| Paper # 095 | Spanish version
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| Paper # 095 | Spanish version
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Andréa Rodrigues Cordovil Pires, Luciana Wernersbach Pinto.
[Title] [Materials and Methods] [Results] [Pictures] [Discussion] [Bibliography]
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Agnogenic myeloid metaplasia (AMM) is a chronic myeloproliferative disease characterized by a pluripotential hematopoietic stem cell clonal proliferation, myelofibrosis and extramedullary hematopoiesis. Its origin is still obscure, but there are some reports of chemical (benzene) and radiation (atomic bomb) injury preceeding AMM (1, 10). AMM has been divided into two evolutive phases, based in bone marrow histology:
Cellular phase AMM can evolve into osteosclerotic phase and this latter into leukemic transformation in 6% of the cases, with acute myelocytic, myelomonocytic, megakaryoblastic and even lymphoblastic differentiation (5). Extramedullary hematopoiesis is an important associated finding in AMM. The most affected sites are liver and spleen, but it can be seen in virtually any organ - adrenal gland, lung, kidney, skin, lymphnode, bowels, central nervous system and endometrium, besides producing pleural, pericardial or peritoneal effusions (6, 12, 20). Myelofibrosis is another important feature in this disease. It is now creditable that neoplastic megakaryocytes secrete fibroblastic growth factors that stimulate fibroblast proliferation and collagen synthesis. Due to bone marrow sinusoids distortion caused by fibrosis, immature hematopoietic cells reach circulation and lodge in other organs, where extramedullary hematopoiesis will develop (13). Probably, soluble growth factors (GF) produced by neoplastic cells and fibroblasts stimulate macrophages and mantain extramedullary hematopoiesis. One of these GF is CSF-1 (monocyte/macrophage colony stimulating factor - M-CSF). It was found that in chronic myeloproliferative diseases (CMP), particularly AMM, patients have high serum levels of CSF-1, correlating with the degree of extramedullary hematopoiesis (myeloid metaplasia). It suggests that M-CSF can control, directly or by association with other growth factors, the amount and distribution of extramedullary hematopoiesis (8). The presence of this GF in circulating blood could explain macrophage expansion and activation in CMP and maybe, the association of AMM with sarcoidosis in two literature cases, thought to be due to immunological response to neoplastic antigens (17). The differential diagnosis, specially in cellular phase, is sometimes very difficult, and include the other CMP, namely polycytemia vera, essential thrombocythemia and chronic myeloid leukemia.
Myelolipoma is a rare benign neoplasm of unknown origin, usually affecting adrenal glands (2, 4, 15, 18), but it can be seen in other sites, as retroperitoneum (16, 19, 21). There are little more than a hundred cases of myelolipoma reported in literature, some associated with other diseases or conditions, as hypertention, obesity, diabetes mellitus (2, 7), malignancy (3), renal cell carcinoma (9, 19) and Von Hippel-Lindau syndrome (21). Generally myelolipomas are assiptomatic and found accidentally during surgery, autopsy or radiologic procedures. They are composed of typical adipocytes and hematopoietic cells of the three lineages in all development stages. It can show mixoid change in stroma, areas of calcification and hemorrhage, but no atypical cells (14, 16). The differential diagnosis include lipossarcomas, mixoid malignant fibrous histiocytomas and extramedullary hematopoietic tumors.
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