Parotid gland follicular lymphoma lacking both cytoplasmic and surface light chains: a rare case.

Immunoglobulin light chain (LC) restriction is detected in the majority of B-cell non-Hodgkin lymphoma (B-NHL) by flow cytometric immunophenotyping (FCI) and serves as a surrogate marker of monoclonality. Even though it is known a small percentage of mature B-NHLs lacking surface LC, deficiency of both cytoplasmic and surface LCs has been reported in only three B-NHL cases. We report a primary parotid gland follicular lymphoma in a 63-year-old man and the lymphoma cells were deficient of cytoplasmic/surface LCs. Compared to previous reports, we used a more sensitive FCI method by combining both monoclonal and polyclonal anti-LC antibodies. Lacking LCs poses as a pitfall for the initial diagnosis of B-NHL, as well as for detecting minimal residual disease. It is important to be aware of this rare immunophenotypic aberrancy.