Report Describes Ectopic Cushing’s Syndrome Caused by Thymic Tumor

Tumors in the thymus that produce too much of the adrenocorticotropic hormone (ACTH) may be the cause of ectopic Cushing’s syndrome, a case report shows. ACTH staining may be useful to confirm ACTH production in suspicious tumors, researchers said.

The study, “Ectopic Cushing’s syndrome due to adrenocorticotropic hormone secreting atypical thymic carcinoid tumor,” was published in the Northern Clinics of Istanbul.

Cushing’s syndrome caused by excess ACTH is usually due to tumors in the pituitary gland that produce too much of this hormone. In some cases, however, the disease may be caused by tumors elsewhere in the body that have the ability to produce ACTH.

Ectopic ACTH secretion is mostly seen in lung tumors, but in rare cases, tumors in the thymus may also produce this hormone.

Researchers at the Usak University Faculty of Medicine, Turkey  presented the case of a 50-year-old man who developed ectopic Cushing’s syndrome due to a thymic tumor.

The patient was admitted to a hospital emergency room after complaining of fatigue and weight loss (17.6 pounds in the past two years). He had a history of hypothyroidism — when the thyroid does not secrete enough hormones — and hypertension (elevated blood pressure), two conditions for which he was given medication.

Based on the initial physical and symptom evaluation, the clinical team suspected Cushing’s syndrome. Blood analysis revealed high levels of cortisol and ACTH hormones, and cortisol did not decrease after dexamethasone treatment.

While this was suggestive of an ACTH-dependent Cushing’s syndrome, the pituitary was normal and producing normal amounts of ACTH, leading the researchers to suspect ectopic Cushing’s syndrome.

The physicians conducted a computed tomography (CT) scan of the thorax and found a tumor in the thymus. Biopsy of the mass showed it was positive for ACTH.

Because the tumor showed signs of local invasion, the patient was considered unfit for surgery, and treated with chemotherapy and radiotherapy.

Overall, researchers showed that ectopic Cushing’s syndrome can be caused by tumors in the thymus, which are often occult and difficult to determine as the source of ACTH.

“In this case, we used ACTH staining in thymic tissue to confirm ACTH secretion from these tissues, and positive staining was detected,” they said, concluding that “in difficult cases, ACTH staining can be helpful to confirm the presence of ACTH secretion in tumor tissues.”