the physician because of a 2-month history of a lump on her neck and a 1-week history of hoarseness. Examination shows a 3-cm, firm, non-tender nodule on the anterior neck. Further evaluation confirms a thyroid malignancy, and she undergoes thyroidectomy. Histopathologic examination of the surgical specimen shows lymphatic invasion. Genetic analysis shows an activating mutation in the RET/PTC genes. Microscopic examination of the surgical specimen is most likely to also show which of the following?
Q9
A 21-year-old male college student is very anxious about having thyroid cancer as he found a lump in his neck a few days ago. He has also had diarrhea and a feeling of warmth on his face for 3 days now. His father and uncle both have been diagnosed with thyroid cancer. The lump is about 1 cm in diameter and is fixed and nontender on palpation. Physical examination is otherwise unremarkable. Ultrasound shows a non-cystic cold nodule that requires fine needle aspiration for diagnosis. Thyroid functions tests are normal, and his calcitonin level is 346 ug/ml. Which of the following genetic mutations would warrant thyroidectomy in this patient?
Q10
A 24-year-old man comes to the physician because of 2 episodes of bleeding from the rectum over the past month. The patient’s father died of colon cancer at the age of 42. The patient has no history of any serious illness and takes no medications. He does not smoke. His vital signs are within normal limits. Physical examination shows a small hard mass over the right mandible that is nontender and fixed to the underlying bone. A similarly hard and painless 5 × 5 mass is palpated over the rectus abdominis muscle. On examination of the rectum, a polypoid mass is palpated at fingertip. Proctosigmoidoscopy shows numerous polyps. Which of the following best explains these findings?
Thyroid neoplasms US Medical PG Practice Questions and MCQs
Question 1: A 25-year-old man presents with a mass on his neck. He says that he first noticed the mass a few weeks ago while taking a shower. Since then, the mass has not increased in size. He denies any pain or difficulty in swallowing. Past medical history is unremarkable. Family history is significant for his father who had his thyroid removed when he was around his age but doesn’t know why. Review of systems is significant for occasional episodes of anxiety that include a pounding headache, racing heart, and sweating. His vital signs include: pulse 88/min, blood pressure 133/87 mm Hg, temperature 37.2°C (99.0°F), and respiratory rate 14/min. He is 183 cm (6 ft 2 in) tall with long extremities. On physical examination, the patient appears cachectic. There is a palpable 4 cm x 4 cm nodule present on the left lobe of the thyroid. Which of the following is the most likely thyroid pathology in this patient?
A. Follicular adenoma
B. Medullary carcinoma (Correct Answer)
C. Giant cell thyroiditis
D. Papillary carcinoma
E. Anaplastic carcinoma
Explanation: ***Medullary carcinoma***
- This patient's presentation with a **neck mass**, family history of thyroid removal at a young age, and episodic symptoms of **pounding headache, racing heart, and sweating** (suggestive of **pheochromocytoma**) strongly points to medullary thyroid carcinoma (MTC) as part of **Multiple Endocrine Neoplasia type 2B (MEN 2B)**.
- The **tall stature, long extremities, and cachectic appearance** (Marfanoid habitus) are characteristic features of **MEN 2B syndrome**, which consists of MTC, pheochromocytoma, Marfanoid habitus, and mucosal neuromas.
- MTC arises from **parafollicular C cells** and secretes **calcitonin**; it is associated with **RET proto-oncogene mutations** in hereditary cases.
*Follicular adenoma*
- While follicular adenomas can present as a **solitary thyroid nodule**, they are **benign** and do not present with the systemic symptoms (anxiety-like episodes, palpitations, headaches) or family history suggestive of a hereditary cancer syndrome.
- There is no association with **pheochromocytoma** or **Marfanoid habitus**.
*Giant cell thyroiditis*
- **Giant cell thyroiditis (subacute thyroiditis/De Quervain thyroiditis)** is characterized by a **painful, tender thyroid** nodule, often preceded by a viral upper respiratory infection.
- The patient's nodule is described as **non-painful**, and his symptoms do not align with the typical course of thyroiditis (fever, elevated ESR, transient hyperthyroidism).
*Papillary carcinoma*
- **Papillary thyroid carcinoma** is the most common type of thyroid cancer and typically presents as a **painless thyroid nodule**.
- However, it is **not associated** with a strong family history of early-onset thyroid disease, episodic symptoms suggesting **pheochromocytoma**, or **Marfanoid habitus**, unlike medullary carcinoma in MEN 2B.
*Anaplastic carcinoma*
- **Anaplastic thyroid carcinoma** is a highly aggressive cancer, usually presenting in **older individuals (>60 years old)** with a **rapidly enlarging, painful neck mass** and symptoms of local **compression** (dyspnea, dysphagia, hoarseness).
- The patient's **young age** (25 years) and the **non-aggressive nature** of the mass (stable size over weeks) make anaplastic carcinoma highly unlikely.
Question 2: A 35-year-old man comes to the physician for evaluation of a neck mass and hoarseness. He has no history of major medical illness. Physical examination shows a 2.5-cm fixed, irregular thyroid nodule. His serum calcitonin concentration is elevated. The nodule is most likely comprised of cells that are embryologically derived from which of the following structures?
A. Second branchial pouch
B. Fourth branchial arch
C. Surface ectoderm
D. Third branchial pouch
E. Neural crest cells (Correct Answer)
Explanation: ***Neural crest cells***
- The elevated **serum calcitonin** in the presence of a thyroid nodule is highly suggestive of **medullary thyroid carcinoma (MTC)**.
- **MTC** originates from the **parafollicular C cells** of the thyroid, which are embryologically derived from **neural crest cells** that migrate to the **ultimobranchial body** (from the 4th/5th pharyngeal pouch) during development and subsequently integrate into the thyroid gland.
- This is the definitive embryological origin of calcitonin-producing C cells.
*Second branchial pouch*
- The second branchial pouch typically gives rise to the **palatine tonsil crypts** and **tonsillar fossa**.
- It is not associated with the development of the **parafollicular C cells** or thyroid malignancies.
*Fourth branchial arch*
- The fourth branchial arch gives rise to the **superior laryngeal nerve** and associated laryngeal cartilages.
- While the **ultimobranchial body** (from the 4th/5th pharyngeal pouch) does contribute C cells to the thyroid, these cells themselves are derived from **neural crest cells** that migrate to this structure, not from the pouch itself.
- Therefore, the embryological origin is neural crest, not the branchial arch/pouch.
*Surface ectoderm*
- Surface ectoderm forms structures such as the **epidermis of the skin**, **hair**, **nails**, and **lens of the eye**.
- It does not contribute to the development of the **C cells** or the thyroid gland.
*Third branchial pouch*
- The third branchial pouch gives rise to the **inferior parathyroid glands** and the majority of the **thymus**.
- While it contributes to endocrine tissues, it does not form the **parafollicular C cells** of the thyroid.
Question 3: A 44-year-old woman comes to the physician for the evaluation of a 1-month history of fatigue and difficulty swallowing. During this period, she has also had dry skin, thinning hair, and rounding of her face. She has type 1 diabetes mellitus and rheumatoid arthritis. Her father had a thyroidectomy for papillary thyroid cancer. The patient had smoked one pack of cigarettes daily for 20 years but quit 3 years ago. She drinks 2–3 glasses of wine daily. Her current medications include insulin, omeprazole, and daily ibuprofen. She appears well. Her temperature is 36.3°C (97.3°F), pulse is 62/min, and blood pressure is 102/76 mm Hg. Examination of the neck shows a painless, diffusely enlarged thyroid gland. Cardiopulmonary examination shows no abnormalities. Further evaluation is most likely to show which of the following?
A. Positive thyroid peroxidase antibodies and thyroglobulin antibodies in serum (Correct Answer)
B. Diffusely increased uptake on a radioactive iodine scan
C. Increased uptake on radioactive iodine scan in discrete 1-cm area
D. Large irregular nuclei, nuclear grooves, and Psammoma bodies on thyroid biopsy
E. Positive immunohistochemical stain for calcitonin on thyroid biopsy
Explanation: ***Positive thyroid peroxidase antibodies and thyroglobulin antibodies in serum***
- The patient's symptoms (fatigue, dry skin, thinning hair, rounded face, bradycardia) are classic for **hypothyroidism**.
- The presence of **Type 1 diabetes mellitus** and **rheumatoid arthritis** suggests an underlying autoimmune diathesis, making **Hashimoto thyroiditis** (autoimmune hypothyroidism) highly likely, which is characterized by positive thyroid peroxidase (TPO) and thyroglobulin antibodies.
*Diffusely increased uptake on a radioactive iodine scan*
- **Diffusely increased uptake** on a radioactive iodine scan is characteristic of **hyperthyroidism**, such as in **Graves' disease**, which contradicts the patient's hypothyroid symptoms.
- In Hashimoto thyroiditis, especially in the hypothyroid phase, uptake is typically **reduced or normal**, not diffusely increased.
*Increased uptake on radioactive iodine scan in discrete 1-cm area*
- **Increased uptake in a discrete area** (a 'hot nodule') suggests a **toxic adenoma** or a multinodular goiter, which are causes of hyperthyroidism, not hypothyroidism.
- This finding would also contradict the patient's clinical presentation of hypothyroidism.
*Large irregular nuclei, nuclear grooves, and Psammoma bodies on thyroid biopsy*
- These are classic cytologic features seen in **papillary thyroid carcinoma**, not Hashimoto thyroiditis.
- While the patient's father had papillary thyroid cancer, her clinical presentation is strongly indicative of hypothyroidism, and her diffusely enlarged, painless gland is more consistent with Hashimoto's than a focal malignant lesion showing these specific cytological features.
*Positive immunohistochemical stain for calcitonin on thyroid biopsy*
- A positive immunohistochemical stain for **calcitonin** is diagnostic for **medullary thyroid carcinoma**.
- This is a neuroendocrine tumor and does not typically present with the generalized hypothyroid symptoms described in the patient.
Question 4: A 36-year-old woman presents with thyroid swelling. She has been healthy until now and follows all the healthcare precautions except for missing a flu shot this year. On physical examination, the thyroid gland is diffusely enlarged and tender to palpation. Laboratory findings show a decreased serum TSH level and elevated erythrocyte sedimentation rate. Which of the following histopathologic findings would most likely be found in the thyroid gland of this patient?
A. Extensive fibrosis of the stroma
B. Mixed cellular infiltration with multinuclear giant cells (Correct Answer)
C. Lymphocytic infiltration with germinal centers
D. Orphan Annie nuclei with psammoma bodies
E. Sheets of polygonal cells in amyloid stroma
Explanation: ***Mixed cellular infiltration with multinuclear giant cells***
- The patient's symptoms of a **diffusely enlarged and tender thyroid**, suppressed **TSH**, elevated **ESR**, and a recent viral illness (missing flu shot) are classic for **subacute granulomatous (De Quervain's) thyroiditis**.
- Histopathologically, this condition is characterized by a **disruptive inflammatory infiltrate** with **multinucleated giant cells** engulfing colloid, surrounded by granulomatous inflammation.
*Extensive fibrosis of the stroma*
- This finding is characteristic of **Riedel's thyroiditis**, a rare form of chronic thyroiditis.
- Riedel's thyroiditis typically presents as a **hard, fixed, and painless goiter**, often leading to compressive symptoms, which does not match this patient's tender goiter.
*Lymphocytic infiltration with germinal centers*
- This pattern is typical of **Hashimoto's thyroiditis**, an **autoimmune thyroid disease**.
- Hashimoto's usually presents with a **painless goiter** and often leads to **hypothyroidism**, not the tender, hyperthyroid-like state seen here.
*Orphan Annie nuclei with psammoma bodies*
- These are hallmark features associated with **papillary thyroid carcinoma**.
- This patient's acute presentation with **tenderness, inflammation**, and temporary hyperthyroidism is inconsistent with a malignant thyroid neoplasm.
*Sheets of polygonal cells in amyloid stroma*
- This describes the histopathology of **medullary thyroid carcinoma**.
- Medullary thyroid carcinoma arises from parafollicular C-cells and is characterized by the production of **calcitonin** and often has a genetic predisposition, which is not suggested by the patient's presentation.
Question 5: A 55-year-old woman comes to the physician because of a 4-month history of a painless lump on her neck. Examination shows a hard nodule on the left side of her neck. A fine-needle aspiration biopsy shows well-differentiated cuboidal cells arranged spherically around colloid. She undergoes thyroidectomy. Histopathological examination of the surgical specimen shows invasion of the thyroid capsule and blood vessels. Which of the following cellular events is most likely involved in the pathogenesis of this patient's condition?
A. TSH receptor gene mutation
B. Activation mutation in the BRAF gene
C. Mutation in the RET proto-oncogene
D. p53 tumor suppressor gene inactivation
E. PAX8-PPAR gamma gene rearrangement (Correct Answer)
Explanation: ***PAX8-PPAR gamma gene rearrangement***
- The description of a **painless neck lump**, **well-differentiated cuboidal cells arranged spherically around colloid**, and **invasion of the thyroid capsule and blood vessels** is highly classic for **follicular thyroid carcinoma**.
- **PAX8-PPAR gamma rearrangement** is a characteristic genetic alteration found in a significant subset of **follicular thyroid carcinomas** and sometimes in follicular adenomas, playing a crucial role in tumorigenesis.
*TSH receptor gene mutation*
- This mutation is associated with **toxic thyroid adenomas** (Plummer's disease) and **diffuse toxic goiter** (Graves' disease), leading to hyperthyroidism.
- While it can cause nodular growth, it typically results in a **hyperfunctioning nodule** and is not primarily linked to the invasive features of follicular carcinoma described.
*Activation mutation in the BRAF gene*
- **BRAF V600E mutation** is the most common genetic alteration found in **papillary thyroid carcinoma**, which typically presents with **papillary architecture**, nuclear features like **Orphan Annie eye nuclei**, and **psammoma bodies**.
- The histological description of "well-differentiated cuboidal cells arranged spherically around colloid" does not fit papillary carcinoma.
*Mutation in the RET proto-oncogene*
- **RET proto-oncogene mutations** are characteristic of **medullary thyroid carcinoma**, a neuroendocrine tumor arising from parafollicular C cells.
- Medullary thyroid carcinoma has distinct histological features (e.g., amyloid deposition) and clinical presentations (e.g., calcitonin secretion) that are not described in this case.
*p53 tumor suppressor gene inactivation*
- **p53 inactivation** is primarily associated with **anaplastic thyroid carcinoma** and **poorly differentiated thyroid carcinoma**.
- These are highly aggressive tumors that would present with rapid growth, significant invasion, and poorly differentiated or anaplastic histology, which contradicts the "well-differentiated" description in the patient's biopsy.
Question 6: A 40-year-old woman comes to the physician because of a 3-month history of a lump on her neck. The lump is mildly painful. She appears healthy. Examination shows a swelling on the left side of her neck that moves on swallowing. Cardiopulmonary examination shows no abnormalities. Her TSH is 3.6 μU/mL. Ultrasound shows a 4.0-cm (1.6-in) hypoechoic mass in the left thyroid lobe. Fine-needle aspiration of the mass shows neoplastic follicular cells. Molecular analysis of the aspirate shows a mutation in the RAS gene. Which of the following is the most appropriate next step in management?
A. Radioiodine therapy
B. External beam radiation
C. Total thyroidectomy
D. Thyroid lobectomy (Correct Answer)
E. Watchful waiting
Explanation: ***Thyroid lobectomy***
- A **thyroid lobectomy** is appropriate for a **solitary thyroid nodule** with suspicious features (hypoechoic, neoplastic follicular cells, **RAS mutation**) and a size of 4.0 cm, as it allows for pathological diagnosis and treatment while preserving the other lobe.
- The **RAS mutation** indicates a moderate risk of malignancy, and for a unilateral tumor of this size, lobectomy is often preferred over total thyroidectomy as it minimizes the risk of **hypoparathyroidism** and the need for lifelong thyroid hormone replacement.
*Radioiodine therapy*
- This therapy is primarily used as an **adjunctive treatment** after surgical removal of thyroid cancer, especially for **metastatic disease** or **large residual tumors**, not as a primary treatment for a localized tumor before surgery.
- It is also typically reserved for **differentiated thyroid cancers** (papillary, follicular) that have demonstrated uptake, and surgical removal is the initial step for diagnosis and treatment.
*External beam radiation*
- **External beam radiation** is generally reserved for **advanced, inoperable thyroid cancers** or for cases with **extracapsular invasion** or **distant metastases** that are not amenable to radioiodine therapy.
- It carries significant side effects and is not a first-line treatment for an early-stage, localized thyroid nodule.
*Total thyroidectomy*
- **Total thyroidectomy** is indicated for larger thyroid cancers (>4 cm), bilateral disease, or aggressive histological subtypes.
- Given the patient's **unilateral tumor** with a **RAS mutation** (which signifies moderate risk), a thyroid lobectomy is appropriate as the initial surgical approach, with total thyroidectomy reserved if final pathology shows aggressive features.
*Watchful waiting*
- **Watchful waiting** is inappropriate given the presence of **neoplastic follicular cells** and a **RAS mutation**, as these findings indicate a significant risk of malignancy.
- The nodule size of 4.0 cm and molecular findings warrant surgical intervention for definitive diagnosis and treatment rather than observation.
Question 7: A 16-year-old male presents to the emergency department complaining of episodes of pounding headache, chest fluttering, and excessive sweating. He has a past history of kidney stones that are composed of calcium oxalate. He does not smoke or drink alcohol. Family history reveals that his mother died of thyroid cancer. Vital signs reveal a temperature of 37.1°C (98.7°F), blood pressure of 200/110 mm Hg and pulse of 120/min. His 24-hour urine calcium, serum metanephrines, and serum normetanephrines levels are all elevated. Mutation of which of the following genes is responsible for this patient's condition?
A. RET proto-oncogene (Correct Answer)
B. BCL2
C. BRAF
D. BCR-ABL
E. HER-2/neu (C-erbB2)
Explanation: ***RET proto-oncogene***
- The patient's symptoms (pounding headache, chest fluttering, sweating, hypertension, tachycardia), elevated metanephrines, and a history of kidney stones (suggesting **hyperparathyroidism**) combined with a family history of **thyroid cancer** are classic for **Multiple Endocrine Neoplasia type 2A (MEN2A)**.
- **MEN2A** is caused by a germline mutation in the **RET proto-oncogene** and typically involves **medullary thyroid carcinoma**, **pheochromocytoma** (explaining the adrenal symptoms), and **primary hyperparathyroidism**.
*BCL2*
- The **BCL2 gene** is an **anti-apoptotic gene** primarily associated with lymphomas, particularly **follicular lymphoma**, where its overexpression promotes cell survival.
- Mutations or translocations involving BCL2 are not linked to endocrine disorders like MEN2A or the specific combination of symptoms seen in this patient.
*BRAF*
- The **BRAF gene** encodes a protein involved in cell growth signaling and is commonly mutated in various cancers, most notably **melanoma** and **papillary thyroid carcinoma**.
- While associated with thyroid cancer, a BRAF mutation does not explain the pheochromocytoma, hyperparathyroidism, or the specific family history indicative of MEN2A.
*BCR-ABL*
- The **BCR-ABL fusion gene** results from the **Philadelphia chromosome translocation (t(9;22))** and is the hallmark of **chronic myeloid leukemia (CML)** and some cases of acute lymphoblastic leukemia.
- This gene is a potent oncogene in hematopoietic malignancies and has no association with the endocrine tumors or symptoms described in the patient.
*HER-2/neu (C-erbB2)*
- **HER-2/neu (C-erbB2)** is an oncogene that encodes a receptor tyrosine kinase and is primarily associated with **breast cancer** and some **gastric cancers**, where its overexpression indicates a more aggressive tumor and guides targeted therapy.
- This gene is not implicated in the pathogenesis of MEN2A or the constellation of symptoms observed in this patient.
Question 8: A 47-year-old woman comes to the physician because of a 2-month history of a lump on her neck and a 1-week history of hoarseness. Examination shows a 3-cm, firm, non-tender nodule on the anterior neck. Further evaluation confirms a thyroid malignancy, and she undergoes thyroidectomy. Histopathologic examination of the surgical specimen shows lymphatic invasion. Genetic analysis shows an activating mutation in the RET/PTC genes. Microscopic examination of the surgical specimen is most likely to also show which of the following?
A. Pleomorphic giant cells with numerous atypical mitotic figures
B. Cuboidal cells arranged spherically around colloid lakes
C. Hyperplastic epithelium with colloid scalloping
D. Calcified spherules and large oval cells with empty-appearing nuclei (Correct Answer)
E. Sheets of polygonal cells surrounding amyloid deposition
Explanation: ***Calcified spherules and large oval cells with empty-appearing nuclei***
- The presence of an **activating mutation in RET/PTC genes**, **lymphatic invasion**, and a new neck lump with hoarseness (suggesting nerve involvement) are highly characteristic of **papillary thyroid carcinoma**.
- Microscopic features of papillary thyroid carcinoma include **Psammoma bodies (calcified spherules)**, **Orphan Annie eye nuclei (large oval cells with empty-appearing nuclei)**, and nuclear grooves.
*Pleomorphic giant cells with numerous atypical mitotic figures*
- This description typically refers to **anaplastic thyroid carcinoma**, a highly aggressive and undifferentiated tumor.
- While anaplastic carcinoma can present with rapid growth and hoarseness, it is less commonly associated with a **RET/PTC mutation** (BRAF mutations are more common) and typically has a much poorer prognosis, often presenting with a rapidly enlarging mass rather than a 2-month history suggestive of a more indolent tumor.
*Cuboidal cells arranged spherically around colloid lakes*
- This morphology is characteristic of **follicular thyroid carcinoma** or **follicular adenoma**.
- While follicular tumors can have RET/PTC mutations in some variants, the classic features described (empty-appearing nuclei and psammoma bodies) are absent here.
*Hyperplastic epithelium with colloid scalloping*
- This describes the histologic features seen in **Graves' disease** or **diffuse toxic goiter**, a benign condition.
- It is not indicative of malignancy, and the patient's presentation with a solitary nodule and hoarseness points to a malignant process.
*Sheets of polygonal cells surrounding amyloid deposition*
- This is the classic microscopic appearance of **medullary thyroid carcinoma**.
- Medullary thyroid carcinoma is also associated with **RET mutations**, but these are typically **germline or somatic RET point mutations** (e.g., RET M918T), not RET/PTC rearrangements, and it arises from parafollicular C cells, producing calcitonin, not thyroid hormones.
Question 9: A 21-year-old male college student is very anxious about having thyroid cancer as he found a lump in his neck a few days ago. He has also had diarrhea and a feeling of warmth on his face for 3 days now. His father and uncle both have been diagnosed with thyroid cancer. The lump is about 1 cm in diameter and is fixed and nontender on palpation. Physical examination is otherwise unremarkable. Ultrasound shows a non-cystic cold nodule that requires fine needle aspiration for diagnosis. Thyroid functions tests are normal, and his calcitonin level is 346 ug/ml. Which of the following genetic mutations would warrant thyroidectomy in this patient?
A. A loss of function of PPARɣ
B. MEN1 gene mutation
C. Down expression of the Ras protooncogene
D. RET gene mutation (Correct Answer)
E. Activating mutation of the BRAF gene
Explanation: ***RET gene mutation***
- The patient's symptoms (neck lump, flushing, diarrhea, elevated calcitonin, family history of thyroid cancer) are highly suggestive of **medullary thyroid carcinoma (MTC)**. MTC is strongly associated with **activating germline mutations in the RET proto-oncogene**, which warrant prophylactic thyroidectomy.
- An elevated **calcitonin level** is a key biochemical marker for MTC, and a positive family history, especially with features of MEN 2 syndrome, points towards a germline RET mutation.
*A loss of function of PPARɣ*
- **PPARɣ (Peroxisome Proliferator-Activated Receptor gamma)** loss of function is not directly associated with medullary thyroid carcinoma or the symptoms described.
- Mutations in PPARG are occasionally seen in follicular thyroid carcinoma, but not MTC.
*MEN1 gene mutation*
- **MEN1 gene mutations** are associated with **Multiple Endocrine Neoplasia Type 1 (MEN 1)**, which includes parathyroid hyperplasia, pituitary adenomas, and pancreatic endocrine tumors, but generally **not medullary thyroid carcinoma**.
- While MEN1 can cause endocrine tumors, it does not typically present with the significantly elevated calcitonin or the specific type of thyroid cancer seen in this patient.
*Down expression of the Ras protooncogene*
- **RAS gene mutations** (like HRAS, KRAS, NRAS) are commonly found in **follicular and papillary thyroid carcinomas**, but not in medullary thyroid carcinoma.
- "Down expression" or reduced expression of a proto-oncogene would typically reduce its oncogenic potential, which is less likely to cause a rapidly growing, aggressively presenting tumor like MTC.
*Activating mutation of the BRAF gene*
- **BRAF V600E mutation** is the most common genetic alteration in **papillary thyroid carcinoma (PTC)**. BRAF is a serine/threonine kinase involved in the MAPK signaling pathway.
- While PTC is a common thyroid cancer, the patient's presentation with flushing, diarrhea, and high calcitonin is classic for **medullary thyroid carcinoma**, not papillary thyroid carcinoma.
Question 10: A 24-year-old man comes to the physician because of 2 episodes of bleeding from the rectum over the past month. The patient’s father died of colon cancer at the age of 42. The patient has no history of any serious illness and takes no medications. He does not smoke. His vital signs are within normal limits. Physical examination shows a small hard mass over the right mandible that is nontender and fixed to the underlying bone. A similarly hard and painless 5 × 5 mass is palpated over the rectus abdominis muscle. On examination of the rectum, a polypoid mass is palpated at fingertip. Proctosigmoidoscopy shows numerous polyps. Which of the following best explains these findings?
A. Familial polyposis of the colon
B. Peutz-Jeghers syndrome
C. Turcot’s syndrome
D. Gardner’s syndrome (Correct Answer)
E. Lynch’s syndrome
Explanation: ***Gardner's syndrome***
- This syndrome is a variant of **familial adenomatous polyposis (FAP)**, characterized by numerous **colonic polyps** (leading to rectal bleeding) in conjunction with **extra-intestinal manifestations**.
- The extra-intestinal features described, such as **osteomas** (small hard mass over the mandible) and **desmoid tumors** (painless 5 × 5 mass over the rectus abdominis muscle), are classic findings of Gardner's syndrome. The family history of colon cancer further supports this diagnosis.
*Familial polyposis of the colon*
- Familial adenomatous polyposis (FAP) primarily involves the development of **hundreds to thousands of adenomatous colonic polyps**, leading to a high risk of colorectal cancer.
- While it explains the rectal polyps and family history, it does **not account for the extra-intestinal manifestations** like osteomas and desmoid tumors, which are key to Gardner's syndrome.
*Peutz-Jeghers syndrome*
- This syndrome is characterized by **hamartomatous polyps** throughout the gastrointestinal tract and **mucocutaneous hyperpigmentation** (dark spots) on the lips, buccal mucosa, and digits.
- The patient's presentation does not include hamartomatous polyps or mucocutaneous pigmentation.
*Turcot's syndrome*
- Turcot's syndrome is a rare condition involving the co-occurrence of **colorectal polyps** (often adenomatous) and **central nervous system (CNS) tumors**, such as medulloblastoma or glioblastoma.
- The patient presents with osteomas and desmoid tumors, which are not CNS manifestations central to Turcot's syndrome.
*Lynch's syndrome*
- Lynch syndrome (hereditary nonpolyposis colorectal cancer, HNPCC) is characterized by an increased risk of developing **colorectal cancer** and other cancers (e.g., endometrial, ovarian) due to defects in **DNA mismatch repair genes**.
- It typically involves fewer polyps than FAP and does not present with the specific extra-intestinal symptoms like osteomas or desmoid tumors seen in this patient.
Want unlimited practice?
Get full access to all questions, explanations, and performance tracking.
