This young man presented with an exophytic and ulcerated lesion on his lower leg. Clinically, an inflammatory process such as pyoderma gangrenosum was considered, with malignancy lower on the differential diagnosis due to his age. The lesion had been fairly rapidly increasing in size. Anaplastic large cell lymphoma (ALCL) is fairly uncommon, but not rare in children. It is defined histologically by large pleomorphic cells, usually with some T-cell markers (CD2, CD5, CD4, others +/-), and with strong CD30 positivity, as in this case. It falls within the CD30+ lymphoproliferative disorders, including lymphomatoid papulosis and transformed mycosis fungoides. This patient had a solitary ulcerated mass, suggesting a diagnosis of ALCL. This patient's tumor was ALK-1 negative, a marker, when positive, associated with some systemic ALCLs. The prognosis is usually pretty favorable in tumors limited to the skin.
There is an ulcerated lesion. An infiltrate is in the dermis, accentuated in a perivascular pattern. At low power, the cells in the infiltrate appear large and mononuclear.