[Infiltrating lobular carcinoma of the breast, alveolar variant, with stromal reactive osteoclast-like giant cells. Description of a case].

Authors report a case of alveolar variant of infiltrating lobular carcinoma of the breast with stromal osteoclast-like giant cells. Immunohistochemically the carcinoma cells were reactive for EMA and Cytokeratins; osteoclast-like giant cells (OCL-GC) were negative. OCL-GC and histiocytoid mononuclear cells with nuclei similar to those within the OCL-GC present in this case, were strongly immunoreactive with KP-1, a recently developed monoclonal antibody directed against cells of mononuclear phagocytic lineage in routinely processed tissue section and showed immunoreactivity to vimentin. These findings of our case provide evidence against a carcinoma cells derivation and support a monocytic/histiocytic origin for the OCL-GC.