Modern Approach to Nodal T-Cell Lymphomas.

In recent decades, there have been many meaningful contributions to the pathology literature with respect to T-cell lymphoma pathogenesis and biology and improved diagnostics. We know more about disease classification, clinical characteristics, immunophenotype, and genetics than ever before, and yet diagnosis of nodal T-cell lymphomas continues to be a challenging exercise. Complicating interpretation are the many non-neoplastic mimickers of peripheral T-cell lymphoma including drug effects, viruses, autoimmune, and idiopathic conditions, that must be considered when faced with an abnormal lymph node biopsy. The number of immunohistochemical stains required to make a diagnosis of T-cell lymphoma is not standardized and may be exhaustive, requiring judicious use of tissue sections. Clonality studies may contribute to the diagnosis, though questions remain about test modality, when to exercise interpretive caution, and what to do if a clone cannot be demonstrated. Use of next generation sequencing in the diagnosis of nodal T-cell lymphomas is increasing, but how the data can be practically applied to diagnosis is still under examination. The goal of this paper is to consider nodal T-cell lymphoma diagnosis and classification in a modern context, using a question-and-answer format to capture the interest of the reader and address common pathology consultation queries.