Diagnosis of NK and cytotoxic T-cell disorders: a review

A number of NK- and T-cell lymphomas with diverse clinical, histologic, and immunophenotypic features express one or more cytotoxic markers. Because these lymphomas are rare they can be challenging to diagnose for clinicians and pathologists. Though the common theme among the neoplasms discussed in this review is expression of one or more cytotoxic markers, expression of other markers such as cytoplasmic CD3, EBV-associated molecules, CD56, and CD30 tend to provide more important clues to the correct diagnosis. In this review, we discuss NK- and T-cell lymphomas and highlight certain key features that can aid in arriving at the correct diagnosis of these malignancies.