Current lymphoma diagnostic standards: the pathologists’ view

This short review aims at summarizing the current standards of lymphoma diagnostics and some novelties in the recent WHO classification. The importance of close collaboration between clinicians and pathologists to render the correct diagnosis and to find the most appropriate treatment for each individual patient is highlighted. In lymphomas, the diagnostic evaluation of histopathology, immune phenotype and genetics are puzzle pieces that have to be put into a broader context with the help of the information given by the clinical colleagues, such as patient’s age and sex, location of the lesion, previous medical history and medication. An excision of the affected lymph node is always preferable to fine needle biopsies, as—in many instances—only the evaluation of the whole specimen allows for reliable diagnosis, grading and additional investigations.

The new WHO classification entailed many changes in the category of diffuse large B‑cell lymphoma and high-grade B‑cell lymphoma. The obligatory specification of the cell of origin in diffuse large B‑cell lymphoma is obtained via additional immunohistochemical stainings. The identification of high-grade B‑cell lymphomas with genetic double/triple hits, requiring a more aggressive management, can only be achieved by the detection of chromosomal translocations (MYC, BCL2 and/or BCL6). Significant changes in the classification of T‑cell lymphomas have occurred due to the recognition of the follicular T‑helper cell origin in some instances, and sharpening diagnostic borders of intestinal T‑cell- and Epstein-Barr-virus-associated proliferations. Finally, the discovery of disease-defining and/or prognostically relevant mutations makes the introduction of proper routine molecular testing mandatory.