Ki-1+ anaplastic large cell lymphoma in a child with unpredictable clinical course.

Ki-1+ anaplastic large cell lymphoma (Ki-1+ ALCL) is a subtype of non-Hodgkin lymphoma (NHL) with defined histopathological characteristics but with highly variable clinical presentation and outcome. Although in most of the patients the disease behaves as an intermediate- or high-grade lymphoma, some patients present with an indolent clinical course. Factors that determine the clinical behavior of this lymphoma have not yet been identified. A case is reported of a 13-year-old girl who initially presented with Ki-1+ ALCL but later developed recurrent localized cutaneous disease and followed a clinical course similar to that of a low-grade lymphoma.