Background: Solitary plasmacytoma of bone (SPB) is a rare plasma cell neoplasm. It arises in bone as a single locus in the absence of any plasma cell myeloma lesions. Plasma cell neoplasms intrinsically express only one immunoglobulin light chain (IgL)-kappa or lambda-and using this fact, kappa/lambda deviation is the decisive factor for diagnosis. Co-expression of both IgLs in a single tumor cell is extremely rare.
Case presentation: We report a case of SPB that arose in the vertebra of a 52-year-old Japanese woman. Histologically, the resected mass showed diffuse plasma cell proliferation. Dual IgL expression was detected by flow cytometry, immunohistochemistry, and in situ hybridization (ISH) targeting IgL mRNA.
Conclusion: We have presented an extremely rare case of SPB showing dual expression of kappa and lambda IgLs. This unusual case of plasma cell neoplasia might represent a possible exceptional example of failure of "IgL isotypic exclusion."
Keywords: Allelic exclusion; Case report; Dual immunoglobulin light chain expression; Isotypic exclusion; Solitary plasmacytoma of bone.
© 2021. The Author(s).