Anaplastic large cell lymphoma: an unusual presentation in a 7-year-old girl.

Anaplastic large cell lymphoma (ALCL) accounts for 10% to 30% of all childhood lymphomas and approximately 5% of all non-Hodgkin's lymphoma. ALCL is considered to be a T-cell non-Hodgkin's lymphoma that can be divided into two major groups with distinct genetic, immunophenotypic, and clinical behaviors. The first group consists of a spectrum of CD30+ T-cell lymphoproliferative disorders that include primary cutaneous ALCL (C-ALCL) and lymphomatoid papulosis. The second group is systemic ALCL (S-ALCL), which is further divided into two subgroups: anaplastic lymphoma kinase positive (ALK+) and ALK-negative. Between 30% and 60% of S-ALCL express ALK, which is usually the result of a t(2;5) translocation that correlates with onset in the first three decades of life, male predominance, and good prognosis. Although morphologically similar, ALK- ALCL shows varied clinical behaviors and immunophenotypes; is commonly seen in older age groups, with a peak incidence in the sixth decade of life with no preference as to sex; and has an overall poorer prognosis. We present a case of CD30+, ALK- S-ALCL in a 7-year-old girl.