Adult Ki-1-positive large cell anaplastic lymphoma presenting with skin lesions.

We describe an adult case of anaplastic large cell lymphoma who presented with nonepidermotropic skin lesions histologically simulating malignant histiocytosis. The patient later developed systemic symptoms and peripheral lymphadenopathy. B- and T-cell markers and the Leu-M1 antigen were absent from immunohistochemically investigated skin lesions and lymph nodes. The expression of Ki-1 antigen by most tumor cells was the distinctive immunologic character of this disorder which helped to clarify the pathological diagnosis. The unusual clinical, pathologic, and immunologic features of this patient represent the adult counterpart of a clinicopathologic syndrome, so far described in children and adolescents, of Ki-1 lymphoma presenting with skin lesions and peripheral lymphadenopathy. Prompt recognition of this disorder and early delivery of chemotherapy seem important to improve prognosis.