ABPath Dermatopathology 3

Question 1

Which molecular alteration is found in approximately 40–60% of cutaneous melanomas arising on intermittently sun-exposed skin?

Accepted Answer

BRAF V600E mutation

Answer

KIT mutation

Answer

NRAS mutation

Answer

NF1 loss-of-function mutation

Question 2

A compound melanocytic lesion shows large epithelioid cells with abundant cytoplasm containing fine 'dusty' melanin pigment arranged in nests, with a pushing border into the deep dermis but no significant atypia or mitoses. This best describes:

Accepted Answer

Deep penetrating nevus

Answer

Nodular melanoma

Answer

Cellular blue nevus

Answer

Reed (pigmented spindle cell) nevus

Question 3

The t(X;18)(p11;q11) translocation producing an SS18-SSX fusion gene is the defining molecular alteration of:

Accepted Answer

Synovial sarcoma

Answer

Kaposi sarcoma

Answer

Epithelioid sarcoma

Answer

Clear cell sarcoma of soft tissue

Question 4

Donovan bodies (Klebsiella granulomatis within macrophages) in granuloma inguinale are best demonstrated with:

Accepted Answer

Giemsa stain

Answer

Ziehl-Neelsen stain

Answer

Periodic acid-Schiff (PAS)

Answer

Grocott methenamine silver (GMS)

Question 5

A skin biopsy from an HIV-positive patient shows lobular capillary proliferation with plump endothelial cells, neutrophils, and granular eosinophilic material best identified by Warthin-Starry stain. This is most consistent with:

Accepted Answer

Bacillary angiomatosis

Answer

Kaposi sarcoma

Answer

Pyogenic granuloma

Answer

Angiosarcoma

Question 6

Clark's levels of melanoma invasion differ from Breslow thickness in that Clark's levels classify depth based on:

Accepted Answer

Anatomic skin layers penetrated

Answer

Measured tumor thickness in millimeters

Answer

Percentage of cells showing mitoses

Answer

Degree of lymphovascular invasion

Question 7

Which immunohistochemical staining pattern is most characteristic of Merkel cell carcinoma and helps distinguish it from metastatic small cell carcinoma of the lung?

Accepted Answer

Dot-like CK20 positivity with TTF-1 negativity

Answer

Diffuse CK7 positivity with CK20 negativity

Answer

Diffuse S100 positivity with synaptophysin negativity

Answer

Membranous CD20 positivity with CK20 negativity