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
- Adrenlolipomas 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)