Systemic mast cell disease: a clinical and hematopathologic study of 26 cases.

Systemic mast cells disease (SMCD) is an uncommon disorder that constitutes approximately 10% of all mastocytoses. Diagnosis requires a substantial degree of clinical suspicion, which may not be present if characteristic skin lesions of urticaria pigmentosa are not observed. Lack of well-defined histopathologic features for the disease have delayed or prevented the diagnosis of SMCD. An initial diagnosis of "myeloproliferative disorder," chronic granulocytic leukemia, or myelofibrosis is frequently made. Study of the clinical and pathologic features of 26 cases of SMCD indicated that affected patients are generally middle aged and may have had urticaria pigmentosa for many years. Gastrointestinal symptoms are common, and splenomegaly and hepatomegaly along with radiographic evidence of generalized bone disease are usually noted. Hematologic factors are highly variable. Characteristic histopathologic features of SMCD are described for bone marrow, lymph nodes, liver, and spleen. The authors consider tissue fixation and staining methods to help identify mast cell lesions.