[Combined neuronal and endocrine tumors of the sellar region]

[The 2017 WHO classification of pituitary tumors]

The 2017 WHO classification of pituitary tumors is still based on structural analyses and expression of various pituitary hormones. Three innovations have to be considered: (1) The expression of pituitary transcription factors Pit‑1, T‑Pit and SF‑1. (2) The term "atypical adenoma" was replaced by "aggressive adenoma". (3) The three tumor types of the neurohypophysis (pituicytoma, spindle cell oncocytoma, granular cell tumor) are defined by their common expression of TTF‑1. Craniophyryngiomas are identified as adamantinomatous type by focal nuclear expression of β‑catenin or as papillary type by demonstration of BRAF V600E mutation. Further primary tumors of the pituitary are extremely rare. These and also the other tumors of the sellar region can be structurally very similar to pituitary adenomas but can be-nearly without exception-differentiated by immunocytochemistry.

Pituitary Gangliocytoma Producing TSH and TRH: A Review of "Gangliocytomas of the Sellar Region"

PURPOSE

Pituitary gangliocytomas (GCs) are rare neuronal tumors that present with endocrinological disorders, such as acromegaly, amenorrhea-galactorrhea syndrome, and Cushing's disease. Most pituitary GCs coexist with pituitary adenomas pathologically and are diagnosed as mixed gangliocytoma-adenomas. Herein, we report a case of 45-year-old man who presented with the syndrome of inappropriate secretion of thyroid-stimulating hormone (SITSH) and discuss the pathogenesis of pituitary GCs.

METHODS

Pituitary magnetic resonance imaging showed an 8-mm homogeneous and poorly enhanced mass inside the pituitary gland. Endoscopic transsphenoidal surgery was performed under a preoperative diagnosis of thyrotroph adenoma. However, the tumor was finally diagnosed as gangliocytoma without an adenomatous component. The tumor was further analyzed via immunohistochemistry and electron microscopy. Additionally, we searched MEDLINE and PubMed for previously published cases of isolated pituitary GCs and analyzed the reported clinicopathological findings.

RESULTS

The patient showed complete clinical and endocrinological recovery after an operation. The tumor was positive for thyrotropin (TSH), TSH-releasing hormone (TRH), Pit-1, GATA-2, and most neuronal markers. Electron microscopy demonstrated the presence of intracytoplasmic secretory granules and neuronal processes. Co-secreting hypothalamic and pituitary hormone inside the tumor indicated autocrine/paracrine endocrinological stimulation.

CONCLUSION

Herein, we report a case of SITSH caused by an isolated pituitary gangliocytoma, expressing both TSH and TRH, which, to our best knowledge, is the first reported case of such a condition. The multidirectional differentiation and multihormonal endocrine characteristics of these tumors indicate that they are a member of neuroendocrine neoplasms, further supporting that they are derived from neural crest cells.

Mixed gangliocytoma-pituitary adenoma containing GH and GHRH co-secreting adenoma cells

SUMMARY

A 67-year-old woman with a past history of type 2 diabetes mellitus presented with worsening glycemic control. She had some acromegaly symptoms and magnetic resonance imaging demonstrated a pituitary tumor. Endocrinological examination found the resting growth hormone (GH) level within the normal range, but elevated insulin-like growth factor 1 level. A 75 g oral glucose tolerance test showed inadequate suppression of nadir GH levels. Acromegaly due to GH-secreting pituitary tumor was diagnosed. The patient underwent endoscopic transsphenoidal surgery resulting in gross total removal of the tumor and recovered well postoperatively. Histological examination of the tumor showed coexistence of relatively large gangliocytoma cells and pituitary adenoma cells, suggesting mixed gangliocytoma-pituitary adenoma. In addition, colocalization of GH and GH-releasing hormone (GHRH) in pituitary adenoma cells was revealed, so the adenomatous components were more likely to produce GHRH in our mixed gangliocytoma-pituitary adenoma case. Mixed gangliocytoma-pituitary adenoma is very rare, and the present unique case demonstrated only the adenomatous components associated with GHRH production.

LEARNING POINTS

Sellar gangliocytoma coexisting with pituitary adenoma is recognized as a mixed gangliocytoma-pituitary adenoma and is very rare. A proposed developmental mechanism of growth hormone (GH)-secreting mixed gangliocytoma-pituitary adenoma involves GH-releasing hormone (GHRH) produced by the gangliocytic components promoting the growth of tumor including GH-secreting adenomatous components. Since our present case indicated that the adenomatous components of mixed gangliocytoma-pituitary adenoma could secrete both GH and GHRH simultaneously, progression of GH-secreting mixed gangliocytoma and pituitary adenoma may involve exposure to spontaneously produced GHRH due to the adenomatous components.

Ganglioglioma of the adenohypophysis mimicking pituitary adenoma: A case report and review of the literature

INTRODUCTION

Ganglioglioma is a generally benign tumor, mostly occurring in patients <30 years old. Temporal lobe is most frequently involved. Up to now, only 3 cases were reported of ganglioglioma in the pituitary gland, all being confined to the neurohypophysis. Here, we are the first to report an adenohypophysis ganglioglioma.

CASE PRESENTATION

A 43-year-old woman presented with chronic headache was referred to our hospital. Magnetic resonance imaging (MRI) indicated pituitary adenoma. Endoscopic transnasal transsphenoidal surgery was performed. The tumor was rich in blood supply, with tough texture, therefore only subtotal resection was conducted. Pathology analysis revealed an adenohypophysial tumor composed of dysplastic ganglion cells and neoplastic glial cells collided with nonspecific hyperplasia of pituitary cells. Immunohistochemistry revealed positive staining of synaptophysin, glial-fibrillary acidic protein, and CD34. The results were consistent with the diagnosis of ganglioglioma. After the surgery the patient recovered well except developing cerebrospinal fluid rhinorrhea, which was controlled by lumbar drainage. MRI 6 months later did not show any sign of progression.

CONCLUSION

According to the findings of our case, concerns should be raised considering ganglioglioma as a differential diagnosis of mass located in the sellar region. Furthermore, an ideal management strategy for pituitary ganglioglioma is not known; therefore, more cases and long-term follow-up are needed to enrich our knowledge of the diagnosis, treatment, and prognosis of this rare intracranial lesion.

Anterior Gray Matter Pituicytic Heterotopia with Monomorphic Anterior Pituitary Cells: A Variant of Nonsecretory Pituitary Adenoma Neuronal Choristoma? Report of a Rare Case and Review of the Literature

BACKGROUND

Mixed tumors of adenomatous and neuronal cells in the sellar region are an uncommon finding. The origins of these heterogeneous tumors are unknown, and management remains unsettled. We report a very rare case of anterior gray matter pituicytic heterotopia with monomorphic anterior pituitary cells that likely represents a variant of nonsecreting pituitary adenoma neuronal choristoma (PANCH) with no ganglion cells. We also review the current literature for the various clinical presentations of PANCH.

CASE DESCRIPTION

A 49-year-old female complaining of headache, blurred vision, and hair loss was found to have a nonsecretory sellar mass with compression of the optic chiasm on magnetic resonance imaging (MRI). The mass was excised via a transsphenoidal procedure. Histological analysis of tissue sections revealed heterotopic gray matter with reactive gliosis without ganglion cells or Herring bodies. Only 1 smear exhibited characteristics of a pituitary adenoma.

CONCLUSIONS

The overall findings were most consistent with a variant of PANCH. At a postoperative follow-up of 4.5 years, there was resolution of visual symptoms, and the residual sellar mass was stable on MRI. Neuronal choristoma is hypothesized to originate from embryonal pituitary or hypothalamus, or by differentiation from pituitary adenoma cells. Surgery is the cornerstone of management, and the clinical course appears to be similar to that of nonfunctioning pituitary adenoma in reported cases.

[New aspects of tumor pathology of the pituitary]

Pituitary adenomas have to be studied in detail for structural characteristics, especially regarding the degree of granulation and immunohistochemical hormone expression, such as growth hormone (GH), prolactin, adrenocorticotropic hormone (ACTH), thyroid stimulating hormone (TSH), follicle stimulating hormone (FSH), luteinizing hormone (LH) and proliferation markers (e.g. Ki-67 and p53) for correlation to clinical data and assessment of the prognosis. If histological and immunostaining data do not correlate to the patient data, explanations for the discrepancies must be found. All active adenoma types can also be present as inactive, so-called silent adenomas showing the same features. An increased Ki-67 index (> 3%), significant nuclear expression of protein p53 and mitoses are characteristic of atypical adenomas. Up to now the biological relevance of these atypical adenomas, especially their role as preneoplasms for pituitary carcinomas has not been fully elucidated. The only proof of a pituitary carcinoma is the existence of metastases. Extensive local invasion and a greatly increased Ki-67 index are not sufficient for this diagnosis. Craniopharyngiomas have to be classified into adamantinomatous types (intrasellar and suprasellar) and papillary types (only suprasellar). Regressive changes are found in adamantinomatous types only. Strong regression may lead to difficulties in the differential diagnosis of Rathke's cleft cysts with squamous metaplasia. Demonstration of nuclear expression of beta-catenin in these cases enables the diagnosis of craniopharyngioma. Papillary craniopharyngiomas are characterized by BRAF mutations that may be helpful in the differential diagnosis. All pituicytomas of the neurohypophysis, all spindle cell oncocytomas of the anterior pituitary and all granular cell tumors of the posterior pituitary express thyroid transcription factor 1 (TTF-1) and are thought to be variants of a common uniform spindle cell tumor of the pituitary.

Pituitary adenoma-neuronal choristoma is a pituitary adenoma with ganglionic differentiation

The presence of ganglion cells within an endocrine pituitary tumor has been named hamartoma, choristoma, gangliocytoma, or most recently pituitary adenoma-neuronal choristoma (PANCH). The presence of neuronal differentiation in regular pituitary adenomas has been previously suggested, however, its origin, the extent of its presence, and the relationship between the neuronal elements and the pituitary adenoma remain uncertain. Thus, to further explore the neuronal potential of pituitary tumors, we used immunohistochemistry on pituitary tumors of different grades, with a neuronal antigen protein (NeuN) antibody as a specific marker for mature neuronal differentiation. We found NeuN expression in 26.47% (9/34) cases of pituitary tumors without ganglionic differentiation (7 adenomas, 1 atypical adenoma and 1 pituitary carcinoma), in addition to NeuN expression in pituitary adenomas with ganglionic cells (2/2). Thus, neuronal expression is an innate property of pituitary adenomas. We propose that the rare presence of ganglionic cells in pituitary adenomas is not the result of a separate lesion or "collision sellar tumors", as previously suggested, but a ganglionic neuronal differentiation in an endocrine neoplasm. The ganglionic cells may be arising from uncommitted stem/progenitor cells that contain both neuronal and endocrine properties. A label of "pituitary adenoma with ganglionic differentiation" would better reflect the dual differentiation in a neuroendocrine tumor than the current label "PANCH".

[Pituitary gland tumors]

Pituitary adenomas must be clearly differentiated from other tumors of the sellar region (especially meningiomas, granular cell tumors, chordomas and germinomas), which may look very similar. The sub-classification of adenomas depends on the methods used, in particular the immunostaining for pituitary hormones. This sub-classification is not necessary in every case, but must be performed if unusual findings are observed during surgery or if surgery is unsuccessful and radiation or drug-therapy is planned. Special structures and non-immunohistochemical stainings are very helpful for typing adenomas. We differentiated monohormonal densely or sparsely granulated GH-cell adenomas, monohormonal sparsely or very rarely densely granulated prolactin cell adenomas, monohormonal densely or sparsely ACTH-cell adenomas, monohormonal TSH-cell adenomas and FSH/LH cell adenomas from bihormonal adenomas of mammosomatotroph or GH/prolactin cell type or of the acidophil stem cell adenoma type. The number of plurihormonal adenomas decreased with the use of improved monoclonal antibodies. Clinically inactive adenomas are classified as null cell adenomas, oncocytic adenomas or FSH/LH-cell adenomas. These appear as subtypes of one entity deriving from the gonadotroph cell type. Craniopharyngiomas are classified into adamantinous and papillary types, which are not only structurally but also clinically different. If adamantinous craniopharyngiomas show very strongly regressive changes, immunostaining for keratin may be necessary to identify the squamous epithelia for the demonstration of craniopharyngioma.

Intrasellar gangliocytomas associated with acromegaly

The present study was designed to investigate the immunohistochemical characteristics of gangliocytomas associated with growth hormone (GH)-secreting pituitary adenomas. In our surgical collection of 476 GH-secreting adenoma cases, we examined tumor tissue from 6 patients (1.3%). All 6 patients were women, ranging from 29 to 52 years (mean, 40.3 +/- 9.5 SD) of age. Among 470 patients with GH-secreting adenomas without gangliocytoma, there were 255 female and 215 male patients. The preponderance of female patients with gangliocytomas was striking. Histological examination of the resected specimens showed areas of ganglion cells and adenomatous cells. Ganglion cell lesions were stained positively for synaptophysin (4 of 4; 100%) and neurofilament (4 of 4; 100%) as well as GH-releasing hormone (5 of 6; 83.3%). Subtypes of GH cell adenomas included 4 cases of sparsely granulated type and 2 cases of mixed GH and prolactin (PRL) cell adenomas. Based on these findings, we hypothesized that the intrasellar gangliocytoma promoted the growth of the pituitary adenoma by chronic overstimulation from excess GH-releasing hormone.

Cushing's disease: a surgical view

The management of adrenocorticotropic hormone (ACTH)-dependent Cushing's disease implies difficulties in the differential diagnosis, in the detection of minute pituitary adenomas, as well as in the radical removal of invasive adenomas. Magnetic resonance imaging (MRI) is unspecific and often negative in minute adenomas of three or less millimeters diameter. The trias of detectable ACTH, suppression of cortisol in the high-dose dexamethasone test, and stimulation in the corticotropin-releasing-hormone (CRH)-test has a high accuracy to prove pituitary dependency. In unclear cases, the use of inferior petrosal sinus sampling (IPSS) or cavernous sinus sampling (CSS) for the exclusion of ectopic ACTH-syndrome is currently advised especially in cases where cranial MRI is negative. The reliability of these methods to localize the mostly lateralized microadenomas is still discussed. Transsphenoidal microsurgical adenomectomy, the accepted primary therapy of Cushing's disease, has been published from experienced pituitary centers with remission rates ranging from 70% to 98% in the last decade. False diagnosis (pseudo-Cushing, ectopic ACTH-syndrome), incorrect adenoma localization by IPSS or CSS, and the rate of minute or non-resectable invasive tumors influence the results. The handling of minute specimen implies problems for surgeon and pathologist. Intraoperative tumor localization was improved by ACTH measurement from the cavernous sinus and the adenoma itself, by cytology, and frozen sections. The histology of the anterior lobe (rate of Crooke's cells) bears information of clinical relevance. Invasive macroadenomas may deserve repeat microsurgery, medical treatment, and radiosurgery.

'Gangliocytomas' of the pituitary: a heterogeneous group of lesions with differing histogenesis

Hamartomatous or neoplastic ganglion cells in the sella turcica are an unusual cause of symptoms. They have been reported in association with a functioning or nonfunctioning pituitary adenoma, with pituitary cell hyperplasia, and occasionally as masses unassociated with an adenoma, again with variable endocrinologic findings. Fewer than 50 cases of intrasellar ganglion cell lesions have been reported in the literature, only six of them associated with Cushing's syndrome. We describe the clinicopathologic features of another eight patients, three of whom presented with acromegaly, four with apparently nonfunctioning adenohypophyseal masses, and one with Cushing's syndrome. On histology, six of them were found to have sparsely granulated growth hormone (GH)-producing adenomas with ganglion cell areas, one appeared to have a gangliocytoma not associated with an adenoma, whereas the eighth had a ganglion cell lesion in the posterior pituitary. The morphologic and immunohistochemical findings suggest that the ganglion cell component of seven of these tumors has resulted from neuronal differentiation in a GH-producing adenoma, despite the lack of demonstrable adenoma in one case. A true sellar "gangliocytoma" or hamartoma of ectopic hypothalamic-type neurons appears to be a rarer explanation for the presence of ganglion cells in a pituitary biopsy.