71-year-old man was hospitalized for altered mental status and was found to have right upper lobe pneumonia and acute renal failure. Lab studies revealed severe hypercalcemia at the level of 19 mEq/L and increased CRP (35.5 mg/L). Radiological findings were significant for extensive diffuse myelomatous lytic lesions in calvarium, pelvic bones and spine including a large destructive lesion of the L2 vertebral body. A bone marrow aspiration yielded 65% of plasma cells showing profound cellular and nuclear polymorphism. Cellular pleomorphism was characterized by small plasma cells with lymphoid morphology, multinucleated larger plasma cells and huge plasma cells with hyper segmented nuclei (panels A, B). Atypical mitotic figures were easily identified (panels C, D, E). An immunohistochemical stain for CD138, and in situ hybridization studies for kappa and lambda light chains performed on core bone marrow biopsy revealed lambda – restricted plasma cells in large aggregates suggesting that this is a variant of plasma cell myeloma with sarcomatoid morphology. Ki- 67 /MIB-1(panel F). FISH analysis detected del(17p13.1), t(4;14)(p16.3;q32) and monosomy 13. Conventional cytogenetics revealed complex abnormal male chromosome, characteristic of multiple myeloma. Flow cytometric analysis of DNA and cytoplasmic immunoglobulin (cIg) revealed discretely hypodiploid and hypotetraploid DNA content with lambda light chain excess in 44% with cIg index of 4.4 and 7.8. Immunophenotypic analysis revealed plasma cell population expressing CD45 (dim), CD138, and CD56. Majority of the plasma cell neoplasms are easily identified based on classic plasmacytoid morphology of the neoplastic cells. However, some of the morphological variants with unusual cytological and architectural features can lead to misdiagnoses including anaplastic carcinoma or lymphoma. Pleomorphic variant with sarcomatoid morphology is a rare variant of plasma cell tumors which exhibits marked cellular and nuclear pleomorphism. Awareness of rare sarcomatoid variant of malignant plasma cells is essential in recognizing unusual plasma cell tumors.