An interesting case of pituitary adenoma presenting as an invasive nasopharyngeal tumor.

Pituitary masses usually present as sellar masses with suprasellar or parasellar extension. However, in unusual cases pituitary tumors especially macroprolactinomas and nonfunctional adenomas can present with intranasal extension which can be misdiagnosed as nasal polyp or a primary invasive nasopharyngeal malignant tumor. The otolaryngologists should be familiar with this rare presentation of pituitary masses. Measurement of prolactin (PRL) is essential in cases of recalcitrant nasal polyps or rhinorrhea as it may change the management in such cases. Here we describe case of a patient with an invasive pituitary adenoma who had presented in the otorhinolaryngology department with a nasal obstruction and epistaxis. We have also reviewed 30 cases of pituitary adenoma with nasopharyngeal invasion published in past.

INTRODUCTION

Nasopharyngeal masses form a small fraction of cases presenting with nasal obstruction. Commonest cause of nasopharyngeal malignancy is classical and undifferentiated variety of nasopharyngeal carcinoma. Discovery of pituitary tissue in the form of a nasopharyngeal mass is an extremely rare occurrence for the otolaryngologist. A careful history focusing on subtle features of hypopituitarism, imaging of sella, and histopathological examination for neuroendocrine features plays key role in identifying such cases. Here we discuss a case of a pituitary adenoma with an unusual nasopharyngeal invasion.

CASE REPORT

A 47-years-old man presented in the otorhinolaryngology department with a 4 month history of chronic left sided nasal obstruction, periodic epistaxis along with pain and difficulty in opening left eye. He also complained of frontal headache. Patient suffered from diabetes mellitus since last 10 yrs and had proliferative diabetic retinopathy in right eye.

On examination, patient had frontal sinus tenderness. There was complete third nerve palsy on left side [Figure 1]. Other cranial nerves were not affected. There was no periorbital edema. Ocular examination on right side was normal. There was no blackish discoloration of nasal or palatal mucosa. There was no conductive deafness. Patient was provisionally suspected of having an invasive nasopharyngeal malignancy or rhino-ocular mucormycosis of paranasal sinuses. However, nasal endoscopy revealed sphenoid sinus filled with expansive firm tumor. Biopsy from the mass showed nests and cords of synaptophysin positive cells with uniformly looking nuclei accompanied with necrotic fibro connective tissue consistent with possibility of pituitary adenoma with extensive necrosis. In view of the histopathological diagnosis, magnetic resonance imaging (MRI) of sella was planned and endocrine consultation was done.

Figure 1

Patient with left sided ptosis

MRI revealed a heterogenous mass lesion in sphenoid sinus extending posteriorly in pituitary fossa with stalk displaced posteriorly and pituitary gland not separately discernible from the lesion. The fat plane between the pituitary gland and lesion was effaced [Figures 2–5]. Upon endocrine evaluation, the patient had evidence of anterior pituitary hypofunction in the form of weakness, easy fatigability, reduced libido, nausea, vomiting, and increased episodes of hypoglycemia. He denied of having polyuria. Thyroid stimulating hormone (TSH) was 0.213 μIU/ml (0.2-5.1μIU/ml) with a free thyroxine (T4) of 0.6 ng/dl (0.95-2.25 ng/dl). Cortisol measured at 8:00 am was 4.93 μg/dl (5-23 μg/dl). His prolactin (PRL) level measured in serial dilutions was 2.0 ng/ml (2.7-17.0 ng/ml). Luteinizing hormone (LH) and Follicle-stimulating hormone (FSH) levels were normal. Transnasal transsphenoidal surgery was planned after optimization of thyroid and adrenal status. Postoperatively hormone supplementation was continued. Histopathological examination confirmed the diagnosis of pituitary adenoma. On immunohistochemistry, the cells were positive for synaptophysin and negative for prolactin, Adrenocorticotropic hormone (ACTH), and growth hormone (GH) markers. So the diagnosis was consistent with chromophobe adenoma of pituitary.

Figure 2

Sagittal T2 weighted MRI sella view showing heterogenous mass infiltrating sella completely. Pituitary tissue is not separately discernible from the mass (green arrow)

Figure 5

Axial T1 weighted view with contrast showing heterogenous enhancement by the mass and some areas of non-enhancement suggestive of necrosis. There is no evidence of hemorrhage

Coronal view T2 weighted image showing mass infiltrating the sphenoid sinus completely (yellow arrow) with minimal suprasellar bulging. Optic chiasm is intact. Stalk is slightly shifted to right with normal thickness and enhancement. Parasellar spread is minimal

Axial view showing infiltration by the invasive pituitary adenoma into sphenoid sinus and posterior ethmoidal air cells bilaterally (red arrow)

DISCUSSION

This case highlights an unusual nasal presentation of pituitary adenoma. Up to 2% of pituitary tumors have an infrasellar extension[1] but very few of them erode the floor of sphenoid sinus to enter in nasopharynx and nasal cavity to present as a nasal polyp. Approximately 35 cases of nasopharyngeal invasion of pituitary adenomas have been reported. The initial cases of pituitary adenoma presenting as nasal polyp were identified by Boyd[1] and Sir Harvey Cushing in 1910 and 1912.[2] Most of the cases reported are chromophobe adenomas followed by few macroprolactinomas and one case of somatotroph and corticotroph adenoma [Table 1].[34]

Table 1

Cases of pituitary adenoma invading nasopharynx published in the past$

Diagnosis in case of a functional pituitary adenoma is not difficult as signs of PRL, GH or ACTH excess would be obvious. Clinical features of hypopituitarism, although more common with pituitary tumors, can be occasionally seen in cases of meningiomas, craniopharyngiomas, and chordomas infiltrating sella. Diagnosis becomes especially challenging in cases where a pituitary adenoma is nonfunctional and has an exclusive infrasellar spread when it would mimic a nasopharyngeal mass.

Rarely, an ectopic pituitary tissue is located in extracranial sites like sphenoid sinus, nasal cavity, and nasopharynx. In such cases, presence of a normal pituitary gland in sella can help to differentiate it from an adenoma arising from ectopic pituitary tissue.

Other intracranial tumors which have nasal invasion are meningiomas, chordomas, and rarely germinomas. The differential diagnosis of nasopharyngeal tumors with intracranial invasion includes nasal angiofibroma, sphenoid sinus mucocele, pharyngeal craniopharyngioma, olfactory neuroblastoma, giant cell tumor, and adenoma arising from ectopic pituitary tissue [Table 2].[5]

Table 2

Differential diagnosis of invasive nasopharyngeal masses involving base of the skull#

Histological examination is utmost essential for differentiating pituitary tissue from other tissues. Histologically, pituitary tissue can be identified by a typical endocrine growth pattern which consists of tumor cells arranged in packets, ribbons, or rosettes, with prominent delicate vascularized stroma and immunohistochemical showing of neuroendocrine markers, and pituitary hormones in the tumor cells. Differential diagnosis on histology includes small cell cancer, non-Hodgkin's lymphoma, and plasmacytoma.[6]

Due to low frequency of occurrence, there are no specific guidelines on management of pituitary adenomas with intranasal extension. Medical treatment is justified in cases of prolactinomas without cerebrospinal fluid (CSF) leak or other complications. However, in presence of complications like pituitary apoplexy, neurological deficit or intolerance to medications or in case of nonfunctional adenomas, the best approach is surgery as per review of existing literature. Either microscopic transsphenoidal or endoscopic transnasal may be used to treat with choice of therapy guided by surgeon's experience.

To conclude, pituitary adenomas with nasopharyngeal invasion even for being very rare occurrence should be a part of differential diagnosis of sinonasal masses. The diagnosis needs a collaborative work by an expert otolaryngologist, an experienced endocrinologist, a sound radiologist, and an astute pathologist. Detailed endocrine evaluation with special emphasis on features of hypopituitarism, PRL, GH or ACTH excess, cranial nerve involvement is mandatory. The impact of accurate preoperative diagnosis on management and follow up of such cases cannot be underestimated considering the vast difference between management of pituitary adenomas and nasopharyngeal tumors.