Adenocarcinoma in situ arising in a tubulopapillary apocrine hidradenoma of the peri-anal region.

We report the case of a 67-year-old woman who presented with a peri-anal skin tag. Histologically, the excised lesion showed features of tubulopapillary apocrine hidradenoma, with an area showing features of carcinoma in situ. The lesion also had papillary and cribriform growth patterns, reminiscent of breast lesions. Similar to vulvar lesions, peri-anal apocrine tumours are believed to arise in mammary like glands (MLGs). To the best of our knowledge, this is the first description of a peri-anal adenocarcinoma in situ arising in a tubulopapillary apocrine hidradenoma. The relationship to MLGs is also discussed.