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UNUSUAL PRIMARY MALIGNANT RETICULOSIS OF THE BONE MARROW

An unusual case of primary reticulosis of the bone marrow in a 67‐year‐old female has been described. Pathological‐anatomical characteristics of the present case are as follows; 1) Primary non‐destructive proliferation of neoplastic reticulum cells or their variants, confined to the systemic bone marrow. Metastatic foci were noted in several areas where extramedullary hematopoiesis occurred. 2) Cytologically, neoplastic cells resemble atypical plasmacytic cells. No active phagocytosis was noted in neoplastic cells. 3) Histologically a significant increase in reticulin flbers was observed closely associated with proliferating cells. 4) Electron‐microscopically these cells showed developed endoplasmic reticula but were distinguishable from myeloma cells by their irregular cytoplasmic border, which became frequently obscure, and by the presence of a desmosome‐like structure. 5) These cells showed a negative immunofluorescent reaction to all types of human immunoglobulin classes. The morphological characteristics of these cells distinguished the disorder from poorly differentiated myelomatosis.