CYTOKERATIN IN ANAPLASTIC LARGE-CELL LYMPHOMA

A B-cell anaplastic large cell lymphoma, confirmed by immunohistochemi stry and Southern blot immunoglobulin gene rearrangement analysis, con tained neoplastic cells that were immunoreactive for cytokeratin using antibodies CAM 5.2, M20, MAK 6, and KS-B17.2. Bands corresponding to cytokeratin 18 and cytokeratins 18 and 8 were seen on Western blot imm unoanalysis using antibodies KS-B17.2 and CAM 5.2. The lymph node also contained cytokeratin-positive extrafollicular fibroblastic reticulum cells. Although it is possible that the presence of cytokeratin in th e cells of anaplastic large cell lymphoma represented phagocytosed fil aments from the reticulum cells, it is more likely that the cytokerati ns were synthesized by the malignant cells. The finding of cytokeratin in anaplastic large cell lymphoma, although infrequent, adds to the c onfusion in the diagnosis of this pleomorphic neoplasm.