Clinicopathological variations in cushing's syndrome.

In the majority of cases, Cushing's disease is the result of a small basophilic corticotroph microadenoma with an average size of less than 5 mm. Transsphenoidal microsurgery can cure patients with Cushing's disease; however, selective removal of the lesion requires precise preoperative localization. In this article, we present the pathological findings and clinical outcomes of four patients who underwent inferior petrosal sinus sampling (IPSS) for ACTH, pituitary imaging and subsequent transsphenoidal surgery for the diagnosis and treatment of Cushing's disease. All patients fulfilled accepted biochemical criteria for the diagnosis of ACTH-dependent Cushing's syndrome. Histological examination revealed a basophilic corticotroph adenoma in two patients. In one other patient, only Crooke's hyalinization was found; however, the patient achieved a complete clinical and biochemical remission following a hemihypophysectomy based on IPSS findings. Thus, a microadenoma was assumed or proven in three patients, of whom two were cured by surgery alone. In the third patient, cortisol excess persisted following transsphenoidal surgery because of a coexistent functioning adrenal adenoma. The fourth patient developed recurrent nodular corticotroph hyperplasia following a 17-yr remission. The second transsphenoidal procedure failed to ameliorate cortisol excess, necessitating a subsequent bilateral adrenalectomy. IPSS accurately localized the site of the lesion in all four cases. Although magnetic resonance imaging (MRI) identified a distinct lesion in three cases, two of these represented false positives (a cyst in one case and a prolactinoma in the other), whereas in only one did MRI correctly match the site of the lesion. In each case, conflicting test results and/or difficult management decisions posed a challenge. Thus, successful resolution of disease requires a multidisciplinary approach to validate clinical, biochemical, and radiographic data based on morphologic findings.