Atypical morphological cases of plasma cell neoplasm is very challenging for interpretation. Hence clinical features along with additional utility of available ancillary tests is important in diagnosis of  such a cases.  we are describing different morphological presentation of myeloma where plasma cells showed atypical morphology, leading to varied differential diagnosis. However clinical features with immunophenotyping (IPT) by flowcytometry / immunohistochemistry(IHC) in adjunct to serum electrophoresis, immunofixation and free light chain assays confirmed the diagnosis

Case 01: Auer rod-like inclusions in myeloma are composed of crystalline depositions of lysosomal enzymes.  This phenomenon is exclusively found in myeloma with kappa-type paraprotein. This case showed multiple auer rod like inclusion and showed kappa type paraprotein restriction as similar to literature.

Reference: Auer rod-like intracytoplasmic inclusions in multiple myeloma. A case report and review of the literature, Int. Jnl. Lab. Hem. 2009 Apr;31(2):236-40

Case 02: Small lymphocyte like MM is a rare, morphologically challenging variant distinguished from B-cell lymphoma by lack of CD45 and presence of CD138 and the clinical presentation of MM. Second case showed small lymphocyte like morphology. IPT showed strongly expressed CD138:95.7% and CD38: 97.9%. IHC of plasmacyotid lymphoid cells in the bone marrow showed strong positivity for CD 138 and MUM 1 with lambda light chain restriction.

Reference: Clinical, Immunophenotypic, and Genetic Characterization of Small Lymphocyte–Like Plasma Cell Myeloma, Am J Clin Pathol 2010;133:265-270 DOI: 10.1309

Case 03: Peripheral smear showed numerous atypical cells with hairy like projection. This was a case of plasma cell leukaemia. BM was solidly cellular and replaced by these cells. Immunohistochemitrsy showed CD138 positive cells in the bone marrow with kappa type paraprotein restriction. Immunophenotyping strongly expressed CD 38 and CD 138 co-positivity.

Reference: A case of primary plasma cell leukemia with hairy-cell morphology and lambda-type Bence-Jones protein. Immunohistochemical and molecular analysis. Jpn J Clin Oncol 2003.

Case 04: About 90% of crystal storing histiocytosis is associated with plasma cell dyscrasia. It is the result of a phagocytic defect which leads to excess accumulation of the paraproteins or immunoglobulin crystals in the lysosomes of the histiocytes resulting in crystal storing histiocytosis. This case BM aspirate had poor cell trails and showed 5% mature plasma cells with crystal storing histiocytes. But trephine biopsy showed nodular and interstitial infiltrates of plasma cells including occasional immature forms. Intertrabecular aggrgetaes of histiopcytes also seen. IHC with CD 38 highlighted plasma cells and kappa paraprotein restriction.

Reference: Dogan S, Barnes L, Cruz-Vetrano WP. Crystal-storing histiocytosis: report of a case, review of the literature (80 cases) and a proposed classification.Head Neck Pathol. 2012 Mar;6(1):111–20.

Case 05: Anaplastic myeloma may mimic high grade lymphoma, acute myeloid leukemia, metastatic tumour deposits, monocytoid cells, immunoblast like cells and rarely dysplastic megakaryocytes. Anaplastic myeloma is a rare with poor prognosis. Similar to literature fifth case had anaplastic morphology which `showed dysplastic megakaryocytes like morphology which were positive for MUM-1 and showed inversion 19 in 21 metaphases. Fluorescence in situ hybridization (FISH) showed deletion (17p).

Reference: Pleomorphic Multinucleated Plasma Cells Simulating Megakaryocytes in an Anaplastic Variant of Myeloma, Turk J Haematol. 2018

Case 06: Intracytoplasmic azurophilic granules are a very rare histologic finding that usually result from deposition of excess immunoglobulin. Sixth case bone marrow aspirate showed plasmacytosis including immature forms with numerous azurophilic like granules. Trephine biopsy showed aggregates of plasma cells including immature forms. IHC CD38 highlighted these plasma cells.

Reference: Barbara J. Bain  Wenchee Siow  Amin Rahemtulla  Saad Abdalla. Azurophilic granules in myeloma cells,  American Journal of Hematology, 17 December 2013.

Case 07: Seventh case bone marrow aspirate showed atypical cells with popcorn like morphology and trephine biopsy showed moderately hypercellular marrow with marked plasmacytosis including aggregates. CD138 highlighted the plasma cells. This morphology not described previously in literature.