Endocrine Abstracts

Introduction: Somatotroph pituitary adenomas (PAs) represent 10-15% of all resected PAs, exhibiting immunohistochemical (IHC) positivity for GH (growth hormone) and PIT-1 transcription factor (TF). The histopathological (HP) and IHC variability of each PA influences the phenotype, radiological features, and therapy response.

Materials and methods: The study included 33 patients with acromegaly, with men: women ratio of 17:16. The HP-IHC characteristics were correlated with the clinical, imaging and laboratory data. Tumour specimens were assessed for anterior pituitary hormones, PIT-1, TPIT and SF-1 TF, Ki-67 labelling index, vimentin and reticulin.

Results: Of all cases, 30 had GH hypersecretion, while 3 had GH and PRL co-secretion. The symptomatology at diagnosis was dominated by the increase in size of extremities, associated with facial changes. Regarding the complications, they were identified right from the diagnosis, almost 50% of patients being hypertensive. Over 90% were macroadenomas. The maximum tumour diameter at diagnosis was positively correlated with suprasellar extension (P 0.001), the latter being also correlated with tumour invasion (P<0.0001). The postoperative tumour size was positively correlated with the postoperative value of random GH (P 0.01), the postoperative control of the residual secretion having a negative correlation with the maximum initial diameter. Regarding the biochemical evaluation, a statistically significant correlation was observed between the initial diagnostic values of IGF-1 and nadir GH in OGTT (P 0.02), respectively random GH (P 0.01), correlation maintained postoperatively (P 0.004 and <0.001, respectively). Most PAs were acidophilic, all had a positive IHC expression for GH. As expected, 93.93% had positive expression for PIT-1. PAs with IHC expression positive exclusively for GH accounted for 36.36%, while 13 cases (39.39%) showed a positive expression also for PRL. The expression of the other adenohypophyseal hormones was 12.12% for TSH, 3.03% for ACTH, and 9.09% for LH, respectively. Four cases were plurihormonal PIT-1 positive PAs, all with positive expression for PIT-1. Four cases had unusual IHC hormonal combinations. A particular feature of these PAs was the positive expression of the transcription factor SF-1 in a fairly large number of patients (39.39%). Most had a Ki-67 value below 3%.

Conclusions: The IHC classification of PAs, as stated by the WHO 2017 classification criteria, associated with the radiological dimensions and extent influence disease control, and are, probably, the most accurate prognostic factors. The 4 plurihormonal PIT-1 positive PAs associated a good cell differentiation and strongly acidophilic tinctoriality, advocating for a well-differentiated, mature tumour variant.