Dermatopathology US Medical PG Practice Questions and MCQs
Practice US Medical PG questions for Dermatopathology. These multiple choice questions (MCQs) cover important concepts and help you prepare for your exams.
Dermatopathology US Medical PG Question 1: A 52-year-old woman presents with erosions in her mouth that are persistent and painful. She says that symptoms appeared gradually 1 week ago and have progressively worsened. She also notes that, several days ago, flaccid blisters appeared on her skin, which almost immediately transformed to erosions as well. Which of the following is the most likely diagnosis?
- A. Molluscum contagiosum
- B. Psoriasis
- C. Pemphigus vulgaris (Correct Answer)
- D. Bullous pemphigoid
- E. Staphylococcal infection (scalded skin syndrome)
Dermatopathology Explanation: **Pemphigus vulgaris**
- The presence of **persistent and painful oral erosions** followed by **flaccid blisters** that quickly break into erosions on the skin is highly characteristic of pemphigus vulgaris. This is due to **acantholysis** (loss of cell-to-cell adhesion) within the epidermis.
- The oral lesions typically precede skin lesions and are often the first symptom, as seen in this patient, and are very painful.
*Molluscum contagiosum*
- Causes **dome-shaped, umbilicated papules** and does not present with widespread flaccid blisters or painful erosions.
- It is a viral infection common in children and immunocompromised individuals.
*Psoriasis*
- Characterized by **erythematous plaques with silvery scales**, typically found on extensor surfaces.
- It does not involve flaccid blisters or widespread mucosal erosions.
*Bullous pemphigoid*
- Presents with **tense bullae** on an erythematous or urticarial base, which are less likely to rupture quickly compared to the flaccid blisters of pemphigus vulgaris. Oral lesions are less common (affecting 10-30%) and generally less severe than in pemphigus vulgaris.
- It involves autoantibodies against **hemidesmosomes**, leading to subepidermal blistering.
*Staphylococcal infection (scalded skin syndrome)*
- Primarily affects infants and young children, causing widespread **erythema and superficial blistering**, resembling a burn, leading to epidermal sloughing.
- It can cause diffuse nonscarring exfoliation and not well-demarcated oral erosions or flaccid blisters leading to erosions in this age group as is seen in this patient.
Dermatopathology US Medical PG Question 2: A 52-year-old Caucasian man presents to the clinic for evaluation of a mole on his back that he finds concerning. He states that his wife noticed the lesion and believes that it has been getting larger. On inspection, the lesion is 10 mm in diameter with irregular borders. A biopsy is performed. Pathology reveals abnormal melanocytes forming nests at the dermo-epidermal junction and discohesive cell growth into the epidermis. What is the most likely diagnosis?
- A. Desmoplastic melanoma
- B. Lentigo maligna melanoma
- C. Superficial spreading melanoma (Correct Answer)
- D. Nodular melanoma
- E. Acral lentiginous melanoma
Dermatopathology Explanation: ***Superficial spreading melanoma***
- This is the **most common type of melanoma**, accounting for 70% of cases, and typically presents with a **radial growth phase** showing irregular borders and enlarging size.
- Histopathology revealing **nests of abnormal melanocytes at the dermo-epidermal junction** and **discohesive cell growth into the epidermis** (pagetoid spread) is characteristic of superficial spreading melanoma.
*Desmoplastic melanoma*
- Characterized by **fibrous stroma** and often **neural invasion**, with a less pigmented appearance, which is not described.
- Typically presents as a firm, often amelanotic nodule, and can be more aggressive.
*Lentigo maligna melanoma*
- Primarily found in **chronically sun-damaged areas** of the elderly, often on the face, and begins as a flat, tan-brown macule that slowly enlarges.
- Histologically, it shows **atypical melanocytes along the basal layer** of a thinned epidermis, not necessarily forming nests or extensive discohesive growth into the epidermis early on.
*Nodular melanoma*
- This type of melanoma has a **vertical growth phase from the outset**, appearing as a rapidly growing, dark, elevated lesion without a significant preceding radial growth phase.
- Histologically, it involves a substantial dermal component with **minimal or absent intraepidermal radial growth**.
*Acral lentiginous melanoma*
- Occurs on the **palms, soles, or under the nails (subungual)**, and is less associated with sun exposure, often presenting as a dark, spreading lesion.
- Its histological features involve **lentiginous proliferation of atypical melanocytes** along the dermo-epidermal junction with spread into the rete ridges in an acral distribution.
Dermatopathology US Medical PG Question 3: A 47-year-old woman comes to her primary care doctor because of a new, pruritic rash. She was gardening in her yard two days ago and now has an eczematous papulovesicular rash on both ankles. You also note a single, 5 mm brown lesion with a slightly raised border on her left thigh. You prescribe a topical corticosteroid for contact dermatitis. Which of the following is the appropriate next step for the thigh lesion?
- A. Further questioning (Correct Answer)
- B. Full thickness biopsy
- C. Simple shave biopsy
- D. Reassurance
- E. Topical corticosteroid
Dermatopathology Explanation: ***Further questioning***
- **Obtaining a thorough history** about the brown lesion is crucial to assess for features suspicious for melanoma or other skin cancers (**A**symmetry, **B**order irregularity, **C**olor variation, **D**iameter >6mm, **E**volving).
- This step helps determine the urgency and type of subsequent diagnostic procedures, such as whether a biopsy is immediately needed and if so, what kind.
*Full thickness biopsy*
- A full-thickness biopsy, also known as an **excisional biopsy**, is generally reserved for lesions highly suspicious for melanoma where complete removal and accurate staging are desired.
- Performing an invasive procedure without first gathering more information about the lesion's history and characteristics is premature.
*Simple shave biopsy*
- A shave biopsy samples only the superficial layers of the skin and is appropriate for lesions that are primarily epidermal and raised, such as **seborrheic keratoses** or **basal cell carcinomas** not suspected of deep invasion.
- It is generally **contraindicated for pigmented lesions suspicious for melanoma**, as it may interfere with accurate staging if the lesion is malignant.
*Reassurance*
- Reassurance is inappropriate given the description of a **new, pigmented lesion with a slightly raised border**, which could indicate a potential malignancy.
- All suspicious skin lesions warrant further investigation to rule out serious conditions.
*Topical corticosteroid*
- Topical corticosteroids are used to treat inflammatory skin conditions like eczema or contact dermatitis, which is the diagnosis for the patient's ankle rash.
- Applying a corticosteroid to a **pigmented lesion of unknown etiology** is incorrect and potentially harmful, as it would not address a neoplastic process and could mask symptoms.
Dermatopathology US Medical PG Question 4: A 34-year-old man presents to his dermatologist with white scaly papules and plaques on his extensor arms, elbows, knees, and shins. Scaly and flaky eruptions are also present on his ears, eyebrows, and scalp. He describes the lesions as being itchy and irritating. When the scales are scraped away, pinpoint bleeding is noted. His vital signs are unremarkable, and physical examination is otherwise within normal limits. Which of the following is the best initial test for this patient’s condition?
- A. No tests are necessary (Correct Answer)
- B. Serum autoantibodies
- C. Plain film X-rays of the hands and feet
- D. Skin biopsy
- E. Wood’s lamp
Dermatopathology Explanation: **No tests are necessary**
- The patient's presentation with **white scaly papules and plaques** on extensor surfaces (elbows, knees, shins), along with involvement of the ears, eyebrows, and scalp, are classic signs of **psoriasis**.
- The phenomenon of **pinpoint bleeding** upon scraping the scales (Auspitz sign) is highly distinctive for psoriasis, making additional diagnostic tests initially unnecessary.
*Serum autoantibodies*
- This test is typically used to diagnose **autoimmune connective tissue diseases** like lupus or rheumatoid arthritis, which have different clinical presentations.
- Psoriasis is a T-cell mediated autoimmune disease, but specific serum autoantibodies are not used for its primary diagnosis.
*Plain film X-rays of the hands and feet*
- X-rays are used to assess **joint damage** in conditions like psoriatic arthritis, which is a complication of psoriasis.
- However, the patient's current presentation describes only skin lesions, so joint imaging is not the best initial diagnostic step.
*Skin biopsy*
- While a **skin biopsy** can confirm psoriasis, the clinical picture here is so characteristic that a biopsy is generally reserved for **atypical presentations** or when the diagnosis is uncertain.
- It is not the *best initial test* when the diagnosis is clear clinically.
*Wood’s lamp*
- A **Wood's lamp** (UV light) is primarily used to detect **fungal infections** (e.g., tinea) or pigmentation disorders.
- It does not aid in the diagnosis of psoriasis, which has a distinct morphology visible to the naked eye.
Dermatopathology US Medical PG Question 5: An investigator studying the molecular characteristics of various malignant cell lines collects tissue samples from several families with a known mutation in the TP53 tumor suppressor gene. Immunohistochemical testing performed on one of the cell samples stains positive for desmin. This sample was most likely obtained from which of the following neoplasms?
- A. Squamous cell carcinoma
- B. Rhabdomyosarcoma (Correct Answer)
- C. Prostate cancer
- D. Endometrial carcinoma
- E. Melanoma
Dermatopathology Explanation: ***Rhabdomyosarcoma***
- **Desmin** is an intermediate filament present in **muscle cells**, and its positive staining is a definitive marker for tumors of muscle origin
- A **rhabdomyosarcoma** is a malignant tumor of **skeletal muscle** differentiation, thus explaining the positive desmin staining.
*Squamous cell carcinoma*
- **Squamous cell carcinomas** are epithelial tumors that typically stain positive for **cytokeratin**, not desmin, as they originate from epithelial cells.
- They are characterized by features such as **intercellular bridges** and **keratinization**.
*Prostate cancer*
- **Prostate cancer** is an adenocarcinoma, meaning it's derived from glandular epithelial cells, and would stain positive for markers like **PSA (prostate-specific antigen)**, not desmin.
- This tumor type is characterized by glandular differentiation.
*Endometrial carcinoma*
- **Endometrial carcinomas** are adenocarcinomas of the uterine lining, derived from glandular epithelial cells, and would express **cytokeratins**, not desmin.
- Histologically, they show glandular structures and atypical endometrial cells.
*Melanoma*
- **Melanomas** are malignant tumors of melanocytes and would stain positive for markers such as **S-100**, **HMB-45**, and **Mart-1**, not desmin.
- These tumors originate from neural crest cells and are not muscle-derived.
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