Surgical treatment of pituitary neuroendocrine tumors with coexisting intracranial lesions: A case series and review of the literature

Background

Pituitary neuroendocrine tumors (PitNETs) are a diverse group of benign neoplasms that account for a significant proportion of intracranial tumors (13%). The coexistence of PitNET with other intracranial lesions, such as meningiomas and intracranial aneurysms, has been constantly reported in the literature; yet, the pathophysiological mechanisms remain unknown, and the appropriate management is controversial. This study aims to describe the clinical characteristics, surgical treatment, and outcomes of patients with PitNET with coexisting intracranial lesions in a single healthcare center.

Methods

A retrospective analysis was conducted on 12 patients who underwent surgical treatment for PitNET and another intracranial lesion at our single tertiary referral center over 15 years from January 2008 to May 2023.

Results

Among these coexisting lesions, aneurysms were the most commonly found (41.67%), followed by meningiomas (33.33%). Surgical intervention for both lesions was performed in a single-stage procedure for most cases (75%), employing transcranial, endoscopic endonasal, and combined approaches. We found low preoperative Karnofsky Performance Scale scores in three patients, with significant differences in functional outcomes.

Conclusion

These findings contribute to the limited knowledge about PitNET coexisting with other intracranial lesions and emphasize the importance of patient-tailored, multidisciplinary management in these unusual scenarios.

Clinical Characteristics, Diagnosis, and Treatment of Thyroid Stimulating Hormone-Secreting Pituitary Neuroendocrine Tumor (TSH PitNET): A Single-Center Experience

Background

Thyroid-stimulating hormone (TSH)-secreting pituitary neuroendocrine tumor (TSH PitNET) is a rare subtype of Pit- NET. We investigated the comprehensive characteristics and outcomes of TSH PitNET cases from a single medical center. Also, we compared diagnostic methods to determine which showed superior sensitivity.

Methods

A total of 17 patients diagnosed with TSH PitNET after surgery between 2002 and 2022 in Samsung Medical Center was retrospectively reviewed. Data on comprehensive characteristics and treatment outcomes were collected. The sensitivities of diagnostic methods were compared.

Results

Seven were male (41%), and the median age at diagnosis was 42 years (range, 21 to 65); the median follow-up duration was 37.4 months. The most common (59%) initial presentation was hyperthyroidism-related symptoms. Hormonal co-secretion was present in four (23%) patients. Elevated serum alpha-subunit (α-SU) showed the greatest diagnostic sensitivity (91%), followed by blunted response at thyrotropin-releasing hormone (TRH) stimulation (80%) and elevated sex hormone binding globulin (63%). Fourteen (82%) patients had macroadenoma, and a specimen of one patient with heavy calcification was negative for TSH. Among 15 patients who were followed up for more than 6 months, 10 (67%) achieved hormonal and structural remission within 6 months postoperatively. A case of growth hormone (GH)/TSH/prolactin (PRL) co-secreting mixed gangliocytoma-pituitary adenoma (MGPA) was discovered.

Conclusion

The majority of the TSH PitNET cases was macroadenoma, and 23% showed hormone co-secretion. A rare case of GH/TSH/PRL co-secreting MGPA was discovered. Serum α-SU and TRH stimulation tests showed great diagnostic sensitivity. Careful consideration is needed in diagnosing TSH PitNET. Achieving remission requires complete tumor resection. In case of nonremission, radiotherapy or medical therapy can improve the long-term remission rate.

Different tumor growth pattern of clinically nonfunctioning pituitary neuroendocrine tumor according to sex and age: a longitudinal study

PURPOSE

Asymptomatic patients with clinically non-functional pituitary neuroendocrine tumors (CNF-PitNETs) are usually followed up. However, the natural course of CNF-PitNETs according to sex and age remains unclear. Therefore, this study assessed growth patterns of CNF-PitNETs according to sex and age.

METHODS

In this longitudinal study, we enrolled 431 consecutive patients with CNF-PitNETs who were treated at Seoul National University Hospital from 1997 to 2021. The patients underwent hormone function testing and visual field testing, and were subsequently followed up with imaging over a median duration of 66 months.

RESULTS

The median age of the patients was 53.0 years, and 37.1% (n = 160) were men. Men were older and harbored more macroadenomas than women. The annual tumor volume change was higher in men than in women (0.21 vs. 0.04 cm3/year, P < 0.001). The estimated cutoff value of age for significant tumor growth was 51 years. In men, the annual tumor volume change was similar across all age groups. In women, those aged ≤ 50 years showed significantly lower annual tumor volume change than those aged > 50 years (0.01, 0.11, and 0.17 cm3/year, P = 0.001). When comparing sexes within the same age group, the annual tumor volume changes was significantly lower for women than for men, only in patients aged ≤ 50 years (0.01 vs. 0.15 cm3/year, P < 0.001).

CONCLUSIONS

Among patients with CNF-PitNET, tumor growth was slower in women aged ≤ 50 years than in men and women aged > 50. These findings may guide the customization of surveillance strategies for CNF-PitNETs according to sex and age.

Secondary vs. primary pituitary xanthogranulomas: Which yellow is more mellow?

Pituitary xanthogranulomatomas (XG) are a rare pathological entity caused by accumulation of lipid laden macrophages and reactive granuloma formation usually triggered by cystic fluid leakage or hemorrhage. Our aim was to compare clinical characteristics and presenting features of patients with secondary etiology of XG and those with no identifiable founding lesion (primary -"pure" XG) in order to gain new insights into this rare pituitary pathology. In a retrospective review of 714 patients operated for sellar masses, at tertiary center, we identified 16 (2.24%) with histologically confirmed diagnosis of pituitary XG over the period of 7 years (2015-2021). Patients were further analyzed according to XG etiology: "pure"- XG (n = 8) with no identifiable founding lesion were compared to those with histological elements of pituitary tumor or cyst - secondary XG (n = 8). We identified 16 patients (11 male), mean age 44.8 ± 22.3 years, diagnosed with pituitary XG. Secondary forms were associated with Ratke's cleft cyst (RCC, n = 2) and pituitary adenoma (PA, n = 6). The most common presenting features in both groups were hypopituitarism (75%), headache (68.5%) and visual disturbances (37.5%). Predominance of male sex was noted (males 68.75%, females 31.25%), especially in patients with primary forms. Patients with primary pituitary XG were all males (p = 0.0256) and more frequently affected by panhypopituitarism (87.5% vs. 25%, p = 0.0406) compared to patients with secondary causes. Hyperprolactinemia was noted in pituitary tumor group with secondary etiology only (p = 0.0769). Majority of lesions were solid on magnetic resonance imaging - MRI (81.25%). Distinct clinical phenotype was observed dependent on the etiology of XG.

Single-cell transcriptomic analysis reveals tumor cell heterogeneity and immune microenvironment features of pituitary neuroendocrine tumors

BACKGROUND

Pituitary neuroendocrine tumors (PitNETs) are one of the most common types of intracranial tumors. Currently, the cellular characteristics of normal pituitary and various other types of PitNETs are still not completely understood.

METHODS

We performed single-cell RNA sequencing (scRNA-seq) on 4 normal samples and 24 PitNET samples for comprehensive bioinformatics analysis. Findings regarding the function of PBK in the aggressive tumor cells were validated by siRNA knockdown, overexpression, and transwell experiments.

RESULTS

We first constructed a reference cell atlas of the human pituitary. Subsequent scRNA-seq analysis of PitNET samples, representing major tumor subtypes, shed light on the intrinsic cellular heterogeneities of the tumor cells and tumor microenvironment (TME). We found that the expression of hormone-encoding genes defined the major variations of the PIT1-lineage tumor cell transcriptomic heterogeneities. A sub-population of TPIT-lineage tumor cells highly expressing GZMK suggested a novel subtype of corticotroph tumors. In immune cells, we found two clusters of tumor-associated macrophages, which were both highly enriched in PitNETs but with distinct functional characteristics. In PitNETs, the stress response pathway was significantly activated in T cells. While a majority of these tumors are benign, our study unveils a common existence of aggressive tumor cells in the studied samples, which highly express a set of malignant signature genes. The following functional experiments confirmed the oncogenic role of selected up-regulated genes. The over-expression of PBK could promote both tumor cell proliferation and migration, and it was also significantly associated with poor prognosis in PitNET patients.

CONCLUSIONS

Our data and analysis manifested the basic cell types in the normal pituitary and inherent heterogeneity of PitNETs, identified several features of the tumor immune microenvironments, and found a novel epithelial cell sub-population with aggressive signatures across all the studied cases.

Lung adenocarcinoma metastasis within a pituitary neuroendocrine tumor: a case report with review of literature

Collision tumors involving the metastasis of malignant neoplasms to pituitary neuroendocrine tumors (PitNETs) are extremely rare. We herein report a case involving a patient with lung adenocarcinoma metastasis within a PitNET who exhibited relatively rapid progression of neurological symptoms. A 75-year-old man who underwent tumor resection 36 and 18 years prior to presentation for bladder and colon cancer, respectively, without recurrence presented with bitemporal hemianopsia, ptosis, and diplopia of the right eye. Subsequent magnetic resonance imaging (MRI) revealed a tumor 3.2 cm in diameter that extended from the anterior pituitary gland to the suprasellar region. Gadolinium-enhanced MRI of the tumor showed heterogeneous contrast enhancement. Considering the relatively rapid progression of neurological symptoms, semi-emergency endoscopic endonasal transsphenoidal surgery was performed. Histopathological examination revealed a group of thyroid transcription factor-1- and napsin A-positive papillary proliferating cells intermingled with α-subunit- and steroidogenic factor-1-positive PitNET cells. Thus, the patient was diagnosed with lung adenocarcinoma metastasis within a gonadotroph PitNET. Genetic testing revealed the presence of an EGFR (Ex-19del) mutation, after which chemotherapy was initiated. Additional stereotactic radiotherapy was performed for the residual tumor in the sella turcica. With continued chemotherapy, good control of both the primary and metastatic tumors was noted after 24 months after surgery. Cases of malignant neoplasm metastasis within a PitNET are difficult to diagnose. In the case of a sella turcica tumor with relatively rapid progression of neurological symptoms, early surgical intervention is recommended given the possibility of a highly proliferative tumor and the need to obtain pathologic specimens.

Position statement on the diagnosis and management of acromegaly: The French National Diagnosis and Treatment Protocol (NDTP)

Acromegaly is a rare disease with prevalence of approximately 60 cases per million, slight female predominance and peak onset in adults in the fourth decade. Clinical diagnosis is often delayed by several years due to the slowly progressive onset of symptoms. There are multiple clinical criteria that define acromegaly: dysmorphic syndrome of insidious onset, symptoms related to the pituitary tumor (headaches, visual disorders), general signs (sweating, carpal tunnel syndrome, joint pain, etc.), complications of the disease (musculoskeletal, cardiovascular, pneumological, dental, metabolic comorbidities, thyroid nodules, colonic polyps, etc.) or sometimes clinical signs of associated prolactin hypersecretion (erectile dysfunction in men or cycle disorder in women) or concomitant mass-induced hypopituitarism (fatigue and other symptoms related to pituitary hormone deficiencies). Biological confirmation is based initially on elevated IGF-I and lack of GH suppression on oral glucose tolerance test or an elevated mean GH on repeated measurements. In confirmed cases, imaging by pituitary MRI identifies the causal tumor, to best determine management. In a minority of cases, acromegaly can be linked to a genetic predisposition, especially when it occurs at a young age or in a familial context. The first-line treatment is most often surgical removal of the somatotroph pituitary tumor, either immediately or after transient medical treatment. Medical treatments are most often proposed in patients not controlled by surgical removal. Conformal or stereotactic radiotherapy may be discussed on a case-by-case basis, especially in case of drug inefficacy or poor tolerance. Acromegaly should be managed by a multidisciplinary team, preferably within an expert center such as a reference or skill center for rare pituitary diseases.

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.

A case report of pituitary neuroendocrine tumor manifesting as severe conjunctival chemosis

BACKGROUND

Conjunctival chemosis (CC) is an extremely rare symptom of pituitary neuroendocrine tumor (PitNET). We report an extremely rare case of PitNET manifesting as severe CC.

CASE PRESENTATION

A 48-year-old male was admitted to our hospital with severe CC, proptosis, and ptosis of the right eye. Magnetic resonance imaging demonstrated the tumor mass invading the cavernous sinus (CS) with cystic lesion. The patient underwent emergent endoscopic transsphenoidal surgery, and the pathological diagnosis was PitNET. CC of the right eye remarkably improved after the surgery. Glucocorticoid therapy was performed for right oculomotor nerve palsy, which rapidly improved. The postoperative course was uneventful and the patient was discharged from our hospital without hormone replacement.

CONCLUSIONS

CC caused by CS invasion of PitNET can be cured by early surgical treatment. Therefore, PitNET is important to consider in the differential diagnosis of CC.

Endoscopic endonasal pituitary surgery: How we do it. Consensus statement on behalf of the EANS skull base section

Introduction and research question

The use of an endoscope in skull base surgery provides a panoramic close-up view over the intracranial structures from multiple angles with excellent illumination, thus permitting greater extent of resection of tumors arising at sellar area, mostly represented by PitNet - Pituitary neuroendocrine tumors, with higher likelihood of preserving vital/intact gland tissue. For this refined specialty of neurosurgery, unique skills need to be acquired along a steep learning curve.

Material and methods

EANS (European Association of Neurosurgical Societies) skull base section panelists were enrolled and 11 completed the survey: the goal was to provide a consensus statement of the endoscopic endonasal approach for pituitary adenoma surgery.

Results

The survey consisted of 44 questions covering demographics data (i.e., academic/non-academic center, case load, years of experience), surgical techniques (i.e., use of neuronavigation, preoperative imaging), and follow-up management.

Discussion and conclusions

In this paper we identified a series of tips and tricks at different phases of an endoscopic endonasal pituitary surgery procedure to underline the crucial steps to perform successful surgery and reduce complications: we took in consideration the principles of the surgical technique, the knowledge of the anatomy and its variations, and finally the importance of adjoining specialties experts.

Touch imprint cytology is useful for the intraoperative pathological diagnosis of PitNETs' surgical margins

Touch imprint cytology (TIC) and frozen section (FS) procedures are essential for intraoperative pathological diagnosis (IPD). They are invaluable tools for therapeutic decision-making, helping surgeons avoid under or overtreatment of patients. Pituitary neuroendocrine tumors (PitNETs) are generally small, slow-growing tumors with low-grade malignancy located at the base of the skull where it is impossible to maintain a wide tumor margin. Therefore, transsphenoidal surgery (TSS) should be performed with necessary caution, and with sufficient and minimal resection. Thus, this study aimed to evaluate the diagnostic accuracy of TIC for the diagnosis of PitNET and determine its ability to accurately evaluate the surgical margin compared to the FS procedure. A total of 104 fresh specimens from 28 patients who underwent TSS for PitNETs were examined using TIC and FS. TIC specimens were categorized according to the cell imprinting pattern. All specimens with a large number of neuroendocrine cells diffusely attached to the glass surfaces had PitNET components. Contrarily, no rich or diffuse cell attachments were observed in any non-tumoral endocrine cells. In conclusion, recognizing a pattern of endocrine cell adherence to glass is highly effective in IPD to certify the existence of a PitNET component.

Differentiation of silent corticotroph pituitary neuroendocrine tumors (PitNETs) from non-functioning PitNETs using kinetic analysis of dynamic MRI

PURPOSE

Silent corticotroph pituitary adenomas (SCAs)/pituitary neuroendocrine tumors (PitNETs) are common non-functioning pituitary adenomas (NFAs)/PitNETs with a clinically aggressive course. This study aimed to investigate the ability of time-intensity analysis of dynamic magnetic resonance imaging (MRI) for distinguishing adrenocorticotropic hormone (ACTH)-positive SCAs and ACTH-negative SCAs from other NFAs.

MATERIALS AND METHODS

We retrospectively evaluated the dynamic MRI findings of patients with NFAs. The initial slope of the kinetic curve (slopeini) obtained by dynamic MRI for each tumor was analyzed using a modified empirical mathematical model. The maximum slope of the kinetic curve (slopemax) was obtained by geometric calculation.

RESULTS

A total of 106 patients with NFAs (11 ACTH-positive SCAs, 5 ACTH-negative SCAs, and 90 other NFAs) were evaluated. The kinetic curves of ACTH-positive SCAs had significantly lesser slopeini and slopemax compared with ACTH-negative SCAs (P = 0.040 and P = 0.001, respectively) and other NFAs (P = 0.018 and P = 0.035, respectively). Conversely, the slopeini and slopemax were significantly greater in ACTH-negative SCAs than in NFAs other than ACTH-negative SCAs (P = 0.033 and P = 0.044, respectively). In receiver operating characteristic analysis of ACTH-positive SCAs and other NFAs, the area under the curve (AUC) values for slopeini and slopemax were 0.762 and 0748, respectively. In predicting ACTH-negative SCAs, the AUC values for slopeini and slopemax were 0.784 and 0.846, respectively.

CONCLUSIONS

Dynamic MRI can distinguish ACTH-positive SCAs and ACTH-negative SCAs from other NFAs.

Growth hormone proteoformics atlas created to promote predictive, preventive, and personalized approach in overall management of pituitary neuroendocrine tumors

Human growth hormone (GH) is the indispensable hormone for the maintenance of normal physiological functions of the human body, including the growth, development, metabolism, and even immunoregulation. The GH is synthesized, secreted, and stored by somatotroph cells in adenohypophysis. Abnormal GH is associated with various GH-related diseases, such as acromegaly, dwarfism, diabetes, and cancer. Currently, some studies found there are dozens or even hundreds of GH proteoforms in tissue and serum as well as a series of GH-binding protein (GHBP) proteoforms and GH receptor (GHR) proteoforms were also identified. The structure-function relationship of protein hormone proteoforms is significantly important to reveal their overall physiological and pathophysiological mechanisms. We propose the use of proteoformics to study the relationship between every GH proteoform and different physiological/pathophysiological states to clarify the pathogenic mechanism of GH-related disease such as pituitary neuroendocrine tumor and conduct precise molecular classification to promote predictive preventive personalized medicine (PPPM / 3P medicine). This article reviews GH proteoformics in GH-related disease such as pituitary neuroendocrine tumor, which has the potential role to provide novel insight into pathogenic mechanism, discover novel therapeutic targets, identify effective GH proteoform biomarker for patient stratification, predictive diagnosis, and prognostic assessment, improve therapy method, and further accelerate the development of 3P medicine.

Concurrent IgG4-related hypophysitis and clinically nonfunctioning gonadotroph pituitary neuroendocrine tumor

BACKGROUND

Some patients develop immunoglobulin G4 (IgG4)-related hypophysitis associated with systemic diseases. More than 30 cases of IgG4-related hypophysitis have been reported. However, biopsy has rarely been performed in these patients, and none have had an associated pituitary neuroendocrine tumor (PitNET). We present a case of concurrent IgG4-related hypophysitis and PitNET.

CASE PRESENTATION

A 56-year-old Japanese man arrived at the hospital with visual impairment, bitemporal hemianopia, and right abducens nerve palsy. Magnetic resonance imaging revealed pituitary body and stalk swelling as well as a small poorly enhanced right anterior lobe mass. Laboratory and loading test results suggested hypopituitarism. Because IgG4 level was elevated, a systemic examination was performed; multiple nodules were found in both lung fields. The diagnosis was based on an endoscopic transnasal biopsy of the pituitary gland. A histopathological examination revealed a marked infiltration of plasma cells into the pituitary gland, which was strongly positive for IgG4. The histological features of the resected tumor were consistent with those of gonadotroph PitNET, which was immunohistochemically positive for follicle-stimulating hormone-β and steroidogenic factor-1, and no plasma cell infiltration was observed. Based on the histopathological examination results, steroid therapy was initiated, which reduced pituitary gland size and serum IgG4 levels.

DISCUSSION AND CONCLUSIONS

This is the first reported case of IgG4-related hypophysitis with PitNET. Although no pathological findings indicating a relationship between the two conditions were found, we were able to preoperatively differentiate multiple lesions via detailed diagnostic imaging.

Aggressive pituitary tumors (PitNETs)

The majority of anterior pituitary tumors behave benignly, that is, they grow slowly and do not metastasize, and were therefore called adenomas. However, they would frequently invade adjacent structures, leading to recurrence. One of the misleading assumptions in their previous classification was the simplistic distinction made between adenoma and carcinoma. In the upcoming WHO 2022 classification, a new terminology will be introduced: pituitary neuroendocrine tumor (PitNET) which is consistent with that used for other neuroendocrine neoplasms. In general, aggressive PitNETs are invasive and proliferative tumors with frequent recurrences, resistant to conventional treatments, and yet virtually without metastases. At present, no single morphological or histological marker has been shown as yet to reliably predict their aggressive behavior. In terms of treatment, temozolomide (TMZ) had been considered promising and the sole therapeutic option for aggressive and malignant PitNETs following failure of standard therapies. However, recent reports have disclosed that TMZ does not provide long-term control of many aggressive PitNETs. A further multidisciplinary approach is necessary for both reliable prediction and successful management of aggressive PitNETs.

Usefulness of critical flicker fusion frequency measurement and its laterality for evaluating compressive optic neuropathy due to pituitary neuroendocrine tumors

Critical flicker fusion frequency (CFF) is a short but sensitive method for evaluating optic nerve function. We measured CFF in patients with pituitary neuroendocrine tumors (Pit-NETs) to assess its usefulness. Data from 184 patients with nonfunctioning Pit-NETs, who had been treated with transsphenoidal surgery and had no medical history of eye diseases, was used in this retrospective study. Visual acuity decline (VAD) was defined as > 0.10 reduction in logMAR visual acuity and CFF decline (CFD) was defined as CFF value < 35 Hz. Visual field defect (VFD) was evaluated by automated perimetry on a Humphrey visual field analyzer. Potential associations between abnormal test results and tumor height from the suprasellar were analyzed. Contact between the optic nerve or chiasma and the tumor was present and absent in 161 and 23 patients, respectively. In patients showing contact, the difference in CFF between the left and right eyes was larger (p = 0.0008), and the optimal cutoff value using the receiver operating characteristic curve was 3 Hz. Therefore, ≥ 3 Hz was considered positive for CFF laterality (CFL), the most prevalent condition. Tumor height was lower in patients with CFL positivity compared to those with VAD or VFD (p < 0.01). The prevalence of test abnormalities was the highest for small tumors compared to those of other tests. Changes in CFL permit early detection of Pit-NETs. Our results indicate that CFF laterality can be seen in the early stages of compressive optic neuropathy due to Pit-NET.

Update from the 5th Edition of the World Health Organization Classification of Head and Neck Tumors: Overview of the 2022 WHO Classification of Head and Neck Neuroendocrine Neoplasms

This review article provides a brief overview of the new WHO classification by adopting a question-answer model to highlight the spectrum of head and neck neuroendocrine neoplasms which includes epithelial neuroendocrine neoplasms (neuroendocrine tumors and neuroendocrine carcinomas) arising from upper aerodigestive tract and salivary glands, and special neuroendocrine neoplasms including middle ear neuroendocrine tumors (MeNET), ectopic or invasive pituitary neuroendocrine tumors (PitNET; formerly known as pituitary adenoma) and Merkel cell carcinoma as well as non-epithelial neuroendocrine neoplasms (paragangliomas). The new WHO classification follows the IARC/WHO nomenclature framework and restricts the diagnostic term of neuroendocrine carcinoma to poorly differentiated epithelial neuroendocrine neoplasms. In this classification, well-differentiated epithelial neuroendocrine neoplasms are termed as neuroendocrine tumors (NET), and are graded as G1 NET (no necrosis and < 2 mitoses per 2 mm²; Ki67 < 20%), G2 NET (necrosis or 2-10 mitoses per 2 mm², and Ki67 < 20%) and G3 NET (> 10 mitoses per 2 mm² or Ki67 > 20%, and absence of poorly differentiated cytomorphology). Neuroendocrine carcinomas (> 10 mitoses per 2 mm², Ki67 > 20%, and often associated with a Ki67 > 55%) are further subtyped based on cytomorphological characteristics as small cell and large cell neuroendocrine carcinomas. Unlike neuroendocrine carcinomas, head and neck NETs typically show no aberrant p53 expression or loss of RB reactivity. Ectopic or invasive PitNETs are subtyped using pituitary transcription factors (PIT1, TPIT, SF1, GATA3, ER-alpha), hormones and keratins (e.g., CAM5.2). The new classification emphasizes a strict correlation of morphology and immunohistochemical findings in the accurate diagnosis of neuroendocrine neoplasms. A particular emphasis on the role of biomarkers in the confirmation of the neuroendocrine nature of a neoplasm and in the distinction of various neuroendocrine neoplasms is provided by reviewing ancillary tools that are available to pathologists in the diagnostic workup of head and neck neuroendocrine neoplasms. Furthermore, the role of molecular immunohistochemistry in the diagnostic workup of head and neck paragangliomas is discussed. The unmet needs in the field of head and neck neuroendocrine neoplasms are also discussed in this article. The new WHO classification is an important step forward to ensure accurate diagnosis that will also form the basis of ongoing research in this field.

Overview of the 2022 WHO Classification of Neuroendocrine Neoplasms

In this review, we detail the changes and the relevant features that are applied to neuroendocrine neoplasms (NENs) in the 2022 WHO Classification of Endocrine and Neuroendocrine Tumors. Using a question-and-answer approach, we discuss the consolidation of the nomenclature that distinguishes neuronal paragangliomas from epithelial neoplasms, which are divided into well-differentiated neuroendocrine tumors (NETs) and poorly differentiated neuroendocrine carcinomas (NECs). The criteria for these distinctions based on differentiation are outlined. NETs are generally (but not always) graded as G1, G2, and G3 based on proliferation, whereas NECs are by definition high grade; the importance of Ki67 as a tool for classification and grading is emphasized. The clinical relevance of proper classification is explained, and the importance of hormonal function is examined, including eutopic and ectopic hormone production. The tools available to pathologists for accurate classification include the conventional biomarkers of neuroendocrine lineage and differentiation, INSM1, synaptophysin, chromogranins, and somatostatin receptors (SSTRs), but also include transcription factors that can identify the site of origin of a metastatic lesion of unknown primary site, as well as hormones, enzymes, and keratins that play a role in functional and structural correlation. The recognition of highly proliferative, well-differentiated NETs has resulted in the need for biomarkers that can distinguish these G3 NETs from NECs, including stains to determine expression of SSTRs and those that can indicate the unique molecular pathogenetic alterations that underlie the distinction, for example, global loss of RB and aberrant p53 in pancreatic NECs compared with loss of ATRX, DAXX, and menin in pancreatic NETs. Other differential diagnoses are discussed with recommendations for biomarkers that can assist in correct classification, including the distinctions between epithelial and non-epithelial NENs that have allowed reclassification of epithelial NETs in the spine, in the duodenum, and in the middle ear; the first two may be composite tumors with neuronal and glial elements, and as this feature is integral to the duodenal lesion, it is now classified as composite gangliocytoma/neuroma and neuroendocrine tumor (CoGNET). The many other aspects of differential diagnosis are detailed with recommendations for biomarkers that can distinguish NENs from non-neuroendocrine lesions that can mimic their morphology. The concepts of mixed neuroendocrine and non-neuroendocrine (MiNEN) and amphicrine tumors are clarified with information about how to approach such lesions in routine practice. Theranostic biomarkers that assist patient management are reviewed. Given the significant proportion of NENs that are associated with germline mutations that predispose to this disease, we explain the role of the pathologist in identifying precursor lesions and applying molecular immunohistochemistry to guide genetic testing.

Overview of the 2022 WHO Classification of Pituitary Tumors

This review summarizes the changes in the 5th Edition of the WHO Classification of Endocrine and Neuroendocrine Tumors that relate to the pituitary gland. The new classification clearly distinguishes anterior lobe (adenohypophyseal) from posterior lobe (neurohypophyseal) and hypothalamic tumors. Other tumors arising in the sellar region are also discussed. Anterior lobe tumors include (i) well-differentiated adenohypophyseal tumors that are now classified as pituitary neuroendocrine tumors (PitNETs; formerly known as pituitary adenomas), (ii) pituitary blastoma, and (iii) the two types of craniopharyngioma. The new WHO classification provides detailed histological subtyping of a PitNET based on the tumor cell lineage, cell type, and related characteristics. The routine use of immunohistochemistry for pituitary transcription factors (PIT1, TPIT, SF1, GATA3, and ERα) is endorsed in this classification. The major PIT1, TPIT, and SF1 lineage-defined PitNET types and subtypes feature distinct morphologic, molecular, and clinical differences. The "null cell" tumor, which is a diagnosis of exclusion, is reserved for PitNETs with no evidence of adenohypophyseal lineage differentiation. Unlike the 2017 WHO classification, mammosomatotroph and acidophil stem cell tumors represent distinct PIT1-lineage PitNETs. The diagnostic category of PIT1-positive plurihormonal tumor that was introduced in the 2017 WHO classification is replaced by two clinicopathologically distinct PitNETs: the immature PIT1-lineage tumor (formerly known as silent subtype 3 tumor) and the mature plurihormonal PIT1-lineage tumor. Rare unusual plurihormonal tumors feature multi-lineage differentiation. The importance of recognizing multiple synchronous PitNETs is emphasized to avoid misclassification. The term "metastatic PitNET" is advocated to replace the previous terminology "pituitary carcinoma" in order to avoid confusion with neuroendocrine carcinoma (a poorly differentiated epithelial neuroendocrine neoplasm). Subtypes of PitNETs that are associated with a high risk of adverse biology are emphasized within their cell lineage and cell type as well as based on clinical variables. Posterior lobe tumors, the family of pituicyte tumors, include the traditional pituicytoma, the oncocytic form (spindle cell oncocytoma), the granular cell form (granular cell tumor), and the ependymal type (sellar ependymoma). Although these historical terms are entrenched in the literature, they are nonspecific and confusing, such that oncocytic pituicytoma, granular cell pituicytoma, and ependymal pituicytoma are now proposed as more accurate. Tumors with hypothalamic neuronal differentiation are classified as gangliocytomas or neurocytomas based on large and small cell size, respectively. This classification sets the standard for a high degree of sophistication to allow individualized patient management approaches.

Challenges in the Diagnosis of Pituitary Neuroendocrine Tumors

Detailed analysis of cytodifferentiation and hormone production has classified pituitary neuroendocrine tumors (PitNETs) in a formal system that reflects the lineage differentiation of nontumorous adenohypophysial cells as well as subtypes of tumors that have predictive value. In addition, tumors composed of cells that lack terminal differentiation are well characterized. To comply with the proposal to create an overarching classification of neuroendocrine neoplasia, these tumors are now called PitNETs rather than adenomas. The next important step will be to relinquish the term "pituitary carcinoma" for metastatic PitNETs that remain well differentiated, and to alter the terminology used for tumors that are not terminally differentiated to reflect only their immature lineage. The existence of mixed neuroendocrine and non-neuroendocrine neoplasms (MiNENs) similar to those at other body sites is proven by mixed craniopharyngiomas with PitNETs. As with other NETs, these neoplasms should be reported with synoptic data that guide completeness of reporting. A formal system of grading should be created, but not only based on proliferation, as these tumors have shown the prognostic value of cytodifferentiation. A formal system of staging should also be devised to complement grade in the thorough and accurate diagnosis of tumors that arise from adenohypophysial cells.

Genomics and Epigenomics of Pituitary Tumors: What Do Pathologists Need to Know?

Molecular pathology has advanced our understanding of many tumors and offers opportunities to identify novel therapies. In the pituitary, the field has uncovered several genetic mutations that predispose to pituitary neuroendocrine tumor (PitNET) development, including MEN1, CDKN1B, PRKRIα, AIP, GPR101, and other more rare events; however, these genes are only rarely mutated in sporadic PitNETs. Recurrent genetic events in sporadic PitNETs include GNAS mutations in a subset of somatotroph tumors and ubiquitin-specific peptidase mutations (e.g., USP8, USP48) in some corticotroph tumors; to date, neither of these has resulted in altered management, and instead, the prognosis and management of PitNETs still rely more on cell type and subtype as well as local growth that determines surgical resectability. In contrast, craniopharyngiomas have either CTNNB1 or BRAF^V600E mutations that correlate with adamantinomatous or papillary morphology, respectively; the latter offers the opportunity for targeted therapy. DICER1 mutations are found in patients with pituitary blastoma. Epigenetic changes are implicated in the pathogenesis of the more common sporadic pituitary neoplasms including the majority of PitNETs and tumors of pituicytes.

Structure, Function, and Morphology in the Classification of Pituitary Neuroendocrine Tumors: the Importance of Routine Analysis of Pituitary Transcription Factors

The traditional approach to the diagnosis of primary adenohypophyseal cell proliferations uses hormone immunohistochemistry to classify pituitary neuroendocrine tumors (PitNETs). The routine application of immunolocalization of pituitary transcription factors (SF1, PIT1, TPIT, ERα, and recently GATA3) along with adenohypophyseal hormones has taught us critical lessons that are discussed in this communication. We point out that appropriate patient care requires accurate diagnosis and is critical in the era of precision medicine. A misdiagnosis can result in far greater health care costs than the cost of accurate tumor classification and may have other unintended consequences. We provide additional insights about confusing findings in genomic studies, emphasizing that high-quality pathology is essential for strong science and translational research.

World Health Ozganization 2017 Classification of Pituitary Tumors

The 2017 (fourth edition) World Health Organization Classification of Endocrine Tumors has recommended major changes in classification of tumors of the pituitary gland and region. In addition to the accurate tumor subtyping, assessment of the tumor proliferative potential (mitotic and/or Ki-67 index) and other clinical parameters such as tumor invasion is strongly recommended in individual cases for consideration of clinically aggressive adenomas. It is expected that this new WHO classification will establish more uniform biologically and clinically groups of pituitary tumors and contribute to understanding of clinical outcomes for patients harboring pituitary tumors.

Frequency and Role of CDKN2A Deletion in High-Risk Pituitary Neuroendocrine Tumors

The underlying mechanisms of aggressive pituitary neuroendocrine tumors (pitNETs) are still unclear. The p16 protein, encoded by the CDKN2A tumor suppressor gene on chromosome 9p21, is commonly reported to be lost in numerous types of cancer. For this reason, this study examined to examine the status of homozygous deletion of CDKN2A in high-risk pitNETs. Thirty-eight high-risk pitNETs (30 male, 8 female) were analyzed for CDKN2A deletion by fluorescent in situ hybridization (FISH). Demographic characteristics such as sex, patient age at operation, and sellar magnetic resonance imaging findings including tumor size and invasion status were recorded. The frequency of CDKN2A homozygous deletion by FISH was 3/38 (7.89%) in the high-risk pitNET group. All of these three cases with CDKN2A homozygous deletion were invasive densely granulated lactotroph tumors (p = 0.000). CDKN2A deletion was not correlated with patient age, sex, cavernous sinus invasion (CSI), and tumor size (p > 0.05). The Ki-67 proliferation index was significantly correlated with CDKN2A homozygous deletion (p = 0.003). The mean Ki-67 proliferation index was 10.7% in pitNETs with CDKN2A homozygous deletion and the Ki-67 proliferation index in the whole study group was 4.1%. CSI was significantly correlated with the morphofunctional tumor types including lactotroph tumor, invasive null cell tumor, and invasive gonadotroph tumor (p = 0.021). These findings suggest a close correlation between inactivation of p16 gene and invasive lactotroph tumors. Further investigations are needed to expand on the mechanism of p16 (CDKN2A) gene deletion in high-risk pitNETs.

Expression of programmed death-ligand 1 (PD-L1) in human pituitary neuroendocrine tumor

OBJECTIVE

To explore the programmed death-ligand 1 (PD-L1) expression in varied subtypes of pituitary neuroendocrine tumors with assessment of their clinical behavior at diagnosis and follow-up.

METHODS

We conducted a retrospective monocentric study, including all patients operated in the Academic Hospital of Angers (France) for a pituitary neuroendocrine tumor between 2012 and 2018. PDL-1 immunostaining was performed using a European Conformity-In Vitro Diagnostic-labeled anti-PDL1 antibody (clone 22C3). PD-L1 immunostaining was evaluated as the percentage of tumor cells showing positive membrane staining, into four grades: grade 0 = < 1%, grade 1 = 1 to 5%, grade 2 = 6 to 49% and grade 3 = ≥ 50%. PD-L1 expression was compared with tumor features (secretion, proliferation, invasion) and outcome.

RESULTS

The study included 139 pituitary neuroendocrine tumors, including 84 (60%) nonfunctioning adenomas. Twenty-five pituitary neuroendocrine tumors were PD-L1 positive (18%), including 3 grade 3, 8 grade 2 and 14 grade 1. PD-L1 expression was not different between functioning and nonfunctioning adenomas (p = 0.26). Among 16 tumors with proliferative markers (Ki-67 ≥ 3% and p53 positive), only one was PD-L1 positive.

CONCLUSION

In our series, PD-L1 was expressed in a rather small proportion of PitNET (18%), and this immune marker was not associated with any biological characteristic or behavior of the pituitary tumors. Thus, PD-L1 staining may be necessary before considering PD-L1 blockage in pituitary neuroendocrine tumors, in case of therapeutic impasse.

An Institutional Experience of Tumor Progression to Pituitary Carcinoma in a 15-Year Cohort of 1055 Consecutive Pituitary Neuroendocrine Tumors

Pituitary carcinoma is a rare disease, defined by the presence of cerebrospinal or distant metastasis of a pituitary neuroendocrine tumor (PitNET). To review our institutional experience of pituitary carcinoma, we searched the database of the UHN Endocrine Oncology Site group and the University Health Network pathology laboratory information system from 2001 to 2016. Among 1055 PitNETs from 1169 transsphenoidal resections, we identified 4 cases of pituitary carcinoma, indicating that pituitary carcinoma represents around 0.4% of PitNETs. All four patients were women. The age at initial presentation ranged from 23 to 54 years. Two patients had Cushing disease with corticotroph tumors; one was initially a densely granulated corticotroph tumor that evolved to become sparsely granulated, while the other was a Crooke cell tumor. One patient had a functioning sparsely granulated lactotroph tumor and one had a clinically silent poorly differentiated PIT1 lineage tumor. Apart from a relatively high Ki67 labeling index (≥ 10%) in three tumors, there were no cytomorphologic features at the time of initial presentation that could predict subsequent metastatic behavior. The time from diagnosis of the pituitary neuroendocrine tumor to the diagnosis of malignancy was 3 to 14 years. Therapies included somatostatin analogs, external beam radiotherapy, chemotherapies including capecitabine/temozolomide, everolimus, sunitinib, bevacizumab, and peptide receptor radionuclide therapy (PRRT). One patient died of disease 18 years after initial diagnosis, underscoring the protracted course of this ultimately fatal neuroendocrine malignancy.

The 2017 World Health Organization classification of tumors of the pituitary gland: a summary

The 4th edition of the World Health Organization (WHO) classification of endocrine tumors has been recently released. In this new edition, major changes are recommended in several areas of the classification of tumors of the anterior pituitary gland (adenophypophysis). The scope of the present manuscript is to summarize these recommended changes, emphasizing a few significant topics. These changes include the following: (1) a novel approach for classifying pituitary neuroendocrine tumors according to pituitary adenohypophyseal cell lineages; (2) changes to the histological grading of pituitary neuroendocrine tumors with the elimination of the term "atypical adenoma;" and (3) introduction of new entities like the pituitary blastoma and re-definition of old entities like the null-cell adenoma. This new classification is very practical and mostly based on immunohistochemistry for pituitary hormones, pituitary-specific transcription factors, and other immunohistochemical markers commonly used in pathology practice, not requiring routine ultrastructural analysis of the tumors. Evaluation of tumor proliferation potential, by mitotic count and Ki-67 labeling index, and tumor invasion is strongly recommended on individual case basis to identify clinically aggressive adenomas. In addition, the classification offers the treating clinical team information on tumor prognosis by identifying specific variants of adenomas associated with an elevated risk for recurrence. Changes in the classification of non-neuroendocrine tumors are also proposed, in particular those tumors arising in the posterior pituitary including pituicytoma, granular cell tumor of the posterior pituitary, and spindle cell oncocytoma. These changes endorse those previously published in the 2016 WHO classification of CNS tumors. Other tumors arising in the sellar region are also reviewed in detail including craniopharyngiomas, mesenchymal and stromal tumors, germ cell tumors, and hematopoietic tumors. It is hoped that the 2017 WHO classification of pituitary tumors will establish more biologically and clinically uniform groups of tumors, make it possible for practicing pathologists to better diagnose these tumors, and contribute to our understanding of clinical outcomes for patients harboring pituitary tumors.

Overview of the 2017 WHO Classification of Pituitary Tumors

This review focuses on discussing the main changes on the upcoming fourth edition of the WHO Classification of Tumors of the Pituitary Gland emphasizing histopathological and molecular genetics aspects of pituitary neuroendocrine (i.e., pituitary adenomas) and some of the non-neuroendocrine tumors involving the pituitary gland. Instead of a formal review, we introduced the highlights of the new WHO classification by answering select questions relevant to practising pathologists. The revised classification of pituitary adenomas, in addition to hormone immunohistochemistry, recognizes the role of other immunohistochemical markers including but not limited to pituitary transcription factors. Recognizing this novel approach, the fourth edition of the WHO classification has abandoned the concept of "a hormone-producing pituitary adenoma" and adopted a pituitary adenohypophyseal cell lineage designation of the adenomas with subsequent categorization of histological variants according to hormone content and specific histological and immunohistochemical features. This new classification does not require a routine ultrastructural examination of these tumors. The new definition of the Null cell adenoma requires the demonstration of immunonegativity for pituitary transcription factors and adenohypophyseal hormones Moreover, the term of atypical pituitary adenoma is no longer recommended. In addition to the accurate tumor subtyping, assessment of the tumor proliferative potential by mitotic count and Ki-67 index, and other clinical parameters such as tumor invasion, is strongly recommended in individual cases for consideration of clinically aggressive adenomas. This classification also recognizes some subtypes of pituitary neuroendocrine tumors as "high-risk pituitary adenomas" due to the clinical aggressive behavior; these include the sparsely granulated somatotroph adenoma, the lactotroph adenoma in men, the Crooke's cell adenoma, the silent corticotroph adenoma, and the newly introduced plurihormonal Pit-1-positive adenoma (previously known as silent subtype III pituitary adenoma). An additional novel aspect of the new WHO classification was also the definition of the spectrum of thyroid transcription factor-1 expressing pituitary tumors of the posterior lobe as representing a morphological spectrum of a single nosological entity. These tumors include the pituicytoma, the spindle cell oncocytoma, the granular cell tumor of the neurohypophysis, and the sellar ependymoma.