Challenges and limitations of primary diagnosis of T‐cell and NK/T‐cell lymphoma in bone marrow biopsy

The diagnosis and classification of T-cell lymphomas and NK/T-cell lymphomas based on bone marrow (BM) biopsy findings alone is challenging and controversial. Primary presentation in the marrow occurs in those lymphomas where it is a main and usual site of involvement and rare examples of nodal-type T-cell lymphomas and extranodal T-cell and NK/T-cell lymphomas with isolated marrow involvement or where presentation in the marrow precedes that of extramedullary sites. In the former, there is a lack of consensus on how to classify cases that deviate from established criteria and in the latter, there is often a lack of accepted defining criteria that are applicable to BM biopsies. Therefore, the focus of the 3(rd) session of the bone marrow (BM) workshop of the 19th meeting of the European Association for Haematopathology/Society of Hematopathology in Edinburgh in 2018 was on diagnostic challenges posed by difficulties in clarifying borders between overlapping primary bone marrow T-cell and T/NK lymphoproliferations and the limitations of applying existing defining criteria related to nodal-type T-cell lymphomas and extranodal T/NK cell lymphoproliferations to isolated involvement or initial presentation in the BM.