Journal of Postgraduate Medicine Medknow Publications and Staff Society of Seth GS Medical College and KEM Hospital, Mumbai, India ISSN: 0022-3859 EISSN: 0972-2823 Vol. 56, Num. 4, 2010, pp. 281-283

Journal of Postgraduate Medicine, Vol. 56, No. 4, October-December, 2010, pp. 281-283

Case Report

Pituitary adenoma and vestibular schwannoma: Case report and review of the literature

Y Niu, L Ma, Q Mao, L Wu, J Chen

Department of Neurosurgery, West China Hospital, Sichuan University, Chengdu, Sichuan Province, China

Correspondence Address: J Chen, Department of Neurosurgery, West China Hospital, Sichuan University, Chengdu, Sichuan Province, China, jchen6811@tom.com

Date of Submission: 02-Mar-2010
Date of Decision: 28-Mar-2010
Date of Acceptance: 10-Jun-2010

Code Number: jp10082

PMID: 20935399

DOI: 10.4103/0022-3859.70940

Abstract

Keywords: Acoustic neuroma, field cancerization, multiple primary tumors, pituitary adenoma, vestibular schwannoma

Introduction

The first case of multiple primary tumors (MPTs) was reported in 1882. Since then, there have been multiple reports of MPTs of the head and neck region, digestive tract, urinary tract and respiratory tract. They are classified into homeochronous and metachronous. Intracranial MPTs are much less frequent than others, especially homeochronous intracranial MPTs. A total of three cases of acoustic neuroma (AN) associated with pituitary adenoma were documented in the literature. The etiologic reason of MPTs is not clear, and several hypotheses have been proposed. Among them, the new field cancerization model is more consistent with the pathogenesis of this type of concurrent intracranial MPTs.

Case Report

A 42-year-old female presented with a history of weight gain and repeated dizziness of one year and tinnitus of one month. Her medical history and family history were insignificant. She presented with some typical manifestations of acromegaly including thick sound, large forehead, nasolabial hypertrophy, bilateral thick fingers, feet hypertrophy, and hypertension. Her vision was normal and there was sensorineural hearing loss in the left ear, while facial and lower cranial nerves were intact. Audiograms an also revealed severe hearing loss on the left. Blood test revealed an elevated somatotropic hormone of 29.27 nmol/L.

She underwent gadolinium-enhanced magnetic resonance imaging (Gd-MRI) of the brain, which revealed that the significantly increscent pituitary (1.6Χ1.6Χ1.6 cm) stick out of the diaphragma sellae (showing a "snowman" sign) and the pituitary unevenly enhanced on T1-weighted Gd-MRI [Figure - 1]a. Besides, there was an enhanced space-occupying lesion (2.2Χ2Χ1.9 cm) on the left cerebellopontine angle with evidence of brainstem compression and internal auditory canal expansion [Figure - 2] and [Figure - 3]a. Although no pathological examination was done on this case, the clinical symptoms and imaging features indicated a clear diagnosis of a pituitary adenoma combined with AN.

The lesion had adjoined the brainstem and optic chiasma and presented a very high operative risk to the brainstem or optic nerve. This had deterred the neurosurgeon from operating on this complex lesion. Therefore, a more conservative treatment of gamma-knife (GK) radiosurgery was performed instead. She underwent GK radiosurgery for AN on May 11, 2008, and for pituitary adenoma on May 20, 2008. The AN was covered with 50% isodose volume administered at four target points using one 18-mm and three 8-mm collimators and a central dose of 24Gy was used to obtain a marginal dose of 12 Gy. The pituitary adenoma was covered with the 50% isodose volume administered at eight target points using three 8-mm and five 4-mm collimators and a central dose of 50Gy was used to obtain a marginal dose of 25 Gy .

The surgery was successful and she was injected with "Somatuline". At six months follow-up, hearing in her left ear recovered and the audiograms revealed a normal audiometric curve. Somatotropic hormone in serum decreased to 9.27 nmol/L. In addition, the pituitary adenoma (1.6Χ1.6Χ0.5 cm) and AN (1.2Χ1.5Χ1.2 cm) were alleviated compared to previous findings [Figure - 1]b and [Figure - 3]b]. Follow-up results supported our diagnosis, although no pathological analysis was done.

Discussion

The majority of ANs originate in the auditory nerve schwann cells of the vestibular branch, while pituitary adenoma occurs in the pituitary gland. The concurrence of multiple primary brain tumors with different histological characteristics is rare. Only three such cases of AN associated with pituitary adenoma have been reported in the literature [Table - 1]. ^[1],[2],[3] We provide a brief description of the pathogenesis of our case which was not included in the previous three cases and discuss its clinical significance.

According to Warren and Gates, MPTs are defined as: (1) each tumor must present a definite picture of histopathology, (2) each must be distinct, and (3) the probability of one being a metastasis of the other must be excluded. ^[4] Most of the time, they occur in the head and neck region, digestive tract, and urinary system. ^[5],[6],[7] Although our case report had no histopathological diagnosis, clinical manifestations, imaging findings and follow-up results after GK radiosurgery all supported our diagnosis that the tumors had different histological characteristics, moreover, met the latter two above mentioned criteria indicating the concurrent presence of two types of intracranial tumors.

The etiology of MPTs is not clear. Slaughter et al.,[8] elaborated the theory of "field cancerization", and proposed that long-term carcinogenic exposure results in ′′condemned mucosa′′ containing many mutated cells, from which multifocal polyclonal tumors develop independently. In recent years, however, a monoclonal origin involving stem cells has been hypothesized. According to this theory, the field cancerization process can be divided into three phases, each with its own histological and molecular characteristics. In the initial phase, a stem cell acquires genetic alterations and forms a "patch". The conversion of a patch into an "expanding field" is the next critical step which requires additional genetic alterations. Years later and during the third phase, in an expanding field, clonal divergence can subsequently lead to the development of several different tumors. ^[9] Those genetic alterations may involve loss of heterozygosity, chromosomal changes, gene mutations, and epigenetic modifications, which can be detected by polymerase chain reaction-based microsatellite analysis, DNA sequencing, comparative genomic hybridization, and occasionally by immunohistochemistry. ^[10]

As summarized in [Table - 1], all four such cases of pituitary tumor were associated with left AN. Two of these four cases were growth hormone tumor, one was prolactinomas, and the other was non-functional adenoma. The field cancerization theory hypothesizes that pituitary tumor and AN are derived from a common progenitor clone due to various genetic events ultimately developing subclones in the left cerebellopontine angle and saddle area forming an "expanding field". Eventually, left AN and pituitary adenoma occur simultaneously or separately. And in the development of the malignant clone, broblastic growth factor receptor 1, a frequent molecular alteration both in AN and pituitary adenoma, may play a role. ^[11],[12] In addition, age, environmental carcinogens, immunosuppression, certain kinds of viral infection, and genetic predisposition are considered risk factors for MPTs. ^[13]

This model has important clinical implications: the detection and monitoring of "expanding fields" may help early detection of the development of a second field tumor and prediction of local relapse after treatment. When pituitary tumor or AN is detected separately, we might consider the development of a second eld tumor after oncological treatment, especially after radiotherapy. ^[14] Because the oncological treatment might activate the common progenitor clone which led to the development of second field tumor. But their incidence has not been perceived because most patients had a short life expectancy after treatment or their follow-up was shorter than 15 years. ^[15] Therefore, the complete understanding of this model may benefit us in preventing the second eld tumor occurring after oncological treatment.

References

Copyright 2010 - Journal of Postgraduate Medicine

The following images related to this document are available:

Photo images