Spindle cell neoplasms of lymph nodes of probable reticulum cell lineage. True reticulum cell sarcoma?

Primary spindle cell neoplasms involving hematolymphoid organs are extremely rare. We present four cases of spindle cell neoplasms of unusual phenotype arising within lymph nodes. Two of the four cases showed morphologic and immunophenotypic features suggestive of interdigitating reticulum cell lineage; these cases expressed several macrophage antigens and S-100 protein but not CD1. The other two cases showed evidence suggestive of dendritic reticulum cell lineage. Both cases expressed HLA-DR, several macrophage antigens, complement receptors C3b and C3d; one case expressed R4/23; both showed the presence of desmosomes on ultrastructural examination. A germline configuration for the immunoglobulin heavy chain and beta-T--cell receptor genes was detected in all four cases. Of the two patients in the first group, one had local recurrence of tumor; the other died of widespread metastases. Of the two patients in the second group, both are alive and well at 12 and 27 months follow-up, respectively.