Abstract

Extramammary Paget disease (EMPD) of peristomal skin is an exceedingly rare occurrence of secondary involvement by gastrointestinal adenocarcinoma of the underlying intestinal tissue. Differentiating peristomal EMPD from glandular metaplasia poses a diagnostic dilemma with serious treatment implications. Special AT-rich sequence binding protein (SATB2) is an immunohistochemical stain expressed in normal colorectal epithelia and sporadic colorectal carcinomas (CRC). Loss of SATB2 expression has been observed in inflammatory bowel disease (IBD)-associated dysplasia and CRC, aiding in the differentiation between dysplastic and non-dysplastic colorectal mucosa in patients with IBD. We report a case of a 70-year-old man with a past medical history of Crohn disease with ileostomy who developed persistent, worsening erythema around his stoma. Multiple scouting biopsies showed similar findings with glandular formation within the epidermis associated with cytologic atypia and hyperchromatic nuclei. Immunohistochemistry demonstrated CK20 positivity, CK7 negativity, and diffuse loss of SATB2 by lesional cells. Based on the immunohistochemical profile along with the degree of cytologic atypia present, a diagnosis of secondary EMPD was rendered. We review the literature for additional cases of peristomal EMPD and compare histopathologic and immunophenotypic features of our case with those previously reported. Conclusions: EMPD arising in the peristomal skin has been rarely described. Loss of SATB2 expression may help to differentiate secondary EMPD of the peristomal skin from glandular metaplasia in the setting of IBD. Larger studies to validate these findings are needed.

Financial Disclosure:
No current or relevant financial relationships exist.