Fig.20.35 ).Bothglandsareenlarged,eithersubtlyormarkedly,eachweighingupto30g.Theadrenalcortexisdiffuselythickenedandvariablynodular,althoughthelatterisnotaspronouncedasincasesofACTH-independentnodularhyperplasia.Theyellowcolorofdiffuselyhyperplasticglandsderivesfromthepresenceoflipid-richcells,whichappearvacuolatedunderthemicroscope.
Inprimarycorticalhyperplasia,thecortexisreplacedalmostentirelybymacronodulesor1-to3-mmdarklypigmentedmicronodules(
Fig.20.36 ).Thepigmentisbelievedtobelipofuscin,awear-and-tearpigment(Chapter2).
Functionaladenomasorcarcinomasoftheadrenalcortexarenotmorphologicallydistinctfromnonfunctioningadrenalneoplasms(discussedlater).Boththebenignandmalignantlesionsaremorecommoninwomenintheirthirtiestofifties.Adrenocorticaladenomasareyellowtumorssurroundedbythinorwell-developedcapsules,andmostweighlessthan30g(
Fig.20.37A ).Onmicroscopicexamination,theyarecomposedofcellssimilartothoseencounteredinthenormalzonafasciculata(see
Fig.20.37B ).ThecarcinomasassociatedwithCushingsyndrome,bycontrast,tendtobelargerthantheadenomas.
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Fig.20.36(A)Primarypigmentednodularadrenocorticalhyperplasiashowingprominentpigmentednodulesintheadrenalgland.(B)Onhistologicexamination,thenodulesarecomposedofcellscontaininglipofuscinpigment,seenintherightpartofthefield.(Photographs courtesy of Dr. Aidan Carney, Department of Medicine, Mayo Clinic, Rochester, Minnesota.)
Thesetumorsarenonencapsulatedmassesfrequentlyexceeding200to300ginweight,havingalloftheanaplasticcharacteristicsofcancer,asdetailedlater.Withfunctioningtumors,bothbenignandmalignant,theadjacentadrenalcortexandthatofthecontralateraladrenalglandareatrophic,asaresultofsuppressionofendogenousACTHbyhighcortisollevels.
The signs and symptoms of Cushing syndrome represent an exaggeration of the known actions of glucocorticoids. Cushing syndrome usually develops gradually and, like many other endocrine abnormalities, may be quite subtle in its early stages. A major exception to this insidious onset is Cushing syndrome associated with small-cell carcinomas of the lung, when the rapid course of the underlying disease precludes development of many of the characteristic features. Early manifestations of Cushing syndrome include hypertension and weight gain. With time, the more characteristic centripetal redistribution of adipose tissue becomes apparent, with resultant truncal obesity, “moon facies,” and accumulation of fat in the posterior neck and back (“buffalo hump”). Hypercortisolism causes selective atrophy of fast-twitch (type II) myofibers, with resultant decreased muscle mass and proximal limb weakness. Glucocorticoids induce gluconeogenesis and inhibit the uptake of glucose by cells, resulting in secondary diabetes with its attendant hyperglycemia, glucosuria, and polydipsia. The catabolic effects of insulin resistance on proteins cause loss of collagen. Thus, the skin is thin, fragile, and easily bruised; cutaneous striae are particularly common in the abdominal area (