The amount of fatty component is variable, ranging from only a few small regions in an otherwise mostly soft tissue density mass (10%) to masses made up of roughly equal components of fat and soft tissue (50%) or almost completely composed of fatty tissue (40%) 9. The mass is usually relatively well circumscribed, however masses that are mostly fat may be difficult to separate from surrounding retroperitoneal fat. The typical adrenal myelolipoma appears as an adrenal lesion with fat-containing components. The CT appearance is usually characteristic. Fat within a myelolipoma can slow the ultrasound waves, resulting in the artifactual appearance of a discontinuous diaphragm 21. Areas of hemorrhage appear hypoechoic on ultrasonography 19. Usually is seen as a heterogeneous mass of mixed hyper- and hypoechoic components with the former primarily resulting from fatty portions. Radiographic features UltrasoundĮxact sonographic appearances are varied depending on individual tumor components 1. The lesions can infrequently contain bone 10 or show partial replacement by hemorrhage or fibrosis. The fatty component is often the predominant feature and therefore the most characteristic feature on imaging. hematopoietic cells (including cells from myeloid, erythroid and megakaryocytic cell lines).mature adipocytes (with distended lipid vacuoles) similar to bone marrow.Histological examination demonstrates variable amounts of: rarely it can present in extra-adrenal locations 16.Conn syndrome (primary hyperaldosteronism).congenital adrenal hyperplasia (21-hydroxylase deficiency).There may be a right-sided predilection 5.Īlthough the tumor itself is non-functioning there is a relatively high incidence (10%) of associated endocrine disorders 9: Larger lesions (typically over 4 cm in size) can present with an acute retroperitoneal hemorrhage, and still others (especially when very large) with vague mass-related symptoms 9. Most lesions are asymptomatic 6 and may be discovered incidentally when the region is imaged for other reasons (i.e. 10% of patients with adrenal myelolipoma have congenital adrenal hyperplasia 20.Myelolipomas are rare tumors of the adrenal glands with an estimated autopsy prevalence of 0.1-0.2%. They are usually identified in adults, either incidentally or if complicated by hemorrhage (see below).
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