SAT-105 - A Rare Case of Prolactin-Secreting Pituitary Carcinoma with Spinal Metastasis

Pituitary carcinoma is an exceptionally rare entity, comprising 0.1-0.2% of pituitary tumors. Diagnosis requires documented craniospinal or systemic metastases, as histopathology alone cannot reliably distinguish carcinoma from aggressive adenoma. Most cases initially present as invasive macroadenomas that later demonstrate malignant behavior through resistance to surgery, medical therapy, and radiotherapy. Management remains challenging, with reported survival after metastasis ranging from 1.5 to 11.3 years.

We report a 74-year-old woman with an aggressive, dopamine agonist-resistant invasive macroprolactinoma. Diagnosed in 2002 following galactorrhea, she was treated with escalating cabergoline doses with persistent hyperprolactinemia (Prolactin 4978 ng/ml) and tumor progression. Despite high dose cabergoline (max of 9 mg/week), she developed cavernous sinus invasion and visual compromise, prompting transsphenoidal surgery (TSS) in 2017, followed by repeat TSS in 2018. Pathology consistently demonstrated Prolactin- and GH-positive Pituitary NET (neuroendocrine tumor) with low proliferative index. Continued progression led to fractionated radiotherapy (2018), resulting in partial regression and biochemical improvement, complicated by central hypothyroidism. Residual disease remained stable for several years. Due to further progression and ineligibility for additional radiation, temozolomide was initiated in 2022, achieving radiographic stability and prolactin reduction before discontinuation in 2024 due to suspected neuropathy. Prolactin levels started rising again in 2025 with progression of sellar disease. DOTATATE PET/CT in September 2025 showed uptake in the sellar region without evidence of any distant metastases. CARIS molecular profile did not show any targetable mutations. In November 2025, she underwent a third TSS for progressive sellar disease. Pathology showed lactotroph pituitary NET with higher proliferative index (Ki67 10%). In December 2025, she presented with acute neurological decline; imaging revealed a C5-C6 intradural mass with spinal cord compression. Surgical resection confirmed metastatic lactotroph pituitary NET, establishing the diagnosis of pituitary carcinoma.

This case illustrates the diagnostic and therapeutic complexity of prolactin-secreting pituitary NET with spinal metastasis. Resistance to standard therapies necessitates multimodal and multidisciplinary management. Temozolomide remains first-line systemic therapy, though responses are variable. Emerging treatments, including immune checkpoint inhibitors and peptide receptor radionuclide therapy, may offer benefit in refractory disease. This report adds to the limited literature on metastatic pituitary NET and highlights the need for improved predictive biomarkers and novel therapeutic strategies.

*Unless otherwise noted, all abstracts presented at ENDO must not be released to the press or the public until the date and time of presentation. For oral presentations, the abstracts are embargoed until the session begins. The Endocrine Society reserves the right to lift the embargo on specific abstracts that are selected for promotion prior to or during ENDO.*