Aims This study aimed to evaluate the key features of bone marrow trephine (BMT) biopsy involvement by lymphoma.

Methods 511 cases were assessed for percentage of marrow involvement, pattern of involvement (diffuse, nodular, paratrabecular, interstitial or intrasinusoidal), presence/absence of granulomas, stromal fibrosis and necrosis, presence/absence of neoplastic/reactive follicles and discordance with other biopsy sites. Correlation with aspirate and peripheral blood findings was made in a subset of 345 patients (167 aspirates, 178 blood).

Results The most frequent subtype was follicular lymphoma (26.2%) followed by extranodal marginal zone (23.1%), lymphoplasmacytic (19.2%), diffuse large B cell (DLBCL) (12.5%), Hodgkin (HL) (5.7%) and mantle cell lymphomas (4.3%). The predominant pattern in follicular lymphoma was paratrabecular. Marginal zone lymphomas of all types and lymphoplasmacytic lymphoma showed a relatively even distribution between diffuse, interstitial, paratrabecular and nodular patterns. The majority of mantle cell lymphoma cases showed either diffuse or nodular patterns. A diffuse pattern was common in DLBCL and Burkitt lymphomas. An intrasinusoidal pattern was seen only in extranodal and splenic marginal zone lymphomas. Granulomas and fibrosis were uncommon in small cell B cell lymphomas but frequent in DLBCL and HL. Aspirate and trephine results concurred in 73.8% of cases overall, but this varied widely between subtypes. Peripheral blood involvement rates by lymphoma also varied, with a mean of 37.1%.

Conclusions Different lymphomas often demonstrate reliably characteristic architectural patterns of marrow involvement which can help differentiate them even when cytological features do not permit this, and marrow stromal and other background changes may also be useful pointers towards a particular lymphoma subtype.