Pyoderma Gangrenosum‐Like Cutaneous T‐Cell Lymphoma

Abstract

A 25‐year‐old man presented with a large, undermined, violaceous ulcer with hemorrhagic crust on his nose for 1 year. It began as a “pimple”. He had similar lesions on his scalp, abdomen and groin. His sister has Crohn’s and his mother has rheumatoid arthritis. Screening blood tests and CT scans revealed no underlying disease. The clinical impression was pyoderma gangrenosum. Biopsies from the nose and abdomen revealed dense superficial and mid‐dermal perivascular lymphocytic infiltrate composed of enlarged, atypical lymphocytes with focal epidermotropism and epidermal necrosis. Immunohistochemistry revealed the infiltrate was primarily CD3 positive T‐cells without deficiency of CD4, CD7 or CD8. CD30, TIA and Granzyme were not detected. A T‐cell receptor gamma gene rearrangement was detected. Flow cytometry was negative. This is a case of pyoderma gangrenosum‐like cutaneous T‐cell lymphoma, a rare form of cutaneous lymphoma that clinically resembles PG, but histologically and immunohistochemically is cutaneous T‐cell lymphoma. Although rare, PG‐like ulcers should be added to the list of atypical manifestations of CTCL. This case highlights the need to evaluate all atypical lymphocytic infiltrates thoroughly with immunohistochemistry and gene rearrangement. The diagnosis must be made with caution as proliferative clones of lymphocytes can be found in true PG.