Lambda light chain predominance as a sign of emerging lymphoma.

Immunohistologic methods can be used to help differentiate inflammatory from neoplastic lymphoid proliferations in extranodal sites. The majority of B-lymphocytes in an inflammatory process should show surface or cytoplasmic staining for kappa light chains, reflecting the normal human kappa:lambda ratio of approximately 2:1. If a benign-appearing lesion is found to contain predominantly lambda-positive cells, this may be a sign of an emerging lymphoma. The principle is illustrated by a case report of a lymphoid "pseudotumor" of the orbit that showed a polyclonal staining pattern with a predominance of lambda-positive cells and subsequently developed into a lymphoma-producing IgM lambda.