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Neuroimaging characteristics and growth pattern on magnetic resonance imaging in a 52-year-old man presenting with pituicytoma: a case report
© Kosuge et al.; licensee BioMed Central Ltd. 2012
Received: 12 May 2012
Accepted: 11 August 2012
Published: 18 September 2012
Pituicytoma is a rare neoplasm of the neurohypophysis. To the best of our knowledge there have been no reports of pituicytoma in which long-term magnetic resonance imaging observation was performed. We calculated the doubling time of the tumor volume and described the growth pattern of a pituicytoma.
A 52-year-old Japanese man with a history of decreased libido was found to have a sellar and suprasellar mass. He underwent transsphenoidal surgery, but only a small specimen was obtained because of intraoperative bleeding. The tentative histological diagnosis was schwannoma. He noticed bitemporal hemianopsia 7 years later. A follow-up magnetic resonance imaging disclosed a tumor volume doubling time of 3830 days. Transcranial gross-total tumor resection was performed. The lesion consisted of elongated and plump tumor cells that were arranged in a fascicular or storiform pattern and were positive for S-100 protein and focally positive for glial fibrillary acidic protein. The final histological diagnosis was pituicytoma.
Pituicytoma is a slow-growing tumor, but the growth rate may change during follow-up.
Pituicytoma is a rare neoplasm in adults. It corresponds to a low-grade astrocytoma of the neurohypophysis that presumably arises from pituicytes of the stalk and posterior lobe of the pituitary gland[1, 2]. This tumor is included in the 2007 World Health Organization (WHO) classification of tumors of the central nervous system as a WHO grade 1 tumor. We report a case of pituicytoma and discuss the neuroimaging characteristics and surgical findings.
Pituicytoma is a very rare tumor of the adult neurohypophysis with only about 50 reported cases. Several authors have also used the term ‘pituicytoma’ to refer to other tumors in the neurohypophysis, especially pilocytic astrocytoma and granular cell tumor. The 2007 WHO classification of tumors of the central nervous system defines pituicytoma as a low-grade glial neoplasm of the neurohypophysis or infundibulum that originates from pituicytes.
The neuroimaging characteristics of pituicytomas are nonspecific. Pituicytomas have been described to be located within the sellar, the suprasellar region or both. Although there were not many reports on the CT findings of pituicytomas, in the case reported by Wolfe et al., the tumor showed sellar enlargement and bony remodeling on CT scan. MRI shows an isointense mass on T1-weighted images, hyperintensity on T2-weighted images, and homogeneous enhancement with gadolinium. Therefore, the radiological differential diagnosis should include other sellar or suprasellar tumors including meningioma, craniopharyngioma, hemangiopericytoma, granular cell tumor, and pilocytic astrocytoma. It is often difficult to identify these tumors in preoperative neuroradiological findings, especially for nonfunctioning pituitary adenoma in our case. However, the histologic appearance and immunohistochemical findings are distinctive[2, 3]. Pituicytomas contain elongated spindle cells that are arranged in a bundle or storiform pattern with no granular component. Staining is positive for S-100, focally positive for GFAP and EMA, and negative for PAS. In the current case, we believe that the resected specimen in the first surgery stained negatively for GFAP because of the minimal resection that was possible in this surgery.
In previous reports, the most common symptoms at presentation of pituicytoma have been headache (38.9%) followed by visual field defect (31.5%). Only one patient presented with diabetes insipidus, despite pituicytomas arising from the posterior pituitary gland or infundibulum. Nakasu et al. suggested that pituicytomas start to grow in the posterior lobe or lower portion of the stalk, so the upper neurohypophysis might have to compensate for the loss of function.
Surgery is the main treatment for pituicytoma. Tumor recurrence has occurred in some patients after subtotal resection, but there have been no reports of recurrence or enlargement in patients who underwent total or gross total resection[1, 5]. Thus, the best chance for cure appears to be gross total resection because partial resection carries a significant possibility of recurrence. In our first surgery, we were able to achieve only a biopsy because of significant bleeding. Several other reports have also described considerable bleeding during surgery[1–3, 5–14], whereas others have indicated that bleeding was easily controlled[4, 5]. We compared the tumor size for these two types, based on definition of the sagittal diameter of the pons as 26.6mm and estimation of the tumor size from sagittal MRI. The mean diameter did not differ significantly between hemorrhagic tumors (22.9mm) and non-hemorrhagic tumors (21.4mm). Therefore, the risk of intraoperative bleeding does not seem to depend on the tumor size. Some patients who underwent subtotal resection were also treated with postoperative radiotherapy[1, 7, 8]. However, the value of adjuvant therapy for pituicytomas is anecdotal and unclear in the absence of evidence from a large series[2, 6].
Pituicytoma is an extremely rare tumor of the neurohypophysis. To the best of our knowledge this is the first report of the TVDT of pituicytoma. Pituicytoma is a slow-growing tumor, but may enlarge rapidly without malignant change. The relatively slow growth of pituicytoma and the possible change in growth rate during follow up should be recognized in determining the most appropriate treatment approach.
Written informed consent was obtained from the patient for publication of this case report and any accompanying images. A copy of the written consent is available for review by the Editor-in-Chief of this journal.
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