An Institutional Experience of Tumor Progression to Pituitary Carcinoma in a 15-Year Cohort of 1055 Consecutive Pituitary Neuroendocrine Tumors Omalkhaire M. Alshaikh 1,2 & Sylvia L. Asa 3,4 & Ozgur Mete 3,4 & Shereen Ezzat 1,5 # Springer Science+Business Media, LLC, part of Springer Nature 2019 Abstract Pituitary carcinoma is a rare disease, defined by the presence of cerebrospinal or distant metastasis of a pituitary neuroendocrine tumor (PitNET). To review our institutional experience of pituitary carcinoma, we searched the database of the UHN Endocrine Oncology Site group and the University Health Network pathology laboratory information system from 2001 to 2016. Among 1055 PitNETs from 1169 transsphenoidal resections, we identified 4 cases of pituitary carcinoma, indicating that pituitary carcinoma represents around 0.4% of PitNETs. All four patients were women. The age at initial presentation ranged from 23 to 54 years. Two patients had Cushing disease with corticotroph tumors; one was initially a densely granulated corticotroph tumor that evolved to become sparsely granulated, while the other was a Crooke cell tumor. One patient had a functioning sparsely granulated lactotroph tumor and one had a clinically silent poorly differentiated PIT1 lineage tumor. Apart from a relatively high Ki67 labeling index (≥ 10%) in three tumors, there were no cytomorphologic features at the time of initial presentation that could predict subsequent metastatic behavior. The time from diagnosis of the pituitary neuroendocrine tumor to the diagnosis of malignancy was 3 to 14 years. Therapies included somatostatin analogs, external beam radiotherapy, chemotherapies including capecitabine/temozolomide, everolimus, sunitinib, bevacizumab, and peptide receptor radionuclide therapy (PRRT). One patient died of disease 18 years after initial diagnosis, underscoring the protracted course of this ultimately fatal neuroendocrine malignancy. Keywords Pituitary carcinoma . Pituitary neuroendocrine tumor . Metastasis . Ki67 Introduction Pituitary carcinoma is a rare disease, defined by the presence of cerebrospinal or distant metastasis of an adenohypophysial tumor [1, 2]. The vast majority of patients who receive this diagnosis present initially with a pituitary neuroendocrine tumor (PitNET) [3] that has no distinctive features to suggest metastatic potential. The ability to distinguish these carcinomas from other aggressive PitNETs remains a challenge [ 4]. Only a small number of cases of pituitary carcinoma have been reported in the literature [5–45]. The majority are corticotroph tumors with Cushing disease [ 42, 43], but tumors of all of the various adenohypophysial cell types have been reported to be malignant. We reviewed our institutional experience with pitui- tary carcinoma since the publication of a previous case [26]. Materials and Methods To review our institutional experience of pituitary carcinoma, we searched the database of the UHN Endocrine Oncology This study was presented in abstract form at Endocrine Society as BAn Institutional Experience of Pituitary Carcinomas in a 15 year Cohort of 1055 Consecutive Pituitary Neuroendocrine Tumors (PitNETs)^ (Presentation Number: MON-583; Date of Presentation: March 19, 2018). * Shereen Ezzat shereen.ezzat@utoronto.ca 1 Department of Medicine, Princess Margaret Cancer Centre, University Health Network and University of Toronto, Toronto, Ontario, Canada 2 Department of Medicine, Al Imam Mohammad Ibn Saud Islamic University, Riyadh, Saudi Arabia 3 Department of Pathology, University Health Network, Toronto, Canada 4 Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada 5 Princess Margaret Cancer Centre, University Health Network, 610 University Avenue, Room 7-327, Toronto, Ontario M5G 2M9, Canada Endocrine Pathology https://doi.org/10.1007/s12022-019-9568-5