Interdigitating Reticulum Cell Sarcoma Positive immunohistochemistry for HLA-DR and two other activation antigens, CD30(Ki-1) and CD25(IL2R).

This communication reports a case of the rare interdigitating reticulum cell (IDRC) sarcoma of lymph nodes in a 46-year-old man. Extensive immunophenotypic analysis on paraffin and frozen sections revealed positivity on the neoplastic cells for protein S-100 as well as for antigens CD1, HLA-DR, CD4, CD25 (IL2R) and CD30 (Ki-1). The simultaneous positivity for the three activation antigens CD30, HLA-DR, and IL2R, a phenomenon mostly described in H and S-R cells of Hodgkin's disease, is discussed in particular.