| Abstract|| |
Pituicytoma is a distinct sellar or supracellar tumor which originates from specialized glial cells of neurohypophyses and infundibulum known as pituicytes. Because of its sellar location patients present with headache, visual disturbance, and endocrine abnormalities. Pituicytoma is difficult to diagnose on neuroimaging as radiological features overlap with other more common tumors of this region. Thus, diagnosis is established by histopathology and immunohistochemistry of resected tumor only. Pituicytomas are composed of bipolar spindle cells arranged as fascicles and are immunoreactive for TTF-1, S100p, and vimentin. These tumors are extremely rare and only around 70 published cases are known in literature. We report a case of suprasellar SOL in a 58-year-old male who presented with headache and gradual visual deterioration in both eyes. He was diagnosed as a case of pituicytoma based on light microscopy findings and immunohistochemical expression of TTF-1, vimentin, S100p, and bcl-2.
Keywords: Headache, pituicytoma, suprasellar, TTF-1, vision
|How to cite this article:|
Mishra S, Guleria P. Pituicytoma: Case report of a rare suprasellar tumor. Indian J Pathol Microbiol 2021;64:145-8
| Introduction|| |
Pituicytomas were first described by Brat et al. in 2000 as low grade glial tumors of neurohypophyses or infundibulum which are composed of plump spindle cells having fibrillary cytoplasm arranged as sheets and short fascicles. Since then, around 70 cases of pituicytomas have been described in literature. The largest case series published in 2019 by Viaene et al. describes clinical, histopathological, immunohistochemical, and molecular characteristics of pituicytomas. This neoplasm occurs in adults (mean age; 50 years) as a slowly growing non-hormonally active sellar/suprasellar mass. Patients present with complaints of headache, visual disturbance, and features of hypopituitarism such as amenorrhea, decreased libido and fatigue due to compression of optic chiasma and pituitary. Pituicytoma is difficult to diagnose on neuroimaging and is often reported as a pituitary adenoma. MRI shows a well-circumscribed suprasellar or purely intrasellar mass which is iso-intense on T1WI with homogenous contrast enhancement. Diagnosis is made on histopathology of resected tumor and confirmed by immunohistochemical expression of TTF-1, S100 protein, and vimentin. We describe a case of suprasellar space occupying lesion in a 58-year-old male who was diagnosed as a case of pituicytoma on histopathology and IHC.
| Case History|| |
A 58-year-old male presented with complaints of bilateral diminution of vision and headache for a duration of three years. MRI brain showed a well-marginated suprasellar mass lesion with altered signal intensity measuring 39 × 35 × 37 mm with good post-contrast enhancement. The tumor was surgically resected through trans-sphenoidal approach and was noted to be extremely vascular on intra-operative examination.
Histopathology showed a tumor composed of elongated to plump spindle cells having abundant eosinophilic fibrillary cytoplasm. Tumor cells were arranged as fascicles and in storiform pattern with prominent vascularity [Figure 1]. There was no evidence of oncocytic change or cytoplasmic granularity. Mitotic activity was low and significant nuclear pleomorphism or atypia was not seen. Immunohistochemistry showed nuclear expression of TTF-1 and diffuse positivity for vimentin and bcl-2 [Figure 2]. S100 protein was focally positive. Tumor cells were immuno-negative for neuroendocrine markers and GFAP. Thus, based on light microscopy features, expression of pituicyte maker (TTF-1) and absence of neuroendocrine marker expression a diagnosis of pituicytoma was established.
|Figure 1: Histopathologic features of pituicytoma (H&E) showed tumor cells arranged as fascicles and in storiform pattern (a) with prominent vascularity (b and c). Tumor cells have moderate amount of eosinophilic cytoplasm, elongated to spindled nuclei with indistinct nucleoli (d). There was no evidence of oncocytic change or cytoplasmic granularity. Mitotic activity was low and significant nuclear pleomorphism or atypia was not seen|
Click here to view
|Figure 2: Immunohistochemistry showed diffuse cytoplasmic expression of vimentin (a), nuclear expression of TTF-1 (b) and bcl-2 in tumour cells (c). GFAP expression was seen in adjacent glial tissue but not in tumor cells (d). Neuroendocrine markers like synaptophysin and chromagranin were not expressed|
Click here to view
| Discussion|| |
Pituicytoma is described in WHO Classification of Tumors of Central Nervous System as a circumscribed and low grade (WHO Grade I) glial tumor of neurohypophyses and infundibulum. The cell of origin is believed to be pituicytes, which are specialized glial cells in the neurohypophysis. This view is supported by nuclear expression of TTF-1 in pituicytomas and normal pituicytes of neurohypophyses. Spindle Cell Oncocytoma and Granular Cell Tumor of the sellar region are two other tumors which are believed to originate from pituicytes and have similar immunohistochemical expression profile. These three tumors are thus believed to constitute a spectrum of neoplasms which have a common origin from pituicytes but varied morphology.
Pituicytomas are tumors of adults with a mean age of 53 years (age range of 30–77 years) and a Male:Female ratio of 1.2:1. Symptoms occur because of mass effect and compression of adjacent structures like optic chiasma, pituitary, and infundibulum. Presenting complaints are headache, visual disturbances, and pituitary hormone abnormalities such as amenorrhea, hyperprolactinaemia, and decreased libido. Presenting complaints in our case were headache and gradual bilateral loss of vision. There were no signs of hormonal imbalance and serum prolactin level was normal.
On neuroimaging, pituicytomas appear as well-circumscribed suprasellar or combined sellar and suprasellar masses. Few purely intrasellar cases are also reported. Tumor size ranges between 1 and 3.5 cm with an average size of 2 cm. They are iso-intense with uniform contrast enhancement on MRI. Common differentials include other sellar/suprasellar tumors such as pituitary adenoma, meningioma, craniopharyngioma, and glioma., Our patient also had a well-defined suprasellar mass measuring 35 × 39 mm on MRI with good post contrast enhancement. [Table 1] compares the clinical, radiological and immunohistochemical features of pituicytomas with case series published by Bret et al. in 2010 and Viaene et al. in 2019.
|Table 1: Table comparing clinical, radiological and immunohistochemical features of pituicytoma noted in our study with two case series published by Bret et al. in 2010 and Viaene et al. in 2019.|
Click here to view
On light microscopy, pituicytomas are tumors of elongated to plump spindle cells which are arranged as intersecting fascicles, sheets, and storiform pattern. Cytoplasm is moderate, eosinophilic, and without cytoplasmic granularity or vacuolation. Nuclei are moderate in size, round to elongated with indistinct nucleoli. Significant nuclear pleomorphism is not seen and mitotic activity is low. The tumor is richly vascular and numerous blood vessels of variable diameter are seen.
Closely related tumors of sellar and suprasellar region are Spindle Cell Oncocytoma and Granular Cell tumor of sellar region which have similar clinical and radiological features. However, they can be differentiated from pituicytoma on histopathology. Spindle cell Oncocytoma have spindled to epithelioid cells with mild to moderate nuclear atypia and oncocytic to clear cytoplasm. Granular cell tumor of sellar region has polygonal cells with abundant granular cytoplasm which gives positive staining on PAS stain. These cells have a sheet-like or nodular arrangement and perivascular lymphocytic infiltrates., Pituicytomas show strong and diffuse vimentin and S100 protein expression on immunohistochemistry. Nuclear staining for TTF-1 establishes its origin from pituicytes of normal pituitary gland which also express this marker. bcl-2 and GFAP expression are variable and patchy. Absence of expression of neuroendocrine markers like synaptophysin and chromogranin helps to differentiate it from pituitary adenoma, which form an important differential of sellar and suprasellar tumors. Our case too showed diffuse expression of TTF-1 (nuclear) and vimentin. S100 protein expression was patchy. GFAP and neuroendocrine markers were negative with a low ki-67 index of <2% [Figure 2].
Few studies conducted to assess molecular alterations in these rare tumors have reported alterations in MAP kinase pathway involving mutations of HRAS and KDR genes. Reports on BRAFV600E mutation are conflicting; one study has identified presence of this mutation while others have conflicting results. IDH1R132H mutation has not been reported in any study.
Treatment and prognosis
Pituicytomas are low grade, slow growing tumors which are managed by surgical resection alone. They do not recur if gross total surgical resection has been done. Tumor recurrence has been seen in cases that underwent sub-total resection. Distant metastasis and malignant transformation has not been reported till date. We have reported this case so that our clinical, radiological, and histopathological findings can add to the available knowledge and help clinicians and pathologists diagnose this extremely rare but treatable neoplasm.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms. In the form the patient(s) has/have given his/her/their consent for his/her/their images and other clinical information to be reported in the journal. The patients understand that their names and initials will not be published and due efforts will be made to conceal their identity, but anonymity cannot be guaranteed.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
| References|| |
Brat DJ, Scheithauer BW, Staugaitis SM, Holtzman RN, Morgello S, Burger PC. Pituicytoma: A distinctive low-grade glioma of the neurohypophysis. Am J Surg Pathol 2000;24:362-8.
Viaene AN, Lee EB, Rosenbaum JN, Nasrallah IM, Nasrallah MP. Histologic, immunohistochemical, and molecular features of pituicytomas and atypical pituicytomas. Acta Neuropathol Commun 2019;7:69.
Covington MF, Chin SS, Osborn AG. Pituicytoma, spindle cell oncocytoma, and granular cell tumor: Clarification and meta-analysis of the World Literature since 1893. Am J Neuroradiol 2011;32:2067-72.
Brat DJ, Wesseling P, Fuller GN, Roncaroli F. Pituicytoma. In: Louis DN, Ohgaki H, Wiestler OD, Cavenee WK, Ellison DW, et al. editors. WHO Classification of Tumours of the Central Nervous System, Revised. 4th
ed.. Lyon: IARC; 2016. p. 332-3.
Lee EB, Tihan T, Scheithauer BW, Zhang PJ, Gonatas NK. Thyroid transcription factor 1 expression in sellar tumors: A histogenetic marker? J Neuropathol Exp Neurol 2009;68:482-8.
Zygourakis CC, Rolston JD, Lee HS, Partow C, Kunwar S, Aghi MK. Pituicytomas and spindle cell oncocytomas: Modern case series from the University of California, San Francisco. Pituitary 2015;18:150-8.
Romero-Rojas AE, Melo-Uribe MA, Barajas-Solano PA, Chinchilla-Olaya SI, Escobar LIR, Hernandez-Walteros DM. Spindle cell oncocytoma of the adenohypophysis. Brain Tumor Pathol 2011;28:359-64.
Park SJ, Chang YH, Yang N-R, Seo EK. Granular cell tumor in the pituitary stalk: A case report. Brain Tumor Res Treat 2015;3:60-3.
Mete O, Lopes MB, Asa SL. Spindle cell oncocytomas and granular cell tumors of the pituitary are variants of pituicytoma. Am J Surg Pathol 2013;37:1694-9.
Chandler J, Ogiwara H, Shafizadeh S, Dubner S, Raizer J. Spindle cell oncocytoma of the pituitary and pituicytoma: Two tumors mimicking pituitary adenoma. Surg Neurol Int 2011;2:116.
] [Full text]
Department of Pathology and Molecular Medicine, Army Hospital (Research and Referral), Delhi Cantt, New Delhi - 110 010
Source of Support: None, Conflict of Interest: None
[Figure 1], [Figure 2]