Definition
A tumour composed of both mature fat and haemopoietic components.
Myelolipomas occur in adults. There is a slight female preponderance. They are not associated with haematolymphoid neoplasms.
Myelolipoma most commonly occurs in the adrenal, but has also been reported at other sites, including the mediastinum. IN the adrenal, they may present as a mass, with abdominal pain or as an acute abdomen following rupture and haemorrhage of the tumour.
Myelolipomas are often incidental radiological findings. The presence of mature fat allows a radiological diagnosis to be made.
Within the tumour, there is trilineage haemopoiesis. Cellularity is widely variable from area to area within a tumour. The myeloid to erythroid ratio of 3 to 4:1 is similar to that of normal bone marrow but the number of megakaryocytes may be raised. Variable numbers of plasma cell, lymphocytes or eosinophils may be present. The background shows increased reticulin deposition compared to normal marrow. Rarely, there may be mature bone formation.
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stains blasts, small vessels and any vascular sinuses |
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CD42b |
stains megakaryocytes |
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stains variable numbers of mast cells |
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Non-random inactivation of the X chromosome in women shows that both the lipomatous and the haemopoietic elements are neoplastic.
Extramedullary haemopoiesis
Myeloid sarcoma / extramedullary sclerosing myeloid tumour: shows dysplasia and increased numbers of blasts.
This page last revised 23.7.2006.
©SMUHT/PW Bishop