Familial hemophagocytic lymphohistiocytosis.

The cytologic features of familial hemophagocytic lymphohistiocytosis in two infant siblings were reviewed and compared to the histopathologic features in the same cases. The cytologic features of familial hemophagocytic lymphohistiocytosis in imprint smears from the spleen, lymph nodes, and liver were distinct, with proliferation of benign histiocytes engulfing erythrocytes and platelets. Hemophagocytic activity was more readily identifiable in imprint smears than in paraffin-embedded histologic sections. The differential diagnosis of histiocytic proliferative syndromes is also discussed.