Cushing syndrome-associated adrenal cortical adenoma
Wednesday 4 April 2012
Cushing syndrome-associated adrenocortical adenoma
JRC:18775 : Adrenal cortical adenoma, left, with Cushing’s syndrome (F 43 y/o)
Definition: Tumors associated with Cushing syndrome are typically unilateral and present as sharply circumscribed masses that usually weigh less than 60g and measure 3 to 4c m in average diameter.
Tumors weighing more than 100g should be examined with particular care to rule out malignancy.
On cross section, adenomas vary from yellow to brown, and occasional examples of heavily pigmented (black) adenomas have been reported.
Microscopically, adenomas have pushing borders with a pseudocapsule derived from compression of the adjacent cortex or expansion of the adrenal capsule.
They are most often composed of small nests, cords, or alveolar arrangements of vacuolated (clear) cells that most closely resemble those of the normal fasciculata.
Generally, adenoma cells are somewhat larger than normal cortical cells.
Variable numbers of compact-type cells are also evident.
Black adenomas are composed exclusively of lipochrome-rich compact cells.
Foci of spindle cell growth may be evident in somecases, and
occasional adenomas may exhibit considerable fibrosis.
The nuclear-to-cytoplasmic ratio is generally low, although a few single cells and small cell groups may have enlarged hyperchromatic nuclei.
Typically, the nuclei are vesicular with small, distinct nucleoli. Mitotic activity is rare in adenomas.
Numerous naked nuclei in a background of granular to foamy material may be prominent.
On ultrastructural examination, adenoma cells most closely resemble the cells of the normal fasciculata or reticularis.
The cytoplasm typically contains abundant smooth endoplasmic reticulum and variable numbers of lipid droplets.
The mitochondria are round to ovoid with a predominance of tubulovesicular or exclusively vesicular cristae
Lamelliform cristae may also be present.
Foci of myelolipomatous change or calcification may be seen, particularly in larger adenomas.
The cortex adjacent to functional adenomas and in the contralateral adrenal is typically atrophic, with cortical cells that have a clear or vacuolatedcytoplasm.
The atrophy, however, does not involve the glomerulosa.
X chromosome in activation analyses have shown that some adenomas are clonal, whereas others are polyclonal.
Monoclonal adenomas are larger than polyclonal lesions and have a higher prevalence of nuclear pleomorphism.
This heterogeneity may reflect different pathogenetic mechanisms or different stages of a common multistep process
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