MON-050 Ectopic Acromegaly in a Young Female due to a Lung Neuroendocrine Tumor

Abstract Disclosure: C. Pérez-Castañeda: None. C.G. Abreu-Rosario: None. C. Ramírez-Rentería: None. M. Mercado-Atri: None. A. Pérez-Verdin: None. L.I. Pozos: None. G. González-Villaseñor: None. A. Pozos-Ochoa: None. J. Medina-Andrade: None. Background: Ectopic acromegaly is a rare condition mostly caused by GHRH hormone secretion from a neuroendocrine tumor. The clinical features of this disease are indistinguishable from those of acromegaly caused by a pituitary adenoma. However, the absence of a pituitary tumor in a patient with acromegaly features suggests an ectopic origin. Diagnosis can be challenging because its main symptoms often overlap with those of other conditions. Clinical Case: This is the case of a 33 year old female with a palpable breast nodule accompanied by cough, weight loss, night sweats, palpitations, and hot flashes. A breast biopsy was performed, revealing findings consistent with poorly differentiated carcinoma. Subsequent CT imaging demonstrated a mass within the right upper pulmonary lobe and multiple lesions at the breast, liver, bone, and thyroid. She presented to the endocrinology clinic for a thyroid nodule biopsy. During this evaluation, examination revealed classic acromegalic features. Biochemical analysis confirmed the diagnosis of active acromegaly, with an IGF-1 index of 1.8 (Basal GH 10.7 ug/L ;IGF-1 515.9 ng/ml,GH nadir 5.43 ug/l) . Subsequently, a pituitary MRI was performed on two separate occasions, demonstrating pituitary enlargement without any focal lesions. The rest of pituitary hormones were within normal ranges. Evaluation of GHRH revealed levels of 220 pg/ml (normal: 5-18 pg/ml). Immunohistochemical staining was positive for chromogranin A, with a Ki-67 index of 2-3%, supporting a neuroendocrine origin. Tc-99m bone scintigraphy confirmed metastatic lesions. An octreotide scintigraphy with 111-In Pentetreotide showed increased uptake in the breast, lung and bone. Following diagnosis, the patient received monthly Octreotide 20 mg. One year later, she received capecitabine and temozolomide treatment. After three years of stable response to treatment, her dosing interval was reduced to four weeks due to biochemically and clinically active acromegaly. Surgical debulking was not performed due to high operative risk associated with the tumor's proximity to the aorta. The patient, now two years post-treatment, remains under regular outpatient surveillance with stable disease per RECIST 1.1 criteria, indicating no significant structural changes, and an IGF-1 index of 1.2. Conclusion: This case highlights the diagnostic challenges associated with ectopic acromegaly, which underscores the importance of heightened clinical suspicion to avoid misdiagnosis, particularly in young patients with potentially increased survivals. Dissemination of such cases within the medical literature may aid clinicians in recognizing the constellation of signs and symptoms suggestive of this disease. Prompt referral to a specialized medical center with a multidisciplinary team is essential for optimal outcomes. Presentation: Monday, July 14, 2025