Anaplastic multiple myeloma- A diagnostic dilemma

Anaplastic myeloma (AM) represents a rare and aggressive variety of multiple myeloma (MM) which is morphologically composed mainly of immature plasma cells with nuclear enlargement and multilobulation. This variant can be confused with high grade lymphoma, metastatic carcinoma or even with dysplastic megakaryocytes in bone marrow study, posing a diagnostic challenge. Here, we present a case of a 71 years old male with complaints of body ache, progressive weakness for a month and a recent history of fall causing 7th and 10th rib fractures. Biochemical examination revealed raised serum calcium, LDH, 24 hour urinary protein, raised lambda on serum free light chain assay and marginally high serum creatinine. PET- CTS revealed lytic lesions involving multiple long and flat bones. Bone marrow aspirate showed 81% large anaplastic cells with marked nuclear convolution. Immunophenotying showed positivity for CD38, CD138, CD56 along with lamda restriction. Composite consideration of clinical features, biochemical investigations, hematological workup and immunophenotyping led to a final diagnosis of anaplastic multiple myeloma.