Blood findings in 61 cases of generalized mastocytosis (GM) were evaluated. The cases were divided into two major variants: Systemic mastocytosis (SM; n = 34) with urticaria pigmentosa-like skin lesions, and malignant mastocytosis (MM; n = 27), without skin involvement. The following results were obtained: (1) Significant differences between MM and SM were found in the main haematological parameters (erythrocyte, platelet and leucocyte counts and haemoglobin level); normal values were found in 16 of the SM cases, but never in MM. (2) The main pathological findings were: in SM, anaemia (9/34) and leucocytosis (5/34); and in MM, leucocytosis (19/27), monocytosis (14/27), eosinophilia (12/27), bicytopenia (12/27, mostly anaemia with thrombocytopenia), basophilia (10/27) and isolated anaemia (7/27). (3) The major finding was a significant difference between MM and SM in the incidence of myeloproliferative disorders (MPD), myelodysplasia and mast cell leukaemia (MCL): these disorders occurred in 23 (92%) MM patients, but only in two (6%) SM patients (P less than 0.001). The four instances of MCL and two of myelodysplasia all occurred with MM. Of the 19 cases of MPD, six (SM, 1; MM, 5) were acute variants (acute myeloid and myelomonocytic leukaemias) and 13 (SM, 1; MM, 12) were chronic variants. No case of malignant lymphoma was noted. (4) The blood picture in 10 of 13 chronic MPD cases represented an atypical chronic myeloid leukaemia for which the preliminary descriptive term 'mastocytosis-associated MPD' is proposed. (5) A survey of 103 published cases (SM, 77; MM, 26) yielded similar findings, including a high incidence of MPD and MCL in MM. These findings add further weight to the argument for recognizing SM and MM as two separate entities.

The findings suggest that both decidual LGLs and a subset of decidual T cells are activated and possibly play a role in the control of trophoblast growth and placental development.

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. Cancer 1992; 70:459–468.

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