Current opinion on the diagnosis and management of non-functioning pituitary adenomas

Using digital PCR to investigate the prevalence of KRAS variants in pituitary tumours

Pituitary tumours (PT) are formed in the pituitary gland, a small gland situated at the base of the brain. These tumours can be categorized according to their histological origin and hormone production. In surgical series, non-functioning PT are the commonest subtype, followed by functioning somatotroph and corticotroph tumours. Different somatic alterations have been implicated in the pathogenesis of these tumours and the objective of our study was to expand our previous new finding of KRAS pathogenic genetic variants in pituitary tumours. We conducted a digital polymerase chain reaction (PCR) analysis on formalin-fixed paraffin-embedded tissue blocks belonging to 189 patients. The results showed that, from the 184 pituitary tumours with good quality samples, 13 tumours (7.1%) presented mutant KRAS. The median age of the mutated group was 47 years old (range 19-77) and most patients with mutant KRAS tumours were from the female gender (61.5%, 8/13) and non-functioning subtype. For the first-time, mutant KRAS in corticotroph and somatotroph tumours were detected, and the variants showed low allele frequencies. In conclusion, we demonstrated that pituitary tumours might have mutant KRAS, and these data were not previously described probably due to lack of sensitivity of previous technologies. By identifying these variants, even at minimal levels, we open doors to a deeper understanding of the tumour microenvironment, clonal evolution and potential therapeutic targets.

Somatostatin receptors in pituitary somatotroph adenomas as predictors of response to somatostatin receptor ligands: A pathologist's perspective

There are five subtypes of somatostatin receptors (SST1-5), which are expressed in several types of solid neoplasms, neuroendocrine tumors, and pituitary adenomas. Most commonly, SST2 and SST5, are of interest regarding diagnostic, treatment, and prognostic purposes. In this article the basic biological characteristics of SST are briefly reviewed, and focus given to the immunohistochemical evaluation of SST2 and SST5 in growth hormone (GH)-secreting pituitary tumors, and their quantification as predictors of response to treatment with somatostatin receptor ligands (SRL), the mainstay of the pharmacological therapy available for these tumors. Although many different scoring systems for SST2 immunohistochemistry showing correlation with SRL response have been reported, among which the immunoreactivity score (IRS) has been the most consistently used, a universally validated immunohistochemical technique and scoring scheme is lacking. Efforts should be made on collaborative multicenter studies aiming at validating homogeneous immunostaining protocols and a scoring system for SST2 and SST5 expression, to help clinicians to define the optimal therapeutic strategy for the patients with somatotroph tumors.

Update on Current Evidence for the Diagnosis and Management of Nonfunctioning Pituitary Neuroendocrine Tumors

Pituitary neuroendocrine tumors (PitNETs) are the third most frequently diagnosed intracranial tumors, with nonfunctioning PitNETs (nfPitNETs) accounting for 30% of all pituitary tumors and representing the most common type of macroPitNETs. NfPitNETs are usually benign tumors with no evidence of hormone oversecretion except for hyperprolactinemia secondary to pituitary stalk compression. Due to this, they do not typically present with clinical syndromes like acromegaly, Cushing's disease or hyperthyroidism and instead are identified incidentally on imaging or from symptoms of mass effects (headache, vision changes, apoplexy). With the lack of effective medical interventions, first-line treatment is transsphenoidal surgical resection, however, nfPitNETs often have supra- or parasellar extension, and total resection of the tumor is often not possible, resulting in residual tumor regrowth or reoccurrence. While functional PitNETs can be easily followed for recurrence using hormonal biomarkers, there is no similar parameter to predict recurrence in nfPitNETs, hence delaying early recognition and timely management. Therefore, there is a need to identify prognostic biomarkers that can be used for patient surveillance and as therapeutic targets. This review focuses on summarizing the current evidence on nfPitNETs, with a special focus on potential new biomarkers and therapeutics.

Current and Emerging Medical Therapies in Pituitary Tumors

Pituitary tumors (PT) represent in, the majority of cases, benign tumors for which surgical treatment still remains, except for prolactin-secreting PT, the first-line therapeutic option. Nonetheless, the role played by medical therapies for the management of such tumors, before or after surgery, has evolved considerably, due in part to the recent development of well-tolerated and highly efficient molecules. In this review, our aim was to present a state-of-the-art of the current medical therapies used in the field of PT and the benefits and caveats for each of them, and further specify their positioning in the therapeutic algorithm of each phenotype. Finally, we discuss the future of PT medical therapies, based on the most recent studies published in this field.