REGRESSING ATYPICAL HISTIOCYTOSIS, A REGRESSING CUTANEOUS PHASE OF KI-1-POSITIVE ANAPLASTIC LARGE CELL LYMPHOMA - IMMUNOCYTOCHEMICAL, NUCLEIC-ACID, AND CYTOGENETIC STUDIES OF A NEW CASE IN VIEW OF CURRENT OPINION

Background. Regressing atypical histiocytosis is a rare multifocal cutaneous tumor characterized by large, spontaneously regressing, ulcerating skin nodules. Although initially self-remitting, the condition may progress to systemic lymphoma. Methods. Using material from one patient, an attempt was made to clarify the nature of this condition with immunophenotyping, genotyping, and chromosome studies. Results. Immunophenotyping studies indicated the condition was of T-cell lineage, although T-cell receptor gene studies showed polyclonal rearrangement. This case progressed to systemic lymphoma. Conclusions. The authors believe regressing atypical histiocytosis is a regressing phase of Ki-1-positive anaplastic large cell lymphoma of the skin.