Muscular amyloidoma presenting as inguinal masses in multiple myeloma.

We report a case with protruding inguinal masses for 6 months, in whom muscular amyloidoma was not suspected before muscle biopsy. On pelvic magnetic resonance imaging (MRI), round masses showing peripheral rim enhancement with gadolinium were observed in iliopsoas and iliacus muscles of both inguinal areas. The same lesions were also observed in gluteus muscles. The biopsy showed Congo red positive materials in a dense fibrous background. Serum and urine electrophoresis showed Bence Jones protein, lambda type. In bone marrow section, myeloma cells were found. Peripheral blood stem cell transplantation (PBSCT) following four cycles of VAD (vincristine, adriamycin, dexamethasone) chemotherapy was performed and the result was satisfactory. Amyloidoma lesions decreased in size and number on the following MRI.