Discussion. Paper # 095

Paper # 095

Adrenal Myelolipoma in a patient with Agnogenic Myeloid Metaplasia.

Andréa Rodrigues Cordovil Pires, Luciana Wernersbach Pinto.

[Title] [Introduction] [Materials and Methods] [Results] [Pictures] [Bibliography]

DISCUSSION

Agnogenic myeloid metaplasia is not a well stablished malignat neoplasia - it is known to be a clonal proliferation of a pluripotent hematopoietic precursor cell still with commitment, differentiation and maturation capacities, but we still do not know exactly what causes extramedullary hematopoiesis. The same happens with myelolipoma. It's regarded to be a benign neoplasm of unknown origin, but there's no stablished data on its clonality or patients' growth factors status. Other unanswered questions are about its resemblance of normal hematopoietic bone marrow, the source of fat cells and the preference of adrenal gland location.

We figured out an explanation for the coexistance of these rare lesions in this patient: after a oncogenic stimulus (maybe chemical exposure during her work in a plastic factory for four years) she developed oncogenic transformation in a pluripotent stem cell that gave origin to AMM. As bone marrow became hypercellular and structurally abnormal due to fibrosis, some stem and precursor cells got to peripheral blood. Once they reached compatible microenvironments they stablished colonies in liver, spleen, lymphnodes and both adrenal glands. These colonies were supplied by soluble growth factors produced probably by megakaryocytes, fibroblasts and activated macrophages. One of the left adrenal colonies developed an aditional capacity, maybe to secrete local factors capable of stablish a microenvironment closer to bone marrow and transform fibroblasts or themselves into stromal cells - adipocytes and fibroblasts (4, 11). This new characteristic gave it growth advantages, so it grew, compressed adrenal cells and got restricted by its capsule. The same pathway (migration of a mutant pluripotent stem cell) could explain the occurrence by chance of myelolipoma in patients without other diseases. The other proposition is that the coexistance of these two rare neoplasms is only a coincidence.

Probably the ten day treatment with G-CSF had some effect in bone marrow myeloid hyperplasia, once the autopsy specimen was a little more cellular than the biopsy one. Once AMM is related to macrophage activation and sarcoid-like reactions, we can imagine if the leprosy compatibility diagnosis was a reflection of this activation and not a real infectious disease. It is a difficult question, once leprosy has high incidence in our state and the formation of granulomas is not a very common finding in AMM. The patient died due to severe pulmonary bacterial infection secondary to upper airways infection, one of the most common causes of death in AMM patients.

This is a interesting case of the coexistance of two rare neoplasms. We believe that they are possibly correlated. Maybe soluble growth factors secreted by neoplastic cells, activated fibroblasts or macrophages could have stimulated a hematopoietic stem cell to develop a hematopoietic microenvironment in adrenal gland. There are some questions that will only be answered after more studies on these entities.