Refractory pituitary adenoma: a novel classification for pituitary tumors

// Congxin Dai 1, * , Ming Feng 1, * , Xiaohai Liu 1 , Sihai Ma 1 , Bowen Sun 1 , Xinjie Bao 1 , Yong Yao 1 , Kan Deng 1 , Yu Wang 1 , Bing Xing 1 , Wei Lian 1 , Dingrong Zhong 2 , Wenbin Ma 1 , Renzhi Wang 1 1 Department of Neurosurgery, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, China 2 Department of Pathology, Peking Union Medical College Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100730, China * These authors have contributed equally to this work Correspondence to: Renzhi Wang, email: Wangrz@126.com Keywords: pituitary adenomas, refractory, resistance, recurrence, aggressive Received: June 16, 2016     Accepted: October 03, 2016     Published: November 10, 2016 ABSTRACT Pituitary adenomas are classified as typical or atypical, invasive or noninvasive, and aggressive or nonaggressive based on pathological features, radiological findings, and clinical behavior. Only pituitary tumors with cerebrospinal and/or systemic metastasis are considered malignant carcinomas. However, some pituitary adenomas with high Ki-67 indexes exhibit aggressive behaviors, such as rapid growth, early and frequent recurrence, and resistance to conventional treatment, even in the absence of metastasis. Novel terminology is needed to define these tumors. Here, we propose the use of the term “refractory pituitary adenoma” to define malignant pituitary tumors exhibiting 1) a high Ki-67 index and rapid growth, 2) early and high frequency of recurrence, 3) resistance to conventional treatments and/or salvage treatment with temozolomide (TMZ), 4) poor prognosis, 5) and a lack of cerebrospinal or systemic metastases. To illustrate the utility of this refractory pituitary adenoma classification and the difficulty in managing disease in these patients, we examined twelve clinical cases. Correctly identifying refractory pituitary adenomas is crucial for improving patient prognoses. Early identification might encourage the early use of aggressive therapeutic strategies to prevent or delay recurrence.