Correct Answer: A. CK20

Explanation: Extramammary Paget’s Disease is an intraepithelial adenocarcinoma of apocrine glands that presents with a well-demarcated erythematous plaque in the genital area. Histologically, pagetoid cells stain positive for CK7, unlike pagetoid melanoma cells which stain positive for S100. CK20 staining has been associated with secondary EMP in the setting of underlying gastrointestinal or genitourinary carcinoma.

Reference: Ohnishi T, Watanabe S. The use of cytokeratins 7 and 20 in the diagnosis of primary and secondary extramammary Paget’s disease. Br J Dermatol. 2000;142:243-7.

Don’t Agree? Tell us why in the comments section below.

Test your knowledge with custom quizzes at Derm In-Review or check out more pop quizzes.

Brought to you by our Brand Partner