Zebras and hen's teeth: recognition and management of rare T and NK lymphomas.

Although all the peripheral T-cell lymphomas are uncommon, there are some entities that are truly rare. Subtypes, such as enteropathy-associated T-cell lymphoma, hepatosplenic T-cell lymphoma, extranodal NK/T-cell lymphoma, and subcutaneous panniculitis-like T-cell lymphoma, have an approximate annual incidence in United States of <500 each. In these very rare subtypes, there is limited data to guide clinical decision-making. As such, our treatment decisions are often based on extrapolation, case series, personal experience, and biases. We summarize the existing data regarding initial management of these entities and compare how that management follows paradigms established for the more common T-cell lymphomas.