WHO 2016 classification: changes and advancements in the diagnosis of miscellaneous primary CNS tumours

This short review highlights significant changes and recent findings incorporated to varying extent in the WHO 2016 definition of a variety of tumours, including peripheral nerve sheath tumours, meningiomas, mesenchymal nonmeningothelial tumours, melanocytic tumours, lymphomas and histiocytic tumours, germ cell tumours and non‐neuroendocrine pituitary tumours. Most notable classification changes include: adding ‘hybrid nerve sheath tumours’ to the spectrum of benign nerve sheath tumours; an updated definition of atypical meningioma (WHO grade II), including cases with brain invasion; recognizing dural solitary fibrous tumour (SFT) and haemangiopericytoma (HPC) as a single tumour entity characterized by NAB2 and STAT6 gene fusions for which the term SFT/HPC was chosen; recognizing that pituitary granular cell tumour, spindle cell oncocytoma, and pituicytoma all share nuclear expression of TTF‐1, possibly representing a spectrum of a single nosological entity derived from posterior pituitary glial cells. The most significant diagnostic markers which have emerged include: inactivation of NF1, CDKN2A, and PRC2 components, SUZ12 and EED in MPNST, leading to neurofibromin and H3K27me3 expression loss; GNAQ and GNA11 mutations in CNS primary melanocytic tumours; BRAFV600E mutation in histiocytic tumours (Langerhans cell histiocytosis and Erdheim‐Chester disease) and papillary craniopharyngioma, which provides both a diagnostic marker in the appropriate pathological setting and a therapeutic target. The WHO 2016 Classification has balanced cutting‐edge knowledge on the molecular characteristics of the miscellaneous CNS tumours reviewed here with a practical approach for their daily diagnostic work‐up. Much more progress can be expected in the classification of these neoplasms in the near future.     

A new prognostic clinicopathological classification of pituitary adenomas: a multicentric case–control study of 410 patients with 8 years post-operative follow-up

Pituitary adenomas are currently classified by histological, immunocytochemical and numerous ultrastructural characteristics lacking unequivocal prognostic correlations. We investigated the prognostic value of a new clinicopathological classification with grades based on invasion and proliferation. This retrospective multicentric case–control study comprised 410 patients who had surgery for a pituitary tumour with long-term follow-up. Using pituitary magnetic resonance imaging for diagnosis of cavernous or sphenoid sinus invasion, immunocytochemistry, markers of the cell cycle (Ki-67, mitoses) and p53, tumours were classified according to size (micro, macro and giant), type (PRL, GH, FSH/LH, ACTH and TSH) and grade (grade 1a: non-invasive, 1b: non-invasive and proliferative, 2a: invasive, 2b: invasive and proliferative, and 3: metastatic). The association between patient status at 8-year follow-up and age, sex, and classification was evaluated by two multivariate analyses assessing disease- or recurrence/progression-free status. At 8 years after surgery, 195 patients were disease-free (controls) and 215 patients were not (cases). In 125 of the cases the tumours had recurred or progressed. Analyses of disease-free and recurrence/progression-free status revealed the significant prognostic value (p < 0.001; p < 0.05) of age, tumour type, and grade across all tumour types and for each tumour type. Invasive and proliferative tumours (grade 2b) had a poor prognosis with an increased probability of tumour persistence or progression of 25- or 12-fold, respectively, as compared to non-invasive tumours (grade 1a). This new, easy to use clinicopathological classification of pituitary endocrine tumours has demonstrated its prognostic worth by strongly predicting the probability of post-operative complete remission or tumour progression and so could help clinicians choose the best post-operative therapy.     

The relationship between neuropeptide Y expression and headache in pituitary tumours

Patients with pituitary tumours often present with disabling headache but there is no clear relationship between tumour size and headache. Neuropeptide Y (NPY) has been identified in pituitary tumours and may serve as a biochemical marker of the propensity for headache. Using immunohistochemical techniques we examined 27 consecutive pituitary adenoma specimens for NPY (including one normal postmortem control anterior pituitary specimen). A separate observer divided the patients into two groups: headache and non-headache. The association between the presence of NPY and headache was tested. NPY positive immunoreactivity was seen in 13 tumour specimens (50%, 13 of 26 pituitary tumour specimens), characterized by cytoplasmic and nuclear staining patterns. There was no significant association between the presence of NPY and headache (chi(2) = 0.9, P = 0.34). We did not observe NPY in the normal anterior pituitary control specimen. NPY was present in four of five (80%) growth hormone-secreting tumours and two of two (100%) prolactinomas, compared with four of 11 (36%) non-functioning adenomas. The mechanism of many pituitary tumour-associated headaches remains undetermined. The significance of NPY positivity in pituitary tumours is unknown, although the results of this study may implicate this peptide in the control of somatotroph and lactotroph activity. Our data do not support a clear role for NPY pituitary tumour-associated headache.     

Spindle cell oncocytoma of the adenohypophysis - a clinicopathological and ultrastructural study of two cases

Spindle cell oncocytoma (SCO) of the pituitary gland is a relatively recently established, very rare subtype of adenohypophysis tumours that was introduced as a distinct clinicopathological entity in the fourth edition of WHO classification of the central nervous system tumours (2007). It is non-endocrine neoplasm of the anterior pituitary that occurs in adults and usually follows a benign clinical course, corresponding to WHO grade I. Up to now, pituitary SCO have been reported occasionally and only 14 cases of SCO have been documented in the literature. Because of their rarity, the pathogenesis and natural history of these tumours have not been fully characterized. We report two additional cases of SCO occurring in females aged 63 years (Case 1) and 65 years (Case 2), who presented with pan-hypopituitarism, headache and visual field defect. In both cases, the magnetic resonance imaging showed solid sellar mass of moderate size with suprasellar extension. The clinical and radiological features suggested non-functioning pituitary macroadenomas without evidence of invasive growth. One patient presented with tumour recurrence 3 years after undergoing the previous surgical removal of tumour, which was initially misdiagnosed as schwannoma. The first tumour was removed by transsphenoidal surgery and the second one by frontal craniotomy. Histologically and immunohistochemically, both tumours displayed the features typical for SCO of the pituitary. They were composed of interwoven fascicles of spindle cells exhibiting abundant eosinophilic cytoplasm of oncocytic or granular appearance. Mitoses were rarely observed and necrosis was absent. In one case, the advanced lymphocytic infliltration was observed within neoplastic tissue. The tumour cells exhibited immunoreactivity for S-100 protein, galectin-3, vimentin and epithelial membrane antigen but they were negative for GFAP, anterior pituitary neuroendocrine markers (prolactin, growth hormone, TSH, ACTH, FSH, LH), chromogranin, synaptophysin, cytokeratin CK (AE1/AE3), smooth muscle actin, desmin, CD34 and CD68. MIB1 labeling index did not exceed 10%. Ultrastructurally, the tumour cells were rich in mitochondria with lamellar cristae. Moreover, in Case 2 some tumour cells showed a number of giant mitochondria with severely destructed internal matrix. Spindle cell oncocytoma of the anterior pituitary is often misdiagnosed entity of uncertain histogenesis. It should be considered in the differential diagnosis of various sellar-region lesions of oncocytic morphology.     

Prolactinomas, dopamine agonists and headache: two case reports.

Headache is a common problem in patients with pituitary tumours. Small pituitary lesions can cause debilitating headache, suggesting that the size of the pituitary tumour may not be the only causal factor in pituitary-related headache. We present two cases of prolactinoma-associated headache. The first case has a clinical diagnosis of short-lasting unilateral headache attacks with conjunctival injection and tearing (SUNCT). The second case has a clinical diagnosis of hemicrania continua and idiopathic stabbing headache. In each case, the administration of dopamine agonists has led to an exacerbation of symptoms. We review the relevant literature to understand the pathophysiological implications of these cases.     

The tumour microenvironment of pituitary neuroendocrine tumours

The tumour microenvironment (TME) includes a variety of non-neoplastic cells and non-cellular elements such as cytokines, growth factors and enzymes surrounding tumour cells. The TME emerged as a key modulator of tumour initiation, progression and invasion, with extensive data available in many cancers, but little is known in pituitary tumours. However, the understanding of the TME of pituitary tumours has advanced thanks to active research in this field over the last decade. Different immune and stromal cell subpopulations, and several cytokines, growth factors and matrix remodelling enzymes, have been characterised in pituitary tumours. Studying the TME in pituitary tumours may lead to a better understanding of tumourigenic mechanisms, identification of biomarkers useful to predict aggressive disease, and development of novel therapies. This review summarises the current knowledge on the different TME cellular/non-cellular elements in pituitary tumours and provides an overview of their role in tumourigenesis, biological behaviour and clinical outcomes.     

No relationship between vasoactive intestinal polypeptide expression and headache in pituitary tumours

BACKGROUND: Clinical studies have noted the common presentation of pituitary tumours with significant headache. This has been considered to be one, or a combination of, increased cranial pressure, tumour size with dural stretch, or cavernous sinus invasion. Newer hypotheses suggest an association between the presence of pituitary tumour-associated headaches and the expression and release of nociceptive substances. Vasoactive intestinal polypeptide (VIP), a marker of the cranial parasympathetic system, is increased during acute attacks of some primary headaches, and with its expression in the pituitary may link some pituitary tumours to their headache presentations. METHODS: Using immunohistochemical techniques, VIP expression in pituitary tumour specimens was examined to determine if there was a relationship between the presence or absence of pituitary-associated headache and the expression of VIP immunoreactivity (VIP-IR). A qualitative analysis of the VIP-IR in pituitary cells was performed by observers blinded to the headache status of each patient. The presence of VIP-IR and headache were treated as binary variables and associations tested with chi-square tests. RESULTS: Forty-five per cent of specimens positive for VIP were from patients presenting with headache. There was no statistically significant association between the presence of VIP-IR and headache (chi(2) = 0.077, P = 0.781). CONCLUSION: Although the significance of VIP positivity in pituitary tumour-associated headache is unknown it seems unrelated to headache. It remains possible that the mechanism of these headaches relates to the production of either an as yet unidentified peptide, or a combination of nociceptive peptides.     

Pituitary tumours in adolescence: clinical behaviour and neuroimaging features of seven cases.

The clinicopathologic features of seven paediatric patients with pituitary adenomas (2 male, 5 female; mean age 14.3 years) were reviewed. There were three non-functioning adenomas, three prolactinomas, and one growth hormone producing adenoma. Five patients presented with visual field deficits, and six patients had endocrine symptoms, which included menstrual irregularities in all female patients, pubertal delay in two females, and growth delay and gigantism in one case each. On neuroimaging studies, five adenomas showed parasellar extension, while the remaining two prolactinomas were intrasellar microadenomas. While two patients with prolactinomas received good results with bromocriptine treatment alone, the remaining five patients underwent either craniotomy or transsphenoidal surgery. Postoperatively, visual disturbances improved markedly in all patients. Two patients also received replacement hormonal therapy. While six patients have been stable for 3.6 years on average, one non-functioning tumour recurred 2 years after the initial transcranial subtotal resection of the tumour. Although there are still many unknowns concerning the biology and optimal treatments for paediatric pituitary adenomas, many of them are assumed to be relatively rapidly growing tumours, while others merely have an earlier tumour genesis than in adults.     

Tumour vascularity is of prognostic significance in adult, but not paediatric astrocytomas

Astrocytomas are the commonest type of brain tumours in adults and children. Although the most reliable prognostic indicators have been shown consistently to be patient age and tumour histological grade, biological progression in these tumours is inevitable and the overall prognosis has remained poor. Due to the evidence that vascular changes are important histological features of astrocytomas, the aim of this study was to investigate prognostic significance of tumour vascularity in paediatric and adult astrocytomas. Study population consisted of 70 patients (45 adult and 25 children) with histologically proven diagnosis of astrocytoma with no history of previous therapy. Histological quantification of tumour vascularity was performed using three different methods: microvessel density, vascular grading and Chalkley counting. Histological classification and grading were also assessed using the World Health Organization system. In contrast to the results in paediatric astrocytomas, tumour vascularity in adult tumours correlated significantly with postoperative survival by univariate analysis (P < 0.05). Microvessel density appeared to be an independent indicator of prognosis by multivariate analysis (P = 0.001). Likewise, patients with microvessel density of 70 or greater had significantly shorter survival than the remaining group (P < 0.001). Patient age and tumour histological grade were also correlated with survival. We conclude that histological quantification of tumour vascularity is a significant prognosticator in adult astrocytomas, but not in children. Our data do not support the validity of applications of antiangiogenic agents in paediatric astrocytic tumours, particularly pilocytic astrocytomas.     

Ghrelin stimulates adrenocorticotrophic hormone (ACTH) secretion by human ACTH-secreting pituitary adenomas in vitro

Ghrelin is a brain-gut peptide with wide-ranging endocrine, metabolic, cardiovascular and neural effects. Ghrelin, like its synthetic counterparts, the growth hormone (GH) secretagogues, has been shown to markedly stimulate adrenocorticotrophic hormone (ACTH) and cortisol secretion in humans and the ACTH-releasing effect of GH secretagogues is even greater in patients with pituitary ACTH-secreting tumours. Furthermore, these tumours synthesize ghrelin itself, suggesting an intrapituitary ghrelin circuit. The aim of the present study was to evaluate the effect of ghrelin on ACTH secretion by human pituitary corticotroph tumours in vitro to test the functionality of this circuit. Nine ACTH-secreting pituitary tumours (four microadenomas, five macroadenomas) were collected during surgery and incubated with 10-100 nM human ghrelin or with 10 nM human corticotrophin-releasing hormone (CRH). Control experiments were performed in rat anterior pituitary primary cultures. ACTH secretion was assessed after 4 h and 24 h incubation by immunometric assay. After 4 h of incubation with ghrelin, medium ACTH concentrations were two- to ten-fold higher compared to ACTH concentrations in unstimulated wells. The ACTH-releasing effect of ghrelin was significantly less than the response elicited by 10 nM CRH (up to 40-fold) Similar results were obtained after 24 h of incubation and a superimposable response pattern was observed in rat anterior pituitary primary cultures. The present study demonstrates that the endogenous GH secretagogue, ghrelin, stimulates ACTH secretion directly from human tumoural corticotrophs, as well as from normal rat pituitary, and indicates that the marked ACTH release elicited by ghrelin in patients with Cushing's disease in vivo is due, at least in part, to its action on the pituitary tumour. However, the reversal of the response pattern reported in vivo, with ghrelin proving a lesser stimulant than CRH in vitro, suggests that additional, suprapituitary mechanisms are involved in the in vivo response. Moreover, these data uphold the concept of a functional intratumoural ghrelin paracrine circuit in human corticotroph adenomas.     

Combining Cadherin Expression with Molecular Markers Discriminates Invasiveness in Growth Hormone and Prolactin Pituitary Adenomas

Although growth hormone (GH)‐ and prolactin (PRL)‐secreting pituitary adenomas are considered benign, in many patients, tumour growth and/or invasion constitute a particular challenge. In other tumours, progression relies in part on dysfunction of intercellular adhesion mediated by the large family of cadherins. In the present study, we have explored the contribution of cadherins in GH and PRL adenoma pathogenesis, and evaluated whether this class of adherence molecules was related to tumour invasiveness. We have first established, by quantitative polymerase chain reaction and immunohistochemistry, the expression profile of classical cadherins in the normal human pituitary gland. We show that the cadherin repertoire is restricted and cell‐type specific. Somatotrophs and lactotrophs express mainly E‐cadherin and cadherin 18, whereas N‐cadherin is present in the other endocrine cell types. This repertoire undergoes major differential modification in GH and PRL tumours: E‐cadherin is significantly reduced in invasive GH adenomas, and this loss is associated with a cytoplasmic relocalisation of cadherin 18 and catenins. In invasive prolactinomas, E‐cadherin distribution is altered and is accompanied by a mislocalisation of cadherin 18, β‐catenin and p120 catenin. Strikingly, de novo expression of N‐cadherin is present in a subset of adenomas and cells exhibit a mesenchymal phenotype exclusively in invasive tumours. Binary tree analysis, performed by combining the cadherin repertoire with the expression of a subset of known molecular markers, shows that cadherin/catenin complexes play a significant role in discrimination of tumour invasion.     

Review: personalized mice: modelling the molecular heterogeneity of medulloblastoma

Medulloblastoma, the most common malignant paediatric brain tumour, is thought to arise from mutations in progenitors or stem cells in the cerebellum. Recent molecular analyses have highlighted the heterogeneity of these tumours, and demonstrated that they can be classified into at least four major subtypes that differ in terms of gene expression, genomic gains and losses, epidemiology and patient outcome. Along with analysis of human tumours, a variety of animal models of medulloblastoma have been developed using transgenic and knockout technology as well as somatic gene delivery. These models have provided valuable insight into the origins of the disease and the signalling pathways that control tumour growth. But the degree to which current models recapitulate the heterogeneity of the human disease remains unclear. Here we review the recent literature on the genomics of medulloblastoma and discuss the relationship of mouse models to the subtypes of the disease. Judicious use of existing models, and generation of additional models for poorly studied subtypes of medulloblastoma, will increase our understanding of tumour biology and allow evaluation of novel approaches to treatment of the disease.     

Growth hormone secreting pituitary adenoma with admixed gangliocytoma and ganglioglioma

Pituitary adenomas are the most common tumours found in the sellar region and, when both functioning and non-functioning adenomas are combined, account for 7–15% of primary brain tumours in adults. Rarely, admixed or discrete groups of cells comprising two or more tumour subtypes are seen; the so-called ‘collision tumour’. We present a case of a 54-year-old-woman with a growth hormone-secreting pituitary adenoma admixed with both ganglioglioma and gangliocytoma. The possible mechanisms by which this may occur include a pre-existing gangliocytoma promoting the development of pituitary adenoma by hypersecretion of releasing hormones or aberrant migration of hypothalamic neurons in early embryogenesis.     

CNS embryonal tumours: WHO 2016 and beyond

Embryonal tumours of the central nervous system (CNS) present a significant clinical challenge. Many of these neoplasms affect young children, have a very high mortality and therapeutic strategies are often aggressive with poor long‐term outcomes. There is a great need to accurately diagnose embryonal tumours, predict their outcome and adapt therapy to the individual patient's risk. For the first time in 2016, the WHO classification took into account molecular characteristics for the diagnosis of CNS tumours. This integration of histological features with genetic information has significantly changed the diagnostic work‐up and reporting of tumours of the CNS. However, this remains challenging in embryonal tumours due to their previously unaccounted tumour heterogeneity. We describe the recent revisions made to the 4th edition of the WHO classification of CNS tumours and review the main changes, while highlighting some of the more common diagnostic testing strategies.     

Plasminogen activator inhibitor-I and tumour growth, invasion, and metastasis

In recent decades, evidence has been accumulating showing the important role of urokinase-type plasminogen activator (uPA) in growth, invasion, and metastasis of malignant tumours. The evidence comes from results with animal tumour models and from the observation that a high level of uPA in human tumours is associated with a poor patient prognosis. It therefore initially came as a surprise that a high tumour level of the uPA inhibitor plasminogen activator inhibitor-I (PAI-I) is also associated with a poor prognosis, the PAI-I level in fact being one of the most informative biochemical prognostic markers. We review here recent investigations into the possible tumour biological role of PAI-I, performed by animal tumour models, histological examination of human tumours, and new knowledge about the molecular interactions of PAI-I possibly underlying its tumour biological functions. The exact tumour biological functions of PAI-I remain uncertain but PAI-I seems to be multifunctional as PAI-I is expressed by multiple cell types and has multiple molecular interactions. The potential utilisation of PAI-I as a target for anti-cancer therapy depends on further mapping of these functions.     

Neuropathological diagnosis of brain tumours

With recent progress in radiological, pathological, immunohistochemical, molecular and genetic diagnoses, the characterisation of brain tumours has improved. The last World Health Organization (WHO) Classification of Tumours of the Central Nervous System was done in 2007, based on morphological features, growth pattern and molecular profile of neoplastic cells, defined malignancy grade. The neuropathological diagnosis and the grading of each histotype are based on identification of histopathological criteria and immunohistochemical data. Molecular and genetic profiles may identify different tumour subtypes varying in biological and clinical behaviour, indicating prognostic and predictive factors. In order to investigate new therapeutic approaches, it is important to study the molecular pathways responsible for proliferation, invasion, angiogenesis, and anaplastic transformation. Different prognostic and predictive factors for glioma patients were identified by genetic studies, such as the loss of heterozygosis on chromosome 1p and 19q for oligodendrogliomas, proangiogenic factors such as Vascular Endothelial Growth Factor for glioblastomas and the methylation status of gene promoter of MethylGuanine-MethylTransferase. In conclusion, the prognostic evaluation and the therapeutic strategies for patients depend on the synthesis of histological diagnosis, malignancy grade, gene-molecular profile, radiological images, surgical resection and clinical findings (age, tumour location, and "performance status").