Utility of Pit-1 Immunostaining in Distinguishing Pituitary Adenomas of Primitive Differentiation from Null Cell Adenomas

Elevated risk of recurrence and retreatment for silent pituitary adenomas

PURPOSE

Pituitary adenomas are the most common tumor of the pituitary gland and comprise nearly 15% of all intracranial masses. These tumors are stratified into functional or silent categories based on their pattern of hormone expression and secretion. Preliminary evidence supports differential clinical outcomes between some functional pituitary adenoma (FPA) subtypes and silent pituitary adenoma (SPA) subtypes.

METHODS

We collected and analyzed the medical records of all patients undergoing resection of SPAs or FPAs from a single high-volume neurosurgeon between 2007 and 2018 at Brigham and Women's Hospital. Descriptive statistics and the Mantel-Cox log-rank test were used to identify differences in outcomes between these cohorts, and multivariate logistic regression was used to identify predictors of radiographic recurrence for SPAs.

RESULTS

Our cohort included 88 SPAs and 200 FPAs. The majority of patients in both cohorts were female (48.9% of SPAs and 63.5% of FPAs). SPAs were larger in median diameter than FPAs (2.1 cm vs. 1.2 cm, p < 0.001). The most frequent subtypes of SPA were gonadotrophs (55.7%) and corticotrophs (30.7%). Gross total resection (GTR) was achieved in 70.1% of SPA resections and 86.0% of FPA resections (p < 0.001). SPAs had a higher likelihood of recurring (hazard ratio [HR] 3.2, 95% confidence interval [95%CI] 1.6-7.2) and a higher likelihood of requiring retreatment for recurrence (HR 2.5; 95%CI 1.0-6.1). Subset analyses revealed that recurrence and retreatment were more both likely for subtotally resected SPAs than subtotally resected FPAs, but this pattern was not observed in SPAs and FPAs after GTR. Among SPAs, recurrence was associated with STR (odds ratio [OR] 9.3; 95%CI 1.4-64.0) and younger age (OR 0.92 per year; 95%CI 0.88-0.98) in multivariable analysis. Of SPAs that recurred, 12 of 19 (63.2%) were retreated with repeat surgery (n = 11) or radiosurgery (n = 1), while the remainder were observed (n = 7).There were similar rates of recurrence across different SPA subtypes.

CONCLUSION

Patients undergoing resection of SPAs should be closely monitored for disease recurrence through more frequent clinical follow-up and diagnostic imaging than other adenomas, particularly among patients with STR and younger patients. Several patients can be observed after radiographic recurrence, and the decision to retreat should be individualized. Longitudinal clinical follow-up of SPAs, including an assessment of symptoms, endocrine function, and imaging remains critical.

Transcription Factor Immunohistochemistry in the Classification of Pituitary Neuroendocrine Tumor/Adenoma: Proposal in a Limited-Resource Setting

CONTEXT.—

Pituitary neuroendocrine tumors/adenomas are common intracranial tumors that require accurate subtyping because each tumor differs in its biologic behavior and response to treatment. Pituitary-specific transcription factors allow for improved lineage identification and diagnosis of newly introduced variants.

OBJECTIVE.—

To assess the usefulness of transcription factors and design a limited panel of immunostains for classification of pituitary neuroendocrine tumors/adenoma.

DESIGN.—

A total of 356 tumors were classified as per expression of pituitary hormones and transcription factors T-box family member TBX19 (TPIT), pituitary-specific POU-class homeodomain (PIT1), and steroidogenic factor-1 (SF-1). The resultant classification was correlated with patients' clinical and biochemical features. The performance and relevance of individual immunostains were analyzed.

RESULTS.—

Reclassification of 34.8% (124 of 356) of pituitary neuroendocrine tumors/adenoma was done after application of transcription factors. The highest agreement with final diagnosis was seen using a combination of hormone and transcription factors. SF-1 had higher sensitivity, specificity, and predictive value compared with follicle-stimulating hormone and luteinizing hormone. On the other hand, TPIT and PIT1 had similar performance and Allred scores compared with their respective hormones.

CONCLUSIONS.—

SF-1 and PIT1 should be included in the routine panel for guiding the classification. PIT1 positivity needs to be followed by hormone immunohistochemistry, especially in nonfunctional cases. TPIT and adrenocorticotropin can be used interchangeably as per availability of the lab.

The clinical presentation of PIT1 positive pituitary neuroendocrine tumor immunonegative for growth hormone, prolactin, and thyroid stimulating hormone with analysis of clinical and immunostaining dissociation

BACKGROUND

PIT1 is a pituitary transcription factor that is associated with either growth hormone (GH), prolactin (PRL), or thyroid-stimulating hormone (TSH) production. However, PIT1-positive pituitary neuroendocrine tumors (PitNETs) are occasionally immunonegative for GH, PRL, and TSH. This paper describes the clinical presentation of PIT1 positive however immunonegative PitNETs.

METHODS

We conducted a retrospective analysis, identifying 228 PIT1-positive PitNET patients between 2017 and 2022. Out of these, ten (4%) tested negative for GH, PRL, and TSH. Functioning PitNETs were defined as those causing hormonal excess symptoms or hormonal overproduction.

RESULTS

As for 10 patients immunonegative for all three hormones however PIT1-positive, the mean ( ± standard deviation) age was 46 ± 13 years with 70% women. Six patients exhibited signs of excess GH or PRL, and three had visual problems. Additionally, one patient had secondary hypothyroidism and adrenal insufficiency resulting from the mass effect. All tumors were macroadenoma, with a median volume of 2.1 cm3 (range, 0.8-17.5 cm3). Gross total resection was attained in six patients by trans-sphenoidal surgery. Postoperatively, eight patients experienced clinical improvement: three in vision, two in amenorrhea, two in headache, and one in acromegaly symptoms. Biochemical improvement was observed in six patients, with all experiencing remission in hormonal excess and one showing improvement in secondary hypothyroidism. Stereotactic radiosurgery was performed in three patients.

CONCLUSIONS

Patients with functioning PitNETs may exhibit PIT1 staining without GH, PRL, or TSH staining. Hormonally active tumors exist in this patient population; therefore, close endocrine follow-up is necessary despite the lack of staining for GH, PRL, and TSH.

Immunohistochemical Analyses of Mammalian Target of Rapamycin (mTOR) Expression in Pituitary Neuroendocrine Tumors (PitNETs): mTOR as a Therapeutic Target for Functional PitNETs

Current therapeutic modalities for pituitary neuroendocrine tumors (PitNETs) include medication, surgery, and radiotherapy. Some patients have tumors that are refractory to current modalities. Therefore, novel treatment options are needed for patients with intractable diseases. Consequently, we examined the pathological data of PitNETs to study medical therapies. We retrospectively studied 120 patients with histologically diagnosed PitNETs. We used the data for the histopathological examination of hormones, such as growth hormone (GH), prolactin (PRL), adrenocorticotropic hormone, thyroid stimulating hormone, luteinizing hormone, follicle-stimulating hormone, and α-subunit, together with the immunohistochemical studies of the phospho-mammalian target of rapamycin (mTOR), cytokeratin (CAM5.2), somatostatin receptor (SSTR) type 2 and 5, Pit-1 (POU1F1/GHF-1), steroidogenic factor-1 (SF-1), and Tpit. GH-, PRL-, and SSTR5-immunopositive PitNETs had significantly higher percentage of mTOR-positivity, compared with GH-, PRL-, and SSTR5-immunonegative Pit NETs. Our results show that activation of the AKT/phosphatidylinositol-3-kinase pathway, including mTOR activation, might be related the development of PitNETs, especially GH- and PRL-producing PitNETs. Thus, mTOR is a potential target for treating functional PitNETs.

Differences in invasiveness and recurrence rate among nonfunctioning pituitary neuroendocrine tumors depending on tumor subtype

PURPOSE

To clarify the invasiveness to surrounding structures and recurrence rate of each subtype of nonfunctioning pituitary neuroendocrine tumor (Pit-NETs) according to the WHO 2022 classification.

METHODS

This retrospective study utilized data from 292 patients with nonfunctioning Pit-NETs treated with initial transsphenoidal surgery. Recurrence was evaluated on 113 patients who were available for a magnetic resonance imaging follow-up ≥ 60 months. All tumors were assessed by immunohistochemical staining for Pit-1, T-PIT, and GATA3. Invasiveness to surrounding structures was evaluated based on intraoperative findings.

RESULTS

Cavernous sinus invasion was found in 47.5% of null cell tumors, 50.0% of Pit-1 lineage tumors, 31.8% of corticotroph tumors, and 18.3% of gonadotroph tumors. Dura mater defects in the floor of sellar turcica, indicating dural invasion, were found in 44.3% of null cell tumors, 36.4% of corticotroph tumors, 16.7% of Pit-1 lineage tumors, and 17.3% of gonadotroph tumors. In logistic regression analysis, Pit-1 (OR 5.90, 95% CI 1.71-20.4, P = 0.0050) and null tumors (OR 4.14, 95% CI 1.86-9.23, P = 0.0005) were associated with cavernous sinus invasion. Recurrence was found in 8 (4.9%) patients, but without significant differences between tumor subtypes. The presence of cavernous sinus invasion was correlated with recurrence (HR = 1.95, 95% CI 1.10-3.46, P = 0.0227).

CONCLUSION

Among nonfunctioning Pit-NETs, Pit-1 lineage tumors tend to invade the cavernous sinus, corticotroph tumors may produce dura mater defects, and null cell tumors tend to cause both. Pit-NETs with cavernous sinus invasion require a careful attention to recurrence.

Clinical features and therapeutic outcomes of GH/TSH cosecreting pituitary adenomas: experience of a single pituitary center

Background

Growth hormone (GH)/thyroid stimulating hormone (TSH) cosecreting pituitary adenoma (PA) is an exceedingly rare kind of bihormonal pituitary neuroendocrine tumors (PitNETs). Its clinical characteristics have rarely been reported.

Objectives

This study aimed to summarize the clinical characteristics and experience of diagnosis and treatment among patients with mixed GH/TSH PAs from a single center.

Methods

We retrospectively reviewed GH/TSH cosecreting PAs from 2063 patients diagnosed with GH-secreting PAs admitted to Peking Union Medical College Hospital between January 1st, 2010, and August 30th, 2022, to investigate the clinical characteristics, hormone detection, imaging findings, treatment patterns and outcomes of follow-up. We further compared these mixed adenomas with age- and sex-matched cases of GH mono-secreting PAs (GHPAs). The data of the included subjects were collected using electronic records from the hospital's information system.

Results

Based on the inclusion and exclusion criteria, 21 GH/TSH cosecreting PAs were included. The average age of symptom onset was 41.6 ± 14.9 years old, and delayed diagnosis occurred in 57.1% (12/21) of patients. Thyrotoxicosis was the most common complaint (10/21, 47.6%). The median inhibition rates of GH and TSH in octreotide suppression tests were 79.1% [68.8%, 82.0%] and 94.7% [88.2%, 97.0%], respectively. All these mixed PAs were macroadenomas, and 23.8% (5/21) of them were giant adenomas. Comprehensive treatment strategies comprised of two or more therapy methods were applied in 66.7% (14/21) of patients. Complete remission of both GH and TSH was accomplished in one-third of cases. In the comparison with the matched GHPA subjects, the mixed GH/TSH group presented with a higher maximum diameter of the tumor (24.0 [15.0, 36.0] mm vs. 14.7 [10.8, 23.0] mm, P = 0.005), a greater incidence of cavernous sinus invasion (57.1% vs. 23.8%, P = 0.009) and a greater difficulty of long-term remission (28.6% vs. 71.4%, P <0.001). In addition, higher occurrence rates of arrhythmia (28.6% vs. 2.4%, P = 0.004), heart enlargement (33.3% vs. 4.8%, P = 0.005) and osteopenia/osteoporosis (33.3% vs. 2.4%, P = 0.001) were observed in the mixed PA group.

Conclusion

There are great challenges in the treatment and management of GH/TSH cosecreting PA. Early diagnosis, multidisciplinary therapy and careful follow-up are required to improve the prognosis of this bihormonal PA.

A challenging TSH/GH co-secreting pituitary adenoma with concomitant thyroid cancer; a case report and literature review

BACKGROUND

Thyroid stimulating hormone (TSH) secreting pituitary adenoma (TSHoma) with coexisting thyroid cancer is extremely rare, and proper treatment of both diseases may pose a unique clinical challenge. When TSHoma has plurihormonality, particularly involving the co-secretion of growth hormone (GH), management can be more complicated. Herein, we present a difficult-to-manage case of papillary thyroid cancer with an incurable TSH/GH-secreting pituitary adenoma.

CASE PRESENTATION

A 59-year-old man was referred to our hospital due to memory impairment and inappropriate TSH level. Sella magnetic resonance imaging revealed a huge pituitary mass extending to the suprasellar area. Clinical diagnosis of TSH/GH co-secreting pituitary adenoma was made based on elevated free T4, total T3, serum α-subunit, insulin-like growth factor-1 levels and non-suppressible GH levels after oral glucose loading. Rectal cancer and multifocal papillary thyroid microcarcinoma (PTMC) were diagnosed during initial screening for internal malignancy; lower anterior resection was performed and close observation was planned for PTMC. Long-acting octreotide therapy was commenced, which resulted in a dramatic reduction in TSHoma size and facilitated control of hormonal excess. Total thyroidectomy and radioactive iodine (RAI) therapy were needed during follow up due to the growth of PTMC. After the surgery, the pituitary adenoma represented resistance to somatostatin analogue therapy and the tumor size gradually increased despite the addition of dopamine agonist therapy. Furthermore, TSH suppressive therapy with levothyroxine was impossible and an adequate TSH level for RAI therapy was unmountable. Late debulking pituitary surgery was ineffective, and the patient gradually deteriorated and lost to follow up.

CONCLUSION

We report the first aggravated case of TSH/GH co-secreting pituitary tumor after total thyroidectomy for concomitant multifocal PTMC. Deferring of thyroid surgery until the TSHoma is well controlled may be the optimal therapeutic strategy in patients with TSHoma and coexistent thyroid cancer; ablative thyroid surgery may result in catastrophic pituitary tumor growth.

Expression of additional transcription factors is of prognostic value for aggressive behavior of pituitary adenomas

OBJECTIVE

According to the latest WHO classification of tumors of endocrine organs in 2017, plurihormonal adenomas are subclassified by their transcription factor (TF) expression. In the group of plurihormonal adenomas with unusual immunohistochemical combinations (PAWUC), the authors identified a large fraction of adenomas expressing TFs for gonadotroph adenoma (TFGA) cells in addition to other TFs. The aim of this study was to compare clinicopathological parameters of PAWUC with TFGA expression to gonadotroph adenomas that only express TFGA.

METHODS

This retrospective single-center series comprises 73 patients with TFGA-positive pituitary adenomas (SF1, GATA3, estrogen receptor α): 22 PAWUC with TFGA (TFGA-plus group) and 51 with TFGA expression only (TFGA-only group). Patient characteristics, outcome parameters, rate of invasiveness (assessed by direct endoscopic inspection), and MIB1 and MGMT status were compared between groups.

RESULTS

Patients in the TFGA-plus group were significantly younger than patients in the TFGA-only group (age 46 vs 56 years, respectively; p = 0.007). In the TFGA-only group, pituitary adenomas were significantly larger (diameter 25 vs 18.3 mm, p = 0.002). Intraoperatively, signs of invasiveness were significantly more common in the TFGA-plus group than in the TFGA-only group (50% vs 16%, p = 0.002). Gross-total resection was significantly lower in the nonfunctioning TFGA-plus group than in the TFGA-only group (44% vs 86%, p = 0.004). MIB1 and MGMT status showed no significant difference between groups.

CONCLUSIONS

These data suggest a more aggressive behavior of TFGA-positive adenomas if an additional TF is expressed within the tumor cells. Shorter radiographic surveillance and earlier consideration for retreatment should be recommended in these adenoma types.

Proposal of a clinically relevant working classification of pituitary neuroendocrine tumors based on pituitary transcription factors

The immunohistochemistry (IHC) characterization of pituitary transcription factors (PTFs) PIT1, TPIT, and SF1, which enable the identification of three different adenohypophyseal cell lines, has been incorporated into the latest classification system of the World Health Organization (WHO) for pituitary adenomas. This change overturns the concept of the adenoma as solely a hormone producer and classifies these tumors based on their cell lineage. The aim of the study was to provide a diagnostic algorithm, based on IHC expression of hypophyseal hormones with potential use in diagnostic practice, contributing to an improved classification of pituitary adenomas. Our sample included 146 pituitary adenomas previously classified based on hormonal subtypes by IHC (former 2004 WHO criteria) and re-evaluated after the IHC quantification of PIT1, TPIT, and SF1 expression, under WHO 2017 recommendations. We assessed the correlation between expression of PTFs and the classification as per hormonal IHC and correlated clinicopathological profiles based on PTFs. The IHC study of PTFs allowed reclassification of 82% of tumors that were negative for all pituitary hormones, with 21 positive cases for SF1 (reclassified as gonadotroph tumors), 1 positive case for TPIT (reclassified as a corticotroph tumor), and 4 positive cases for PIT1. Using SF1 enabled detection of a substantial portion of gonadotroph tumors, reducing the estimated prevalence of null cell tumors to less than 5%, and identification of plurihormonal pituitary neuroendocrine tumors with PIT1-SF1 coexpression and hormone-negative PIT1s, a group in which we did not observe differences in the clinical behavior compared with the rest of the tumors of the same cell lineage.Our results suggest that applying a diagnostic algorithm based on the study of PTFs could contribute to improving the classification of pituitary adenomas. By adding TPIT assessment, we propose a two-step algorithm, with hypophyseal hormones being used in a selective modality, depending on initial results.

Molecular Biology of Pituitary Adenomas

Pituitary adenomas are benign tumors, but still cause significant morbidity and in some cases increases in mortality. Surgical resection is not without risks, and approximately 40% of adenomas are incompletely resected. Medical therapies such as dopamine agonists, somatostatin analogues, and growth hormone antagonists are associated with numerous side effects. Understanding the molecular biology of pituitary adenomas may yield new therapeutic approaches. Additional studies are needed to help determine which genes or pathways are "drivers" of tumorigenesis and should be therapeutic targets. Further studies may also enable pituitary adenoma stratification to tailor treatment approaches.

Recurrent non-functioning pituitary adenomas: a review on the new pathological classification, management guidelines and treatment options

At least 50% of surgically resected non-functioning pituitary adenomas (NFPA) recur. Either early or late adjuvant radiotherapy is highly efficacious in controlling recurrent NFPA but associates potentially burdensome complications like hypopituitarism, vascular complications or secondary neoplasm. Reoperation is indicated in bulky tumor rests compressing the optic pathway. To date, no standardized medical therapy is available for recurrent NFPA although cabergoline and temozolomide show promising results. Guidelines on the management of recurrent NFPAs are now available. The new 2017 WHO pituitary tumor classification, based on immunohistochemistry and transcription factor assessment, identifies a group of aggressive NFPA variants that may benefit from earlier adjuvant therapy. Nevertheless, NFPA patients exhibit a reduced overall life expectancy largely due to hypopituitarism and treatment-related morbidity. The management of recurrent NFPA benefits from a multidisciplinary teamwork of surgeons, endocrinologists, radiation oncologists, ophthalmologists, pathologists and neuro-radiologists in order to provide individualized therapy and anticipate deterioration.

Malignant transformation in non-functioning pituitary adenomas (pituitary carcinoma)

Non-functioning pituitary carcinomas (NFPC) are defined as tumours of adenophyseal origin with craniospinal or systemic dissemination, with the absence of a hormonal hypersecretion syndrome. These are a histologically heterogenous group of tumours, comprising gonadotroph, null cell, "silent" tumours of corticotroph, somatotroph or lactotroph cell lineages as well as plurihormonal Pit-1 tumours. NFPC are exceedingly rare, and hence few cases have been described. This review has identified 38 patients with NFPC reported in the literature. Recurrent invasive non-functioning pituitary adenomas (NFPA) were observed in a majority of patients. Various factors have been identified as markers of the potential for aggressive behaviour, including rapid tumour growth, growth after radiotherapy, gain or shift of hormone secretion and raised proliferative markers. Typically, there is a latency of several years from the original presentation with an NFPA to identification of metastases and only 5 cases reported with rapidly progressive malignant disease within 1 month of presentation. Therapeutic options include debulking surgery, radiation therapy and chemotherapy with temozolomide recommended as first line systemic treatment. Although long-term survivors are described, prognosis remains generally very poor (median survival 8 months). Improvements in molecular tumour profiling may assist in predicting tumour behaviour, guide therapeutic choices and identify novel therapies.

Management of non-functioning pituitary adenomas: surgery

Non-functional pituitary adenomas (NFPAs) are benign tumors of the pituitary gland that do not over-secrete hormonal products, therefore, they are generally detected through symptoms of mass effect, including headache, vision loss, or hypopituitarism. There are multiple pathological subtypes of NFPAs, such as null cell adenomas, silent gonadotrophs, silent somatotrophs, silent corticotrophs, and silent subtype 3, all of which can be classified based on immunohistochemical studies and electron microscopy. Despite these numerous pathological subtypes, surgical resection remains the first-line treatment for NFPAs. Diagnosis is best made using high resolution MRI brain with and without gadolinium contrast, which is also helpful in determining the extent of invasion of the tumor and recognizing necessary sinonasal anatomy prior to surgery. Additional pre-operative work-up should include full laboratory endocrine evaluation with replacement of hormone deficiencies, and ideally, full neuro-ophthalmologic exam. Although transcranial surgical approaches to the pituitary gland can be performed, the most common approach used is the transnasal transsphenoidal approach with endoscopic or microscopic visualization. This approach avoids retraction of the brain and cranial nerves during tumor removal. Surgery for symptoms caused by mass effect, including headaches and visual loss, are successfully treated with surgical resection, resulting in improvement in pre-operative symptoms as high as 90% in some reports. Although the risk of complications is low, major and minor events, such as permanent hypopituitarism, persistent CSF leak, and carotid artery injury can occur at rates ranging from zero to about 9%.