Track

Case Reports

Abstract

An 82 -year-old female with a history of perianal Paget disease likely secondary to a colorectal primary and status post excision presented to colorectal surgery with recent increased nodularity in the vicinity of the procedural scar. On clinical exam there was a raised, erythematous plaque measuring 5 cm in greatest dimension with foci of dark blue to black pigmentation and nodularity concerning for invasive melanoma. The plaque was excised and histopathologic evaluation revealed skin and squamous mucosa infiltrated by large epithelioid cells with abundant pale cytoplasms compatible with extramammary Paget disease (EMPD). By immunohistochemistry, the lesional cells stained positive for CK20, CDX2 and CK7 (patchy) and negative for P40, GCDFP and S100, confirming the diagnosis of EMPD and favoring disease secondary to colorectal malignancy. There were the additional striking features of marked reticulated proliferations of basaloid and squamoid epithelial cells emanating from the surface epidermis and frequently extending into the deep dermis. The proliferations were suggestive of benign adnexal neoplasms but were also heavily infiltrated by EMPD. In some areas, these proliferations formed large cystic structures in the deep dermis, likely accounting for the clinical impression of pigmented nodules. Histopathologic evaluation for dermal invasion by Paget cells was challenging in this setting but interpretation was aided by immunohistochemistry. This unusual phenomenon has been previously described and appears to have a predilection for perianal EMPD. Clinical and histopathologic recognition of surface epithelial proliferations in perianal EMPD is important for the proper treatment and diagnosis of this highly morbid disease.