Technetium-99m methoxyisobutylisonitrile localizes an ectopic ACTH-producing tumour: case report and review of the literature

Abstract

Extensive investigation including whole-body examinations with computed tomography and magnetic resonance imaging did not detect the suspected ectopic ACTH-producing tumour in a patient with advanced Cushing's syndrome and hypokalemic alkalosis. Gamma camera examination with technetium-99m methoxyisobutylisonitrile (MIBI) depicted the tumour, which was localized in the anterior neck and mediastinum. This was later verified by surgery. 99mTc-MIBI is normally used for myocardial scintigraphy. Its accumulation is unspecific and merely reflects metabolic activity. Despite this, the present case shows that examination with this agent can provide important information with regard to tumour localization in a given situation, thereby serving as a complement to other imaging modalities. The current literature on 99mTc-MIBI for tumour diagnosis is reviewed.

Cervical Paraganglioma Mimicking a Parathyroid Adenoma on Tc-99m Sestamibi Scintigraphy

“…1,2 Although this imaging technique has a high sensitivity for locating hyperfunctioning parathyroid glands, false-positive uptake in various other cervical tumors is also known. [3][4][5][6] Paragangliomas or glomus tumors are most commonly located in the head and neck and stem from parasympathetic ganglia. In up to 10% of patients, these tumors may be diagnosed incidentally during imaging performed for multiple reasons.…”

A Case of Cushing`s Syndrome in ACTH - secreting Mediastinal Paraganglioma

“…It can be used to localize lesions not seen on other scans 10 ) . The 99m technetium-methoxyisobutylisonitrile (MIBI) scan is also helpful to detect ectopic ACTH-producing tumors undiagnosed with CT and MRI 11 ) .…”

Ectopic ACTH Syndrome due to Thymic Carcinoid Tumor in a Girl

“…In previous reports, these tumors were undetected on plain chest X-ray for such a long period that they commonly resulted in unnecessary adrenal surgery and eventual tumor dissemination 9 . Theoretically, a nuclear medicine scan is an ideal technique for early detection of this kind of tumor 14 . Jacobsson et al reported a patient with an ectopic ACTH-producing tumor, undetected by wholebody CT and MRI, but localized by a 99mTc-MIBI scan 14 .…”