Neoplasms arising from precursor lymphoid cells committed to the B-cell or T-cell lineage can present primarily in the bone marrow (BM), blood (i.e. leukaemic presentation) or at extramedullary tissue sites (i.e. lymphomatous presentation) (Table 14.1). Hence, these neoplasms are appropriately termed as B- or T-lymphoblastic leukaemia/lymphoma [1, 2].

The classification of mature neoplasms has evolved over the years, with the current WHO classification based largely on the genetics and cellular origin of lymphoid neoplasms [1]. Clinical behaviour of lymphoid neoplasms, however, continues to play an important role in defining disease entities. Mature lymphoid neoplasms in the case of leukaemias primarily involve blood and bone marrow (BM), while in lymphomas, most entities, with an occasional exception (e.g. Waldenström macroglobulinaemia/lymphoplasmacytic lymphoma) show predominant involvement of extramedullary sites/site with secondary involvement of the bone marrow (BM). In patients with lymphomas, the BM may be biopsied as part of staging (e.g. follicular lymphoma) or when the primary site of involvement is not amenable to biopsy (e.g. primary splenic lymphomas such as splenic marginal zone lymphoma or hepatosplenic T-cell lymphoma). Less commonly, a mature lymphoid neoplasm may be an unexpected or suspected diagnosis initially made on BM biopsy (BMB) performed during investigation of B-symptoms or unexplained cytopaenias.