Endocrine Abstracts

Pituitary adenomas constitute the third most common intracranial neoplasm. Adenoma cells either express no hormone (null cell adenoma) or hormones of different cell lineage. About 1% of pituitary adenomas shows a plurihormonal expression pattern, which may either be attributed to one cell lineage or rarely to different cell lineages. In addition, the development of separate pituitary adenomas may be observed in 0.5–1.5% of surgical specimens and in up to 10% of autopsy cases. These lesions are termed synchronous multiple pituitary neuroendocrine tumors (PitNETs) and are traditionally known as difficult to be detected at preoperative imaging investigation. Synchronous multiple PitNETs clinical manifestations depend on the histological subtypes. Specifically, null cell adenomas are invasive at the time of presentation and have an aggressive clinical course with short progression-free survival. We present a case of a 45-years old woman in which, following the diagnostic investigations for a suspected Guillain-Barrè syndrome, a 13 mm pituitary lesion was found on brain MRI images. On T2-weighted images, the lesion was described as iso-hypointense in the peripheral edge and hyperintense in the central portion with mild compressive effect on the pituitary stalk and optic chiasm. Despite the absence of clinical acromegalic features, the blood tests showed an increased baseline GH and IGF-1 levels (4.9 ng/ml and 401 ng/ml respectively) and the lack of GH suppression during OGTT test (GH nadir 3.9 ng/ml) confirming the diagnosis of acromegaly. Transsphenoidal surgery was performed with a regular post-operative course, with disease remission confirmed by biochemical and radiological investigation at one- and three-months follow-up. At histology, a synchronous multiple PitNETs were found, consisting of a PIT-1 lineage and a null cell adenomas. The former was a mixed somatotroph-lactotroph PitNET with a low mitotic and proliferative index (<3 mitoses for 10 HPF, Ki67<3%). On the other hand, the latter was characterized by spindle cells, negative for all pituitary hormones and transcription factors (TTF-1, T-PIT, SF1, PIT1 and GATA3) with focal p53 overexpression and a high proliferative index (Ki67 5-6%). Given the ambiguous histological nature of this component, the case was discussed collectively, deposing for possible aggressive behavior of the null cell adenoma. In conclusion, this is a rare and incidentally discovered case of a synchronous multiple PitNETs, in which the absence of acromegalic features and the histological characterization may suggest an aggressive and rapidly growing neoplasm, that require careful clinical-radiological post-operative follow-up.