True histiocytic lymphoma. A report of four cases.

Clinical, morphologic, cytochemical, immunologic, and ultrastructural features of four cases of true histiocytic lymphoma are described. The neoplastic cells were large, ranging from 20 to 45 mu in diameter with round, folded, or convoluted nuclei, and abundant eosinophilic cytoplasm. They exhibited diffuse nonspecific esterase activity. Diffuse acid phosphatase activity was present in two cases so tested. Muramidase activity was present in half of the cases. Finely granular PAS-positive material was seen in the cytoplasm. Methyl green-pyronin positivity was variable. An occasional neoplastic cell showed erythropagocytosis in one case. Malignant cells either contained no cytoplasmic immunoglobulins (three cases) or had immunoglobulins of multiple classes (one case). Surface markers were studied in two cases; they were absent in one case, and were of multiple classes in another case. Ultrastructurally the neoplastic cells had lysosomal granules in three cases so examined, and phagolysosomes, phagocytized material and residual bodies in one of three cases so studied. Patients ranged in age from 28 to 60 years. Two patients had extralymphatic tumors. Survival of more than 5 years was seen in one patient.