Morphological Criterion for Daignosis:

Hemophagocytosis is the only histomorphological criterion in diagnosis of hemophagocytic lymphohistiocytosis (HLH), is not sensitive or specific alone.

Gars E et al (2018) studied 78 patients with hemophagocytosis (40 with HLH and 38 without HLH) demonstrated that

“non-nucleated erythrophagocytosis alone is a non-specific finding,

hemophagocytosis of granulocytes [1 per 1000 cells, area under the curve (AUC): 0.92, 95% Confidence Interval (CI): 0.86, 0.99], nucleated erythrocytes (4 per 1000 cells, AUC: 0.92, 95%CI: 0.87, 0.98), and at least one hemophagocyte containing multiple nucleated cells (AUC: 0.91, 95%CI: 0.85, 0.95) are strongly associated with HLH.

Joint modeling of hemophagocytes containing engulfed granulocytes, nucleated erythrocytes, and lymphocytes effectively distinguished between HLH and non-HLH (cross-validated AUC: 0.90, 95%CI: 0.83, 0.97).”