Abstract:

Cutaneous metastases from prostatic adenocarcinoma are rare. Their resemblance to cutaneous adnexal carcinomas may lead to a pitfall in diagnosis, compounded by the historic absence of robust immunohistochemical markers of prostatic carcinoma. Herein we present two relevant cases. Case 1: An 89 year old male with known recurrent prostatic carcinoma who underwent resection of a mass at the anocutaneous junction. Clinically a hemorrhoid was suspected. Microscopically, the 2.5cm polypoid nodule showed replacement of stroma/dermis by adenocarcinoma exhibiting cribriform architecture and mucin production. Cells displaying decapitation secretion prompted consideration of an apocrine carcinoma. A broad immunohistochemical panel (GCDFP, GATA3, mammaglobin, synaptophysin, chromogranin, ER, PR and S-100, AE1/AE3 and NKX3.1) revealed positivity only for the latter 2 markers. Case 2: A 71 year old male with known metastatic prostatic carcinoma presenting with a 1 month history of a 2cm pink cystic/lobulated skin lesion on the right neck. A dermatofibroma was suspected clinically. Microscopy revealed a multinodular epithelial neoplasm with cribriform architecture. Some constituent cells showed apical snouts. An immunohistochemical panel identical to that performed on case 1 again yielded positivity only for AE1/AE3 and NKX3.1. These cases highlight the fact that a deposit of metastatic prostatic adenocarcinoma in the skin can mimic a primary cutaneous apocrine carcinoma. Distinction between these entities can be made by employing NKX3.1 - a new, highly sensitive and specific, nuclear prostatic marker. Differential staining for cytokeratins (e.g., CK7-/CK20- in prostatic carcinoma and CK7+/CK20- in adnexal neoplasms) can also be valuable in this regard.

Financial Disclosure:
No current or relevant financial relationships exist.

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Phillip Moss, MBBS