Clinico-pathological and molecular characteristics of pediatric-juvenile pituitary neuroendocrine tumors (PitNETs): A mono-institutional series

: Our purpose was to provide a clinical-pathological overview, evaluate the prognostic value of Ki-67 and p53 in pediatric-juvenile pituitary neuroendocrine tumors (PitNETs) and explore the incidence of somatic variants in SF3B1 in pediatric-juvenile lactotroph PitNET. We present a clinical, morphological, immunohistochemical, and molecular study of 30 patients aged 8 - 20 years (16 females, 53%; 14 males, 47%). Clinical data were available for 21 patients (70%). Nine patients (43%) had mass effect symptoms. Imaging was available for 25 cases (83%). 21 patients (84%) had macro-PitNET or giant PitNET. Most tumors were lactotroph PitNETs (22 cases, 73%). Nine patients out of 22 lactotroph PitNET (41%) were male. Ki-67 and p53 immunostaining were performed in 27 cases. 15 tumors (56%) were p53 positive and exhibited a high Ki-67 index. Of these, 12 tumors (80%) were macro-PitNETs or giant PitNETs. Eight tumors (30%) were p53 negative and had low Ki-67 index, with 5 of these classified as macro-PitNETs (100% of the cases for which this data was available). Genetic analysis of the recurrent SF3B1 c.1874G>A p.Arg625His was negative in all 15 tested tumors. In conclusion, pediatric-juvenile PitNETs are often large lesions causing mass effects in almost half of the cases. In our cohort, lactotroph PitNETs were the most frequent PitNETs and present without sex predilection. SF3B1 mutations, documented in a proportion of adult lactotroph PitNETs, were not observed in our cohort, potentially hinting at a different molecular background. Our results did not reveal any association between Ki-67 and p53 status and tumor size or invasiveness in pediatric-juvenile PitNETs.