Malignant histiocytosis with massive splenomegaly in asymptomatic patients. A possible chronic form of the disease.

Four patients with malignant histiocytosis (MH) are described whose initial manifestation of the disease was massive splenomegaly without associated systemic symptoms. The diagnosis of MH was made after histologic evaluation of splenectomy specimens. Splenomegaly in an otherwise asymptomatic patient is unusual for malignant histiocytosis, but when such a clinical picture is seen, it may be confused with other diseases that often present with massive splenomegaly and that have a similar diffuse infiltrative pattern in the spleen. Although three of these patients did eventually develop systemic symptoms characteristic of MH 3, 6, and 10 months after the detection of splenomegaly, the 15-month asymptomatic survival of one patient who received no chemotherapy suggests that MH presenting with massive splenomegaly, rather than with constitutional symptoms, may have a protracted course.