Pulmonary myelolipoma containing osseous tissue: An unexpected finding at autopsy.

Pulmonary myelolipoma is a very rare benign tumor composed of mature adipose tissue and hematopoietic elements such as erythroid, myeloid and megakaryocytic. It usually represents accidental finding during autopsy or chest imaging, since most cases are asymptomatic. Larger masses can lead to hemorrhage, chest pain and chest organ compression. We present a case of incidental finding of pulmonary myelolipoma during the autopsy of an 83- year old woman who died of abdominal aortic rupture. In the right lower lung lobe, solitary, well-circumscribed yellow-brown nodule which was 3 cm in its longest diameter was found. Pathohistological analysis revealed tumor composed of mature adipose tissue and hematopoietic cells (myeloid cells, megakaryocytes, erythroid cells) with fragments of mature bone tissue. Differential diagnosis of pulmonary myelolipoma includes lipoma, liposarcoma, hamartoma, phlebangioma, teratoma and extramedullary hematopoiesis. In majority of cases, tumor removal is not necessary, however, larger lesions should be surgically removed. No cases of malignant transformation or recurrence have so far been reported in the literature.