Spleen findings in generalized mastocytosis. A clinicopathologic study.

BACKGROUND

Little information regarding the morphologic findings of the spleen in generalized mastocytosis (GM) is available and no comprehensive review of the literature on this subject has been published.

METHODS

The authors reviewed their records to study the macroscopic and microscopic features of the spleen in 53 patients; the authors also studied these features in 135 patients reported in the literature. Thus, a total of 188 patients with GM were studied.

RESULTS

Splenomegaly was noted in 72% of the patients, including 71% of the patients from the authors' files and 73% of the patients reported in the literature. The spleen weight, recorded in 39 of the patients, ranged from 160 g to 2300 g; in 29 (80%) patients the spleen weighed more than 500 g and in 4 (10%) patients, more than 2000 g. However, mast cell (MC) infiltration of the spleen was recorded in only 65 (34%) patients (patients from authors' records, 39%; patients reported in literature, 32%). The following combinations were extremely rare: splenomegaly without evidence of MC infiltration (n = 1); and histologic evidence of MC infiltration in the absence of splenomegaly (n = 2). The histologic findings of the spleen could be assessed in nine of the patients from the authors' files, eight of whom had MC infiltration. In four patients, infiltration was diffuse and confined mainly to the red pulp; in the other four patients, it was more focal and involved mainly the white pulp. Spleen plasmacytosis was found in eight patients, eosinophilia in five, hemosiderosis in seven, and fibrosis in six. Concurrent acute nonlymphoblastic leukemia was diagnosed in four patients, none of whom had the skin lesions of urticaria pigmentosa.

CONCLUSIONS

The authors' findings show that (1) splenomegaly is a common finding in GM and often is pronounced; (2) MC infiltration probably is the most important factor in the pathogenesis of splenomegaly in this disease; and (3) two different patterns of MC infiltration (diffuse and focal) can be identified in GM.