Pituitary neuroendocrine tumors: a pitbull in medicine

SESSION TITLE: Disorders of the Mediastinum Case Report Posters 4 SESSION TYPE: Case Report Posters PRESENTED ON: 10/09/2023 02:10 pm - 02:55 pm INTRODUCTION: The differential diagnosis for a paratracheal mass is fairly broad and includes thymoma, lymphoma, germ cell tumors, and thyroid/parathyroid goiters or tumors. This case highlights endobronchial ultrasound with transbronchial needle aspiration (EBUS-TBNA) as a minimally invasive sampling technique which was critical in the prompt diagnosis of a very rare clinical entity. CASE PRESENTATION: A 31 year old female with a past medical history of atypical pituitary adenoma, acromegaly, and prior deep venous thrombosis presented to clinic for evaluation of a new paratracheal mass. Five years prior to presentation, she underwent trans-nasal trans-sphenoidal tumor resection and definitive radiotherapy for her pituitary adenoma with complete response. Routine surveillance laboratory testing revealed an elevated insulin like growth factor-1 (IGF-1) level of > 1000 ng/mL. An MRI head showed no changes in the pituitary which prompted a contrasted CT chest that revealed a well-circumscribed hypodensity in the left paratracheal region inferior to the thyroid measuring 4 x 3 cm. EBUS-TBNA of a station 2L lymph node and left paratracheal mass was performed. Pathology demonstrated small tumor cells with eosinophilic cytoplasm, round nuclei, and speckled chromatin. Immunostaining was positive for CAM 5.2, synaptophysin, PIT-1, GH, and was weakly positive for prolactin. Taken together, these findings were suggestive of a hormone secreting, metastatic pituitary neuroendocrine tumor. A staging PET-CT was ordered and the patient was referred to surgical oncology for resection of the mediastinal mass. DISCUSSION: Pituitary neuroendocrine tumors (PitNET) previously referred to as pituitary adenomas, are typically localized to the pituitary with a relatively benign clinical course. Occasionally, PitNETs invade local structures and very rarely, these tumors metastasize. The incidence of metastatic PitNET is approximately 0.1 to 0.2% of pituitary tumors and clinical presentation is highly variable depending on the functional status, location, and size of the metastatic lesion. Sites of pituitary tumor metastasis include the brain, spinal cord, leptomeninges, bone, liver, lymph nodes, ovary, heart, and lung. Interestingly, systemic spread of the disease is postulated to occur by way of venous circulation to the lungs. Nevertheless, pulmonary/mediastinal sites for the metastasis of PitNET are rarely seen. These tumors require effective coordination of multimodal therapies because of their aggressive behavior. Current therapies include surgical resection, adjuvant radiotherapy, and temozolomide as first line chemotherapy. CONCLUSIONS: While pituitary neuroendocrine tumors/adenomas account for 15% of intracranial tumors, metastatic PitNETs are exceedingly rare. A review from 2004 reported only 140 well-documented cases in the English literature. To our knowledge, this is the first case reported of a hormone secreting, PitNET with metastasis to the mediastinum. REFERENCE #1: Du Four S, Van Der Veken J, Duerinck J, et al. Pituitary carcinoma - case series and review of the literature. Front Endocrinol (Lausanne). 2022;13:968692. doi:10.3389/fendo.2022.968692 REFERENCE #2: Melmed S. Pituitary-Tumor Endocrinopathies. N Engl J Med. Mar 05 2020;382(10):937-950. doi:10.1056/NEJMra1810772 REFERENCE #3: Ragel BT, Couldwell WT. Pituitary carcinoma: A review of the literature. Neurosurgical Focus. 2004;16(4):1-9. doi:10.3171/foc.2004.16.4.8 DISCLOSURES: No relevant relationships by Brian Boer No relevant relationships by Jie Chen No relevant relationships by Andjela Drincic No relevant relationships by Catherine Joyce No relevant relationships by Ana Yuil