Childhood Ki-1 lymphoma: presentation as a buttock mass.

Ki-1 lymphoma is a rare, large-cell anaplastic non-Hodgkin's lymphoma that most commonly affects older children and young adults. Presentation usually occurs as a localized infiltration of the skin and lymph nodes. We report an unusual case of childhood Ki-1 lymphoma that presented as a buttock mass in an eight-year-old girl, Pathologic evaluation revealed the characteristic lymphoma cells expressing Ki-1 antigen (CD-30), HLA-DR, interleukin 2 (CD-25), T-cell gene rearrangement, and the cytogenetic karyotype t(2;5). The patient is in complete remission following treatment with combination chemotherapy. This report broadens the clinical spectrum associated with Ki-1 lymphomas and illustrates the importance of combining routine pathologic examination with other specialized diagnostic techniques in the evaluation of childhood soft-tissue masses.