SAT-477 Pituitary Carcinoma Arising from a Macroprolactinoma

Background: Pituitary carcinomas make up 0.2% of all pituitary carcinomas and remain a challenging diagnosis to make with few effective treatment options. Clinical Case: A 73-year old man with a past medical history of a pan-hypopituitarism secondary to a prolactinoma who had undergone multiple resections in 1969 and 1992 presented to the emergency room with worsening headache and progressive vision loss for two weeks. He was doing well until symptoms recurred in 2017 and he subsequently underwent another resection in July of 2018 at an outside hospital. Five weeks post-resection his MRI showed rapid progression of his disease and at this time he presented to our facility. On presentation, his prolactin level was 41,890 ng/mL while on cabergoline 0.25mg three times weekly. His other laboratory results were consistent with pan-hypopituitarism and he was on treatment with hydrocortisone and levothyroxine. Initially, cabergoline was increased to 0.5mg three times weekly but prolactin levels remained persistently high. Repeat imaging showed a local invasive 5.6 x 4.8 x 4.0 cm left anterior skull base mass. The patient then underwent another resection in August of 2018. Pathology was significant for strong nuclear immunoreactivity of p53, a Ki-67 index greater than 20%, high mitotic activity with 16/10hpf, and strong prolactin reactivity. Temozolomide therapy alongside radiation therapy was recommended. A systematic review by Almalki et al., showed around a 60% response in patient with aggressive pituitary tumors with Temozolomide.(1) Unfortunately, the patient developed meningitis post-operatively and has required repeated re-admissions for altered mental status. He has now started radiation therapy, but Temozolomide therapy remains on hold. Conclusion: Prolactinomas are usually well-controlled by dopamine agonists. Refractory forms are rare and can rapidly progress making treatment very challenging. An initially large size mass with invasion, associated systemic metastasis or recurrence should raise suspicion for malignancy. Any delays in the initiation of therapy should be avoided, which can include surgery, external beam radiotherapy, radiosurgery, various chemotherapeutic approaches such as temozolomide, an alkylating agent, which is currently only approved for glioblastoma multiforme and refractory anaplastic astrocytoma. (1)Almalki MH, Aljoaib NN, Alotaibi MJ, Aldabas BS, Wahedi TS, Ahmad MM, et al. Temozolomide therapy for resistant prolactin-secreting pituitary adenomas and carcinomas: a systematic review. Hormones. 2017;16(2):139–49.