Bone Marrow Histology in Hemophagocytic Lymphohistiocytosis

Bone marrow (BM) samples are obtained through aspiration and trephine biopsy. Hemophagocytic lymphohistiocytosis (HLH) has been largely studied in BM aspirate smears.

To investigate the histologic features of HLH in trephine biopsy.

Patients with hemophagocytosis in BM aspirate smears were assigned to HLH (n = 127) and non-HLH (n = 203) groups. We quantified hematoxylin-eosin and CD68 immunohistochemical staining of their trephine biopsies.

No significant correlation was noted in the hemophagocytosis count between aspirate smears and trephine biopsies. Compared with the non-HLH group, the HLH group had a higher hemophagocytosis count (13 versus 9 per tissue section, P = .046), lower percentage of the adipocytic area (36.7% versus 50.3%, P < .001), and higher percentage of the foamy area (19.1% versus 14.5%, P < .001). The HLH group had more histiocyte infiltrates (total histiocyte density, 9.2% versus 7.3%; P < .001) and more fat-infiltrating histiocytes (histiocyte density of the fat-associated part [HD-FA], 7.6% versus 6.2%; P < .001). We identified the following poor prognostic factors in the HLH group: age 50 years or older (median overall survival [mOS], 95 versus 499 days; P = .04), Epstein-Barr virus-positive T-cell lymphoproliferative diseases (EBV+TLPDs) (mOS, 51 versus 425 days; P < .001), hemophagocytosis count of 6 or higher per tissue section (mOS, 66 versus 435 days; P = .02), and HD-FA of 9% or greater (mOS, 61 versus 359 days; P = .02). Multivariate analysis revealed that age 50 years or older (hazard ratio [HR], 2.38; P < .001), EBV+TLPDs (HR, 2.07; P < .001), and hemophagocytosis count of 6 or higher per tissue section (HR, 2.07; P = .002) were independent prognostic factors for HLH.

The HLH group had higher hemophagocytic activity, higher cellularity, a more foamy appearance, more histiocyte infiltrates, and more fat-infiltrating histiocytes. High hemophagocytic activity and marked histiocyte infiltrates in the BM fat were associated with poorer prognosis.