Dermatopathology Practice Questions

Q: Histological pattern suggests the diagnosis as:

Cylindroma. ***Cylindroma*** - Characterized by **"jigsaw puzzle" pattern** of basaloid cell nests surrounded by thick **eosinophilic hyaline sheaths**. - Shows **basement membrane-like material** separating cell clusters, creating the distinctive cylindrical appearance. *Spindle cell carcinoma* - Composed of **elongated spindle-shaped cells** arranged in fascicles or storiform patterns. - Lacks the characteristic **hyaline sheaths** and basaloid cell nests seen in cylindroma. *Pleomorphic adenoma* - Shows **mixed epithelial and mesenchymal components** with chondromyxoid stroma. - Contains **ductal structures** and **myoepithelial cells** rather than the cylindrical basaloid pattern. *Mucoepidermoid carcinoma* - Characterized by **three cell types**: mucous cells, epidermoid cells, and intermediate cells. - Shows **cystic spaces** filled with mucin, lacking the hyaline cylindrical pattern.

Q: Which cytokeratin is characteristically expressed in Merkel cell carcinoma?

Cytokeratin 20. **Explanation:** Merkel cell carcinoma (MCC) is a highly aggressive, primary neuroendocrine carcinoma of the skin. The diagnosis relies heavily on immunohistochemistry (IHC). **Why Cytokeratin 20 (CK20) is correct:** CK20 is the most characteristic and diagnostic marker for Merkel cell carcinoma. It typically shows a **perinuclear "dot-like" staining pattern**, which is a classic high-yield finding for NEET-PG. While CK20 is also expressed in intestinal epithelium and adenocarcinomas of the GI tract, its presence in a small blue round cell tumor of the skin is highly specific for MCC. **Analysis of Incorrect Options:** * **Cytokeratin 7 (CK7):** This is typically **negative** in MCC. CK7 is more commonly expressed in adenocarcinomas of the lung, breast, and upper GI tract. The CK20+/CK7- profile helps differentiate MCC from metastatic small cell carcinoma of the lung (which is usually CK20-/CK7- or CK7+). * **Cytokeratin 19:** While CK19 can be expressed in various epithelial tumors, it lacks the diagnostic specificity required for MCC. * **Cytokeratin 18:** CK18 is a low-molecular-weight cytokeratin found in most simple epithelia. While MCC may express it, it is not the "characteristic" or defining marker used for diagnosis in a clinical/exam setting. **High-Yield Clinical Pearls for NEET-PG:** * **Origin:** Derived from mechanoreceptor cells (Merkel cells) in the basal layer of the epidermis. * **Etiology:** Strongly associated with the **Merkel Cell Polyomavirus (MCPyV)** in ~80% of cases. * **IHC Profile:** Positive for **CK20 (dot-like)**, Synaptophysin, and Chromogranin A. It is **Negative for TTF-1** (helps rule out metastatic small cell lung cancer). * **Clinical Presentation:** Often follows the **AEIOU** mnemonic: **A**symptomatic, **E**xpanding rapidly, **I**mmune suppressed, **O**lder than 50, **U**V-exposed skin.

Q: What are the characteristic margins of squamous cell carcinoma?

Everted. **Explanation:** The characteristic margin of **Squamous Cell Carcinoma (SCC)** is **everted (turned outward)**. This occurs because the malignant epithelial cells at the edge of the ulcer undergo rapid, uncontrolled proliferation [1]. This excessive growth at the periphery causes the edges to spill over the surrounding normal skin, creating a "heaped-up" or cauliflower-like appearance [2]. **Analysis of Options:** * **Everted (Correct):** Typical of rapidly growing malignant epithelial tumors like SCC [1]. The exuberant growth of neoplastic cells at the margins pushes the edges outward. * **Rolled (Incorrect):** This is the hallmark of **Basal Cell Carcinoma (BCC)**. The margins appear pearly, translucent, and beaded due to the slow, radial spread of tumor nests beneath the epidermis. * **Undermined (Incorrect):** Characteristic of **Tuberculosis (TB) ulcers**. The infection destroys the subcutaneous tissue faster than the overlying skin, leaving the edges hanging over the ulcer base. * **Inverted (Incorrect):** These margins are seen in **Trophic ulcers** (e.g., pressure sores or diabetic ulcers), where there is a lack of healing and the edges punch inward. **High-Yield Clinical Pearls for NEET-PG:** * **SCC Histology:** Look for "Keratin pearls" and "Intercellular bridges" (desmosomes) [1]. * **Precursor Lesions:** Actinic keratosis and Bowen’s disease are common precursors [1]. * **Marjolin’s Ulcer:** A specific type of SCC arising in chronic scars or long-standing burn wounds; it is notoriously aggressive [1]. * **Punch-out edges:** Classically seen in **Syphilitic (gummatous) ulcers**. **References:** [1] Cross SS. Underwood's Pathology: A Clinical Approach. 6th ed. Disorders Involving Inflammatory And Haemopoietic Cells, pp. 643-645. [2] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, p. 1158.

Q: Histological clefts in Lichen planus are described as:

Max-Joseph spaces. **Explanation:** **Lichen Planus (LP)** is a chronic inflammatory dermatosis characterized histologically by a "saw-tooth" appearance of rete ridges and a dense, band-like lymphocytic infiltrate at the dermo-epidermal junction [1]. **Why Max-Joseph Spaces is Correct:** The primary pathology in LP is the immunological destruction of basal keratinocytes (liquefactive degeneration). When this basal cell damage becomes extensive, it leads to a weakening of the dermo-epidermal junction [1]. Small areas of focal separation or "clefts" form between the epidermis and dermis; these histological gaps are known as **Max-Joseph spaces**. **Analysis of Incorrect Options:** * **Civatte bodies:** These are apoptotic, eosinophilic keratinocytes found in the lower epidermis or papillary dermis. While characteristic of LP, they are cellular remnants, not histological clefts. * **Wickham’s striae:** This is a **clinical** finding, not a histological one. It refers to the white, reticulated lines seen on the surface of LP papules, corresponding histologically to focal orthohyperkeratosis and wedge-shaped hypergranulosis. * **Auspitz’s sign:** This is a clinical sign associated with **Psoriasis**, where pinpoint bleeding occurs after the removal of a scale due to thinning of the suprapapillary plate and dilated capillaries. **High-Yield Pearls for NEET-PG:** * **The "6 Ps" of LP:** Planar, Purple, Polygonal, Pruritic, Papules, and Plaques. * **Key Histology:** Hyperkeratosis (without parakeratosis), Wedge-shaped hypergranulosis, Saw-tooth rete ridges, and Band-like infiltrate. * **Koebner Phenomenon:** LP (along with Psoriasis and Vitiligo) shows new lesions at sites of trauma [1]. * **Direct Immunofluorescence (DIF):** Shows characteristic linear globular deposits of **IgM** (Colloid bodies). **References:** [1] Kumar V, Abbas AK, et al.. Robbins and Cotran Pathologic Basis of Disease. 9th ed. The Skin, pp. 1166-1170.

Question 1

A 25-year-old woman develops extensive pruritic wheals following ingestion of seafood to which she was allergic. While these lesions are usually not biopsied, a biopsy would probably show which of the following features?

Accepted Answer

Dilated superficial lymphatic channels

Answer

Granular complement and IgG at dermal/epidermal junction

Answer

Microscopic blisters

Answer

Munro microabscesses

Question 2

Histological pattern suggests the diagnosis as:

Accepted Answer

Cylindroma

Answer

Spindle cell carcinoma

Answer

Pleomorphic adenoma

Answer

Mucoepidermoid carcinoma

Question 3

A 55-year-old woman complains that the skin of her armpits and groin is progressively darkening. Physical examination demonstrates velvety brown and waxy skin in the axilla and groin. Biopsy of these lesions shows a variably hyperplastic epidermis with many sharp peaks and valleys. Aside from cosmetic considerations, what is the primary medical significance of these lesions?

Accepted Answer

They may be a sign of visceral carcinoma.

Answer

They may be a sign of immunosuppression.

Answer

They may be easily superinfected.

Answer

They may be malignant.

Question 4

Which cytokeratin is characteristically expressed in Merkel cell carcinoma?

Accepted Answer

Cytokeratin 20

Answer

Cytokeratin 7

Answer

Cytokeratin 19

Answer

Cytokeratin 18

Question 5

Which of the following is NOT a premalignant ulcer?

Accepted Answer

Bazin's ulcer

Answer

Paget's disease of nipple

Answer

Marjolin's ulcer

Answer

Lupus vulgaris

Question 6

A 50-year-old fair-skinned male presented with an elevated plaque and an ulcerated, hyperpigmented nodule with variegation of color on his back, which has been progressively increasing in size. A biopsy of the skin lesion was performed. Which of the following antibodies can be tested for this condition?

Accepted Answer

Anti-Cytokeratin antibody

Answer

Anti S100 antibody

Answer

Anti HMB45 antibody

Answer

Anti Melan-A antibody

Question 7

What are the characteristic margins of squamous cell carcinoma?

Accepted Answer

Everted

Answer

Inverted

Answer

Rolled

Answer

Undermined

Question 8

Which of the following is a poor prognostic factor for melanoma?

Accepted Answer

Spread to lymphatics

Answer

Size of tumour

Answer

Shape

Answer

Colour of tumour

Question 9

Histological clefts in Lichen planus are described as:

Accepted Answer

Max-Joseph spaces

Answer

Civatte bodies

Answer

Wickham's striae

Answer

Auspitz's sign

Question 10

What is the least common site for the spread of melanoma?

Accepted Answer

Kidney

Answer

Gastrointestinal tract (GIT)

Answer

Lungs

Answer

Liver

Dermatopathology — MCQs

Dermatopathology — MCQs

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