The correct answer is B. Most commonly presents on genitalia
Correct Answer Explanation
This is a biopsy of extramammary Paget’s disease (EMPD), which most commonly presents on the genitalia.
Incorrect Answer Explanation
Basal cell carcinoma frequently arises due to a mutation in PTCH. EMPD, if associated with an underlying GI/GU malignancy, will stain positive for CK20. EMPD does not arise from eccrine glands, rather it is an intraepithelial adenocarcinoma of the apocrine gland. Surgical excision/Mohs is considered the treatment of choice for EMPD.
Trofymenko O et al. Primary extramammary Paget’s disease of the skin: treatment and survival. Int J Dermatol. 2018 Sep;57(9):e76-e78. PubMed Link: https://www.ncbi.nlm.nih.gov/pubmed/30133752.