S-100+ lymph node neoplasm. Report of a case with histological AL and immunological features intermediate between T cell lymphoma and malignant histiocytosis.

A 16-yr-old white female was affected by continuous fever, pancytopenia with relative increase of T-8 lymphocytes, severe bone marrow hypoplasia, generalized lymphadenomegaly and splenomegaly. A first lymph node biopsy, obtained at the onset of the disease, was involved by a paracortical tumor with some S-100+ "lymphocyte-like" cells in the neoplastic areas; in the cell suspension, 70-80% of cells were E4+/E37+ lymphocytes with prevalent expression of the T-8 phenotype (52%). A second lymph node biopsy, obtained five months later, was involved by a diffuse proliferation of S-100+ cells with high mitotic activity; in the cell suspension, the majority of cells were E-/T-11+/T-3+/T-8+. At the TEM level, the neoplastic cells were characterized by regular or indented nuclei with finely dispersed chromatin and by regular or indented nuclei with finely dispersed chromatin and by irregular cytoplasmic profiles with thick pseudopodia-like projections. The possibility is discussed that this neoplasm may share some similarities with the T-gamma lymphoma being part of a poorly described group of tumors with intermediate features between T cell lymphoma and malignant histiocytosis.