Rare case of plasma cell myeloma with megakaryoblastic morphology mimicking acute leukemia

Myeloma plasma cells vary from mature forms to immature, plasmablastic, and pleomorphic cells. Only a few cases of morphologic variant of plasma cell neoplasm have been reported, in which the plasma cell neoplasm presented with lymphoplasmacytic, megakaryocytic, plasmablastic, lymphocytosis-like, and variant hairy cell leukemia-like morphological features. A 66-year-old man sought medical attention with a previous 2-month history of lower back and chest pain. Magnetic resonance imaging (MRI) of the thoracic spine showed thoracic vertebral body shape and disc degeneration, and bone lesion. Blood work showed mild anemia (hemoglobin, 101 g/L; white blood cells, 6.98 × 10⁹/L; platelets, 146 × 10⁹/L.), hyperuricemia (UA 671 umol/L), and immunoglobulin G kappa [IgG(κ)] paraproteins. Bone marrow study revealed diffuse invasion by sheets of megakaryoblast-like cells. Flow cytometric analysis and bone marrow biopsy revealed plasma cell myeloma (PCM), and thoracic puncture biopsy indicated plasma cell neoplasms. Overall, the findings were in accordance with a PCM. To date, this is the first reported case of PCM with megakaryoblastic morphology mimicking acute leukemia. Recognizing the morphological variant of PCM is important in differentiating it from acute leukemia.