Thymus hyperplasia after resolution of hypercortisolism in ACTH-dependent Cushing’s syndrome: the importance of thymic vein catheterization

Thymic hyperplasia has been described after the resolution of hypercortisolism from several etiologies, causing great diagnostic dilemmas. We describe a case where the catheterization of the thymic vein was essential for the differential diagnosis of a thymic enlargement in an adrenalectomized patient with ACTH-dependent Cushing’s syndrome. The patient was a 48-year-old female with clinical and laboratorial data suggesting Cushing’s disease. She underwent a transsphenoidal surgery with no tumor visualization and no remission of the syndrome. Histopathological studies disclosed a normal pituitary. She underwent a bilateral adrenalectomy and 8 months later a chest CT showed an increase of left thymic lobe, which was previously non-existent. After a negative 111In-pentetreotide scintigraphy, the patient underwent simultaneous and bilateral catheterism of the petrosus sinuses and catheterization of the thymic and inominate veins and no ACTH gradient was shown among the sites of collection. She did not undergo thoracotomy and a follow-up was established. During the evolution, there was a spontaneous regression of the thymic lesion 38 months after the diagnosis. The ACTH gradient during the catheterization of thymic vein was essential for the differential diagnosis of the thymic enlargement tumor after hypercortisolism resolution in ACTH-dependent Cushing’s syndrome, especially in this case, where the ACTH source was occult, thus avoiding an invasive surgical procedure for a benign entity with spontaneous resolution.

Enlargement of the Thymus following Chemotherapy for Non-Seminomatous Testicular Cancer

The thickness of the largest thymic lobe at computed tomography (CT) was measured retrospectively in 21 relapse free patients who had undergone chemotherapy for non-seminomatous testicular cancer. CT was performed at initial staging, at completion of chemotherapy and 3 to 12 months later. Enlargement of the thymus occurred in 7 patients, one of whom had a reduced thymic size at the first two examinations after chemotherapy. A temporary reduction was detected in another patient in whom the original thymic size was regained 19 months after start of chemotherapy. The mean age of the group with thymic enlargement was 21 years compared with a mean age of 28 years in the group with no increased size. The age difference between the two groups was significant (p<0.05, Mann-Whitney U test). To reduce the number of explorative thoracotomies the frequent occurrence of thymic enlargement after chemotherapy for non-seminomatous testicular cancer should be kept in mind.