Plasma cell neoplasm with papillary architecture mimicking carcinoma

Plasma cell neoplasm with papillary architecture mimicking carcinoma
Author: Jiani Chai; Fitra Rianto; Yanhua Wang
Category: Lymphoma: Mature B-cell and Plasma cell Neoplasms > Plasma Cell Neoplasm > Plasma cell myeloma
Published Date: 05/19/2023

A 65-year-old female with a past medical history of IgG lambda multiple myeloma and ductal carcinoma in situ of the breast presented with right shoulder pain and paresthesia. Imaging showed small lytic lesions within the C5 and C6 vertebral bodies and a large lytic lesion within the T1 vertebral body with epidural extension and mild compression of the spinal cord. A vertebral body biopsy revealed sheets of neoplastic cells with pleomorphic, hyperchromatic nuclei, irregular nuclear membrane contour, and scant pale cytoplasm. Some cells had distinct nucleoli. There was no obvious mature plasma cell morphology present. These cells formed papillary architecture with fibrovascular core (panels A and B; original magnification ×20 and ×40; hematoxylin and eosin stain). There was an increase of mitosis and apoptosis. On immunohistochemical staining, the neoplastic cells were positive for CD138 and lambda light chain (panels C and D; original magnification ×40; CD138 and lambda immunostain); negative for cytokeratin (AE1/AE3 and CAM 5.2). Ki-67 and MUM-1 showed patchy stains, suggestive of decalcification effect. The other negative markers were BCL1, HHV8, and GATA3. Overall, these findings support the diagnosis of plasma cell myeloma. Plasma cell neoplasm can exhibit a variety of cytological and architectural heterogeneity. Here, we report this unusual case with papillary architecture that mimicked carcinoma morphologically. However, the phenotypical features were characteristic, and diagnosis was rendered based on immunophenotype.