Adrenolipoma pathophysiology
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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1] Associate Editor(s)-in-Chief: Ahmad Al Maradni, M.D. [2]
Overview
On gross pathology, central congested red to brown lesion, with thin cortical rim is a characteristic finding of adrenolipoma. On microscopic histopathological analysis, variable amounts of adipocytes and hematopietic cells are characteristic findings of adrenolipoma.
Pathogenesis
- Myelolipomas are usually less than 4 cm in size occasionally measuring more than 10 cm in size.
- Extra-adrenal sites for myelolipomas include the retroperitoneum, thorax, and pelvis.
- Usually unilateral however they can also involve both adrenals.
- One hypothesis suggests that stimuli, such as necrosis, inflammation, infection, or stress could cause adrenocortical cell metaplasia
- If chronically present these stimulants lead to the development of neoplasms.
This hypothesis is supported by the increased incidence of the lesion in the advanced years of life.
- On gross pathologic examination, a cut section of a myelolipoma has a variegated appearance consisting of bright yellow areas of fat, dark red areas of hematopoietic myeloid tissue, and areas with intermixed red and yellow components.
- On histopathologic examination, myelolipomas are predominantly composed of fatty areas with interspersed hematopoietic tissue components.
- These fatty elements and hematopoietic areas may be clearly separated, or they are often intermixed.
- Tissue analysis often reveals a variable amalgamation of myeloid and erythroid cells, megakaryocytes, and occasionally lymphocytes.
- In an isolated adrenal myelolipoma, a peripheral rim of normal adrenal cortical tissue can be commonly identified distinctly from the mass.
- Rarely the myelolipomas can contain osteoid tissue in addition to the myeloid tissue.
The hemorrhagic areas may be partly replaced by fibrotic tissue or may undergo calcification
Gross Pathology
Macroscopic examination demonstrates:[1]
Central congested red to brown lesion, with thin cortical rim. Large lesions may contain hemorrhage or infarction.
Microscopic Pathology
Histological examination demonstrates:[1]
- Variable amounts of mature adipocytes (with distended lipid vacuoles) similar to bone marrow
- Variable amounts of hematopoietic cells (including cells from myeloid, erythroid and megakaryocytic cells lines)