Skull Base Chordomas and Chondrosarcomas — MCQs

10 questions

What is the most common structural location within the bone for conventional chondrosarcoma?

All of the following statements about synovial sarcoma are true, except -

A 68-year-old man has many months history of progressive hearing loss, unsteady gait, tinnitus, and facial pain. An MRI scan reveals a tumor at the cerebellopontine angle. Which of the following cranial nerves is this tumor most likely to affect?

Which brain tumor is the most radiosensitive?

A 14 year old male presents with mushroom like tumor in the distal femur for past 2 years. Which of the following features suggest malignant transformation?

Which of the following is an epiphyseal tumor?

Nasopharyngeal chordoma arises from:-

Chordoma arises from:

A lady comes to OPD after fall from scooty. Her vitals are stable. She is having continuous, clear watery discharge from nose after 2 days. This is most likely a feature of?

Q10

FISCH classification is used for-

Skull Base Chordomas and Chondrosarcomas Indian Medical PG Practice Questions and MCQs

Question 1: What is the most common structural location within the bone for conventional chondrosarcoma?

A. Intramedullary (Correct Answer)
B. Juxtacortical
C. Epiphyseal
D. Periosteal

Explanation: ***Intramedullary*** - This is the **most common location** for conventional chondrosarcoma, accounting for approximately **75-85%** of cases [1]. - These tumors arise within the **medullary cavity** (central or intramedullary location) and grow expansively within the bone [1]. - They typically show lytic destruction with internal ring-and-arc or popcorn calcifications on imaging. - Conventional chondrosarcoma is synonymous with central or intramedullary chondrosarcoma [1]. *Periosteal* - Periosteal (surface) chondrosarcoma is a **rare subtype** accounting for only **1-2%** of chondrosarcomas. - These arise from the periosteum on the bone surface, not within the medullary cavity. - They have a better prognosis compared to conventional (intramedullary) chondrosarcoma. *Juxtacortical* - This refers to tumors arising at or near the **bone surface** (cortical region) [1]. - Peripheral/juxtacortical chondrosarcoma accounts for approximately **10-15%** of cases and is much less common than the central type. - Secondary chondrosarcoma arising from osteochondroma is an example of peripheral chondrosarcoma [1]. *Epiphyseal* - Chondrosarcoma **rarely arises in the epiphysis** of long bones. - Conventional chondrosarcoma typically involves the **metaphysis and diaphysis**, with predilection for flat bones (pelvis, ribs) and long bones (femur, humerus) [2]. - Epiphyseal location would be highly unusual for this tumor. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1202-1204. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Osteoarticular And Connective Tissue Disease, pp. 673-674.

Question 2: All of the following statements about synovial sarcoma are true, except -

A. Usually seen in patients less than 50 years of age
B. Occur more often at extraarticular sites
C. Originate from synovial lining (Correct Answer)
D. Knee and foot are common sites involved

Explanation: ***Originate from synovial lining*** - This statement is **false**. While named "synovial sarcoma" due to its histological resemblance to synovium, it **does not originate from synovial cells** [1]. - Its origin is believed to be from **primitive mesenchymal cells** that can differentiate along various cell lines, not directly from the synovial lining of joints. *Usually seen in patients less than 50 years of age* - This statement is **true**. Synovial sarcoma predominantly affects **adolescents and young adults**, with a median age of diagnosis typically in the 3rd or 4th decade of life [1]. - It is one of the more common soft tissue sarcomas in this younger age group. *Occur more often at extraarticular sites* - This statement is **true**. Despite its name, synovial sarcoma most frequently occurs in **extra-articular locations**, often near large joints but not within the joint capsule itself [1]. - Common sites include the deep soft tissues of the extremities, especially the **thigh and knee**, and less often the trunk or head and neck. *Knee and foot are common sites involved* - This statement is **true**. The **knee** (particularly the thigh region around the knee) and **foot/ankle** are indeed among the most frequent locations for synovial sarcoma [1]. - These tumors often present as a deep-seated mass in these areas. **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1225-1226.

Question 3: A 68-year-old man has many months history of progressive hearing loss, unsteady gait, tinnitus, and facial pain. An MRI scan reveals a tumor at the cerebellopontine angle. Which of the following cranial nerves is this tumor most likely to affect?

A. sixth cranial nerve
B. eighth cranial nerve (Correct Answer)
C. tenth cranial nerve
D. fourth cranial nerve

Explanation: ***eighth cranial nerve*** - The **eighth cranial nerve (vestibulocochlear nerve)** is located in the **cerebellopontine angle** and is responsible for **hearing and balance**. [1], [2] - Symptoms like **progressive hearing loss, tinnitus, and unsteady gait (vertigo)** are classic signs of compression or damage to this nerve, often caused by an **acoustic neuroma (vestibular schwannoma)** in this region. [2], [3] - **CN VIII is the FIRST and MOST COMMONLY affected nerve** in cerebellopontine angle tumors, making it the correct answer. - The **facial pain** mentioned suggests compression of the **trigeminal nerve (CN V)** by a large tumor, which can occur as the tumor expands, but CN VIII remains the primary nerve affected. *sixth cranial nerve* - The **sixth cranial nerve (abducens nerve)** innervates the **lateral rectus muscle**, responsible for **abduction of the eye**. - Damage would typically result in **diplopia** and an inability to move the eye laterally, which is not described. - This nerve is **rarely affected** by CPA tumors due to its anatomical location. *tenth cranial nerve* - The **tenth cranial nerve (vagus nerve)** controls **pharyngeal and laryngeal muscles**, as well as **parasympathetic innervation to many organs**. - Damage would typically cause **dysphagia**, **hoarseness**, or autonomic dysfunction, none of which are presented. - The vagus nerve is **not typically affected** by CPA tumors. *fourth cranial nerve* - The **fourth cranial nerve (trochlear nerve)** innervates the **superior oblique muscle**, aiding in **eye movement**. - Damage would primarily lead to **vertical diplopia**, particularly when looking down and in, which is not mentioned as a symptom. - This nerve is **not affected** by CPA tumors due to its location.

Question 4: Which brain tumor is the most radiosensitive?

A. Glioblastoma multiforme
B. Astrocytoma
C. Ependymoma
D. Medulloblastoma (Correct Answer)

Explanation: ***Medulloblastoma*** - **Medulloblastoma** is highly **radiosensitive** due to its rapid cell proliferation and immature cellular characteristics, making radiation therapy a cornerstone of treatment. - This tumor commonly originates in the **cerebellum** and is one of the most common malignant brain tumors in children. *Ependymoma* - **Ependymomas** are generally only moderately **radiosensitive**; while radiation is used, it is often delivered in higher doses directly to the tumor bed. - These tumors arise from **ependymal cells** lining the ventricles and spinal cord. *Glioblastoma multiforme* - **Glioblastoma multiforme (GBM)** is known for its marked **radioresistance**, requiring high doses of radiation often in combination with chemotherapy, and still having a poor prognosis. - It is the most aggressive and common type of primary **brain tumor in adults**, characterized by rapid growth and extensive infiltration. *Astrocytoma* - The **radiosensitivity** of astrocytomas varies significantly by grade; **low-grade astrocytomas** are relatively radioresistant, while **anaplastic astrocytomas** have intermediate radiosensitivity. - These tumors originate from **astrocytes**, a type of glial cell, and can occur in various parts of the brain and spinal cord.

Question 5: A 14 year old male presents with mushroom like tumor in the distal femur for past 2 years. Which of the following features suggest malignant transformation?

A. Cartilage thickness $>2 \mathrm{~cm}$ (Correct Answer)
B. Presence of cartilage cap
C. Location in metaphysis
D. Size less than 1 cm

Explanation: ***Cartilage thickness >2 cm*** - A **cartilage cap thickness greater than 2 cm** in an osteochondroma in an adult (or >3 cm in children) is a strong indicator of **malignant transformation** into a secondary peripheral **chondrosarcoma**. [2], [3] - **Key imaging finding:** Cartilage cap measured on MRI or CT scan - Other features suggesting malignant transformation include continued growth after skeletal maturity, new or increasing pain, cortical destruction, and new soft tissue mass. [2], [3] *Presence of cartilage cap* - All osteochondromas have a cartilage cap by definition - this is a normal feature, not a sign of malignancy. [1] - The **thickness** of the cap, not its presence, is what matters. *Location in metaphysis* - Osteochondromas typically arise from the metaphysis near the growth plate - this is a normal location. [3] - Location alone does not indicate malignant transformation. *Size less than 1 cm* - Small size suggests a benign, stable lesion. - Malignant transformation is suggested by **increasing size** and growth after skeletal maturity, not small size. [2] **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, p. 1202. [2] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Common Clinical Problems From Osteoarticular And Connective Tissue Disease, pp. 672-673. [3] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. Bones, Joints, and Soft Tissue Tumors, pp. 1202-1204.

Question 6: Which of the following is an epiphyseal tumor?

A. Osteosarcoma
B. Osteoid osteoma
C. Chondroblastoma (Correct Answer)
D. Adamantinoma

Explanation: ***Chondroblastoma*** - **Chondroblastoma** is a rare, benign cartilaginous tumor that typically originates in the **epiphysis** of long bones before the closure of growth plates. - It is histologically characterized by chondroblast-like cells, multinucleated giant cells, and chondroid matrix, and radiographically appears as a lytic lesion with a sclerotic rim in the epiphysis. *Osteosarcoma* - **Osteosarcoma** is the most common primary malignant bone tumor and typically originates in the **metaphysis** of long bones, particularly around the knee. - It invades the surrounding bone and soft tissues, often presenting with a **Codman triangle** or **sunburst pattern** on imaging studies. *Osteoid osteoma* - **Osteoid osteoma** is a benign bone-forming tumor primarily found in the **cortex** of long bones, although it can occur in other locations, presenting with nocturnal pain relieved by NSAIDs. - It is characterized by a central radiolucent nidus surrounded by reactive sclerotic bone. *Adamantinoma* - **Adamantinoma** is an extremely rare, low-grade malignant tumor that almost exclusively occurs in the **tibia diaphysis**. - It is thought to originate from epithelial cells and presents as a lytic lesion within the cortical bone, often with a polycystic appearance.

Question 7: Nasopharyngeal chordoma arises from:-

A. Luschka's bursa
B. Pharyngeal bursa
C. Rathke's pouch
D. Notochord (Correct Answer)

Explanation: Correct Option: Notochord - **Chordomas** are rare malignant tumors that arise from embryonic remnants of the **notochord** [1] - The notochord is a flexible rod-like structure that forms the primitive axial skeleton during embryonic development - Chordomas typically occur along the **midline** at sites where notochordal remnants persist, most commonly at the **skull base (clivus/nasopharynx)** and **sacrococcygeal region** [1] Incorrect Option: Luschka's bursa - **Luschka's bursa** (also known as the pharyngeal bursa) is a small indentation or pocket in the nasopharynx posterior to the pharyngeal tonsil - While located in the nasopharynx, it is a **normal anatomical structure**, not an embryological remnant that gives rise to tumors - Not associated with chordoma development Incorrect Option: Pharyngeal bursa - **Pharyngeal bursa** is another term for **Luschka's bursa** (they are synonymous) - It is a normal anatomical structure in the nasopharynx - Not related to the embryonic remnants that give rise to chordomas Incorrect Option: Rathke's pouch - **Rathke's pouch** is an embryonic invagination of the stomodeum (primitive oral cavity) that gives rise to the **anterior pituitary gland** - Tumors arising from remnants of Rathke's pouch are **craniopharyngiomas**, which are distinct from chordomas - Craniopharyngiomas are typically suprasellar, while chordomas are more commonly found at the clivus or sacrum

Question 8: Chordoma arises from:

A. Pharyngeal bursa
B. Notochord (Correct Answer)
C. Rathke’s pouch
D. Luschka's bursa

Explanation: ***Notochord*** - Chordoma is a **rare, slow-growing malignant bone tumor** that originates from **persistent notochordal remnants**. - The notochord is a flexible rod-like structure that serves as the primary axial support during embryonic development, eventually becoming the **nucleus pulposus** of the intervertebral discs. *Pharyngeal bursa* - The pharyngeal bursa is a normal anatomical variant, a small recess in the **posterior wall of the nasopharynx**. - It is not associated with the development of chordomas. *Rathke's pouch* - Rathke's pouch is an **ectodermal invagination** from the roof of the primitive mouth (stomodeum) that gives rise to the **anterior pituitary gland**. - Tumors arising from remnants of Rathke's pouch are typically **craniopharyngiomas**, not chordomas. *Luschka's bursa* - This term is sometimes used to refer to a **pharyngeal bursa**, as mentioned in the first incorrect option. - It is not the origin of chordomas.

Question 9: A lady comes to OPD after fall from scooty. Her vitals are stable. She is having continuous, clear watery discharge from nose after 2 days. This is most likely a feature of?

A. CSF rhinorrhoea (Correct Answer)
B. Acute respiratory infection
C. Rhinitis
D. Middle cranial fossa fracture

Explanation: ***CSF rhinorrhoea*** - **Clear watery discharge** appearing **two days after head trauma** (fall from scooty) is highly suggestive of **cerebrospinal fluid (CSF) rhinorrhoea**. - This occurs due to a breach in the **skull base**, allowing CSF to leak from the subarachnoid space into the nasal cavity. *Acute respiratory infection* - An acute respiratory infection typically presents with symptoms like **fever, cough**, and **nasal discharge** that is often thicker and discolored, not clear and watery. - The onset of discharge two days after trauma without other signs of infection also makes this less likely. *Rhinitis* - Rhinitis involves inflammation of the nasal mucosa, leading to watery discharge, sneezing, and congestion. - However, the traumatic etiology and the specific timing of the discharge make **CSF leak** a more pertinent diagnosis than simple rhinitis. *Middle cranial fossa fracture* - While a **middle cranial fossa fracture** can cause CSF leakage, the discharge from the nose (rhinorrhoea) typically originates from an **anterior cranial fossa fracture**. - A middle cranial fossa fracture is more commonly associated with **otorrhoea** (CSF leakage from the ear) if the temporal bone is involved.

Question 10: FISCH classification is used for-

A. Juvenile nasopharyngeal angiofibroma
B. Nasopharyngeal carcinoma
C. Vestibular schwannoma
D. Glomus tumor (Correct Answer)

Explanation: ***Glomus tumor*** - The **FISCH classification** is a surgical staging system used to classify **glomus tumors** based on their extent and involvement of surrounding structures. - This classification helps guide surgical management and predict procedural outcomes for these highly vascular tumors. *Juvenile nasopharyngeal angiofibroma* - **Radkowski's classification**, or **Andrews' classification**, are commonly used for staging **juvenile nasopharyngeal angiofibroma**, not FISCH. - These classifications categorize tumors based on their extension into the nasal cavity, paranasal sinuses, orbit, or intracranial space. *Nasopharyngeal ca* - The staging of **nasopharyngeal carcinoma** is typically based on the **AJCC (American Joint Committee on Cancer) TNM classification system**. - This system assesses the **tumor (T)** size and local extension, **node (N)** involvement, and **metastasis (M)**. *Vestibular schwannoma* - **Vestibular schwannomas** are usually staged using systems that describe their size and extension into the **cerebellopontine angle** and brainstem, such as the **Koos grade**. - The FISCH classification is specifically for **glomus tumors** of the temporal bone and is not applicable to vestibular schwannomas.

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