Bone marrow manifestations in multicentric Castleman disease

Summary This study aimed to document the morphological and immunophenotypic features, and describe the diagnostic features of bone marrow ( BM ) involvement in human herpes virus 8 Multicentric Castleman disease ( HHV 8‐ MCD ). BM trephine biopsy ( BMTB ) specimens from 28 patients were revisited. Samples were evaluated for expression of CD 3, CD 20, CD 138, CD 68R, glycophorin C, CD 42b, HHV 8‐latency‐associated nuclear antigen ( LANA 1), Epstein–Barr virus‐encoded small RNA and light chains. Presence of significant numbers of HHV 8‐ LANA 1 + lymphoid/plasmacytic cells, noted in 10/28 cases, was indicative of BM involvement and was associated with low CD 4 and CD 8 counts in peripheral blood. The characteristic morphological appearance of MCD seen in lymph nodes is a rare finding in BMTB . 4/5 cases with lymphoid aggregates were involved by MCD , whereas 6/23 cases without lymphoid aggregates were involved by  MCD ( P  = 0·023). 9/18 cases with hypercellular marrow were involved by MCD , whilst only 1/8 cases with normo/hypocellular marrow showed involvement by MCD ( P  = 0·070). While 9/21 cases with increased marrow reticulin were involved by MCD , none of the cases with no increase in reticulin were involved by MCD ( P  = 0·080). Reactive plasmacytosis is a frequent finding. We conclude that bone marrow is involved in a significant proportion of patients with MCD (36%), and involvement can be identified by HHV 8‐ LANA 1 immunohistochemistry.