Granulomatous inflammation related to amyloid deposition in a focus of multiple myeloma. Report of a case with diagnosis by fine needle aspiration biopsy.

A 61-year-old man with no prior history of serious illness presented with a lytic rib lesion. The radiographic differential diagnosis included multiple myeloma, a metastasis and a focal infectious process, such as tuberculosis or actinomycosis. Fine needle aspiration biopsy of the mass yielded an unusual smear pattern that included small lymphocytes, plasma cells, multinucleate giant cells, granulomas and amorphous eosinophilic material. These seemingly unrelated elements suggested the possibility of a chronic inflammatory lesion of bone, such as osteomyelitis, but ultimately proved to represent multiple myeloma with granulomatous inflammation related to amyloid deposition. The case demonstrates that the differential diagnosis of chronic granulomatous inflammation with numerous plasma cells, in the appropriate clinical context, includes amyloid in association with a plasma cell dyscrasia.