Microscopic description:

Lesion consist of plasmacytoid cells

Cells are positive for CD138 and MUM1 by immunostaining and negative for AE1/AE3 and GATA3

The findings are suggestive of a Plasma cell neoplasm consistent with plasmacytoma. The patient has a history of multiple myeloma

Discussion:

Extra medullary Plasmacytoma in patients with multiple myeloma are detected in up to 10-22% of the cases. The involvement could be caused by direct growth from the skeletal lesions or via haematogenous route

Lesion may present as single or multiple nodules, commonly seen in skin, liver, breast, kidney, CNS and pleural membrane

Although reported in literature, the involvement of bladder is rare

The prognosis for patients with extra medullary involvement is poor

A histological differential diagnosis includes plasmacytoid urothelial carcinoma that shows discohesive cells that resemble plasma cell infiltrate. Unlike Plasmacytoma, these cells stain positive for cytokeratin but can also express CD138. Clinical and laboratory correlation is warranted to establish diagnosis

References:

Rosiñol L, Beksac M, Zamagni E, et al. Expert review on soft-tissue plasmacytomas in multiple myeloma: definition, disease assessment and treatment considerations. Br J Haematol. 2021;194(3):496-507. doi:10.1111/bjh.17338

Khaliq W, Uzoaru I, Konchanin RP, Sapiente RA, Egner JR. Solitary extramedullary plasmacytoma of the bladder: a case report and literature. Oncology (Williston Park). 2010 Aug;24(9):832-5.

Wadhwa K, Singh R, Solomon LZ. Bladder extramedullary plasmacytoma and synchronous bladder urothelial transitional cell carcinoma: A case report and review of the literature. Open Access J Urol. 2011;3:25-27. Published 2011 Feb 15. doi:10.2147/OAJU.S10897

He J, Yue X, He D, et al. Multiple Extramedullary-Bone Related and/or Extramedullary Extraosseous Are Independent Poor Prognostic Factors in Patients With Newly Diagnosed Multiple Myeloma. Front Oncol. 2021;11:668099. Published 2021 Jul 7. doi:10.3389/fonc.2021.668099

Perrino CM, Eble J, Kao CS, et al. Plasmacytoid/diffuse urothelial carcinoma: a single-institution immunohistochemical and molecular study of 69 patients. Hum Pathol. 2019;90:27-36. doi:10.1016/j.humpath.2019.04.012

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