Plasma cell lesions of the head and neck: immunofluorescent determination of clonality from formalin-fixed,...

An immunofluorescent technique was used on formalin-fixed, paraffin-embedded tissue to characterize and diagnose plasma cell lesions of the head and neck. Infiltrates were classified as either monoclonal or polyclonal with rhodamine and fluorescein staining of light chains and heavy chains. In the cases in which histopathologic diagnoses were relatively certain, immunofluorescence provided good correlation. In those cases in which histopathologic diagnoses were equivocal, immunofluorescence distinguished between reactive and neoplastic infiltrates through the determination of clonality of the infiltrates.