Immunoperoxidase staining of cytoplasmic immunoglobulins. A diagnostic aid in distinguishing cutaneous reactive lymphoid hyperplasia from malignant lymphoma.

A method for staining cytoplasmic immunoglobulins utilizing an immunoperoxidase technic on paraffin-embedded tissue was used to examine two cutaneous lesions. On routine hematoxylin-eosin staining, one lesion exhibited what appeared to be a mixed population of mature cell types and was therefore interpreted as reactive lymphoid hyperplasia, whereas the other lesion showed a uniform population of immature cells and was interpreted as a malignant lymphoma. Immunoperoxidase staining supported these interpretations since the reactive lesion showed polyclonal IgG lambda and kappa staining, and the malignant lymphoma monoclonal staining with IgG lambda. In selected material, immunoperoxidase staining can distinguish a truly mixed population of cell types (probably benign) from a monoclonal population of cells exhibiting either uniform or mixed morphologic configurations associated with B lymphocyte transformation (probably malignant).