Fourteen-year bridge to cure in occult ectopic ACTH syndrome: resection of a 3-mm pulmonary carcinoid.

Ectopic adrenocorticotropic hormone (ACTH) syndrome (EAS) often involves occult microtumors, making localization challenging. We report a 68-year-old woman with severe ACTH-dependent hypercortisolism in whom the primary tumor remained occult despite extensive imaging, including 68Ga-tetraazacyclododecanetetraacetic acid-D-Phe(1)-Tyr(3)-octreotide positron emission tomography/computed tomography. Based on a positive octreotide challenge test, she received long-acting release octreotide for over a decade, achieving sustained biochemical stability. In 2020, she developed breast cancer, with the tumor being ACTH-negative on immunohistochemistry. In 2023, during resection of pulmonary metastases of the breast cancer, a 3-mm nodule was incidentally discovered in the adjacent lung tissue. Through close interdisciplinary coordination, the nodule was removed and was confirmed as an ACTH- and somatostatin receptor (SSTR) 2-positive pulmonary carcinoid. Thereafter, the EAS resolved completely with prompt recovery of adrenal function. In this case, intensive medical stabilization in occult EAS probably served as a strategic "bridge to surgery." Importantly, long-term biochemical control using somatostatin analogs facilitated prompt recovery of the hypothalamic-pituitary-adrenal axis immediately after tumor resection. This may also have preserved SSTR2 expression, potentially by mitigating cortisol-induced receptor downregulation, facilitating its eventual localization. This report shows that meticulous multidisciplinary communication during unrelated surgical procedures is indispensable for identifying radiologically occult lesions.