Clinicopathologic study of parapharyngeal tumors.

BACKGROUND: Parapharyngeal space (PPS) tumors are rare. Three main groups are identified, namely those of salivary origin, neurogenic tumors and paragangliomas. Early pathological classification of PPS tumors is important for pin point diagnosis and timely management. AIMS: The PPS is a complex anatomical potential space and poses high risk of per and postoperative complication. This study was done to perform optimum preoperative evaluation by clinicoradiologic correlation and guided fine needle aspiration cytology (FNAC) which is essential to minimize intraoperative risk.
MATERIALS AND METHODS: Guided FNAC was carried out to diagnose parapharyngeal tumors in 48 patients from January 2008 to January 2010. The inflammatory lesions were excluded in the present study. Correlation with histopathology was done in all the cases.
RESULTS: The mean age for all the patients was 38.2 years. There were 23 male and 25 female subjects. Seventy nine percent of the lesions were benign with pleomorphic salivary adenoma being the commonest, while only 20.8% of the lesions were malignant. All the patients presented with neck swelling. No complication was encountered in the present study.
CONCLUSION: FNAC can replace incisional biopsy which may be hazardous in this area. Immediate treatment can be planned based on the FNAC report.

Introduction

Parapharyngeal space (PPS) tumors are rare representing only 0.5% of head and neck neoplasms.[1] They often pose therapeutic and diagnostic problems due to variable non-specific symptoms and complex anatomy of the region. Most of the lesions of this region are benign in nature, with salivary gland neoplasm being the commonest followed by neurogenic tumors and paraganglioma in descending order of importance.[1] Apart from these, angiofibroma, ameloblastoma, sarcoma, meningioma, chordoma, branchial cleft cyst, hemangioma and lipoma are also encountered.[23] Because the PPS tumors are located deep within the neck, clinical examination and palpation are limited and unreliable.[4] With the advent of cross-sectional imaging studies incorporated along with guided fine needle aspiration cytology (FNAC), interpretation of the nature of these PPS lesions have definitely proved to be of much help.[5] Although histopathology remains the gold standard, owing to the difficult surgical approach of tumors in this region, guided FNAC has proved to be useful both in terms of morphological analysis and efficacy in terms of cost and time. When lesions are palpable in the retromandibular or submandibular area or transorally, FNAC may aid in surgical and postoperative planning.[6]

Materials and Methods

This is a prospective study conducted in a teaching hospital during January 2008 to January 2010. Forty eight patients who presented with PPS tumors as confirmed by radiology were included in the study. As part of history elicitation and physical examination, emphasis was made on the presenting symptoms and signs. Computed tomography (CT)-guided FNAC was performed in all the cases and a cytologic diagnosis was made. In cases where exact diagnosis could not be made on cytology, the lesions were categorized under the following headings:

Nature - Benign/Malignant.

Origin - Epithelial/Lymphoid/Mesenchymal

Primary or Secondary

Aspiration was done using 22 gauge disposable lumbar puncture needle and smears were stained by hematoxylin and eosin (wet smears) and May-Grünwald-Giemsa (dry smears). Confirmation was done by histopathology in all the cases and immunohistochemistry in selected cases.

Results

The total number of patients were 48. There were 23 male and 25 female patients. Out of these, 38 (79.1%) were benign, while only 10 (20.8%) were malignant. The mean age was 38.2 years. Table 1 shows the main presenting symptoms and Table 2 shows the main presenting signs. Table 3 shows the correlation between the cytologic and histologic diagnosis.

Table 1

Presenting symptoms

Table 2

Presenting signs

Table 3

Correlation of cytopathology with histopathology

Pleomorphic salivary adenoma (PSA) was the most common benign tumor encountered. From the two histologically confirmed cases of schwannoma, one case was diagnosed as benign spindle cell neoplasm and one as neurofibroma on cytology which was later confirmed by histopathology. One case of carcinoma ex-pleomorphic adenoma [Figure 1] was interpreted as adenocarcinoma of salivary gland origin. One case of metastatic nasopharyngeal carcinoma was diagnosed as non Hodgkin's lymphoma. The diagnosis was confirmed on biopsy material using immunohistochemistry for pan cytokeratin and leucocyte common antigen (LCA). Repeated aspiration yielded only blood in two cases of angiofibroma where histopathology came to the rescue.

Figure 1

Carcinoma ex-pleomorphic adenoma, the epithelial cell cluster to the right shows prominent nuclear atypia; fragments in the left is of benign spindle cells with a fragment of myxoid stroma (H and E, ×400)

Discussion

PPS tumors are difficult to diagnose early due to their location and plethora of presentation.[3] CT scan and FNAC have a great role in making the diagnosis and deciding the suitable surgical approach.[2] CT scan can demonstrate the exact size and extent of the tumor and its relationship to surrounding structure.[5] Magnetic resonance imaging (MRI) has also become a very useful diagnostic tool.

Salivary gland tumors comprise the majority of PPS tumors followed by neurogenic tumors and paragangliomas.[17] PSA arising from the deep lobe of parotid has been found to be the most common tumor of parapharyngeal region by several authors[7] and so it was in our study. Studies have shown that there is no difference in the prognosis of pleomorphic adenomas even if they are cellular and show cytologic atypia in the form of scattered hyperchromatic nuclei.[8] We had only one case of adenoid cystic carcinoma (2%) which has been found to be the commonest malignant tumor of minor salivary gland origin by Spiro et al.[9] Cellular PSA may resemble adenoid cystic carcinoma in smears. However, fragments of chondromyxoid matrix incorporating spindle cells are specific to pleomorphic adenoma.

Shoss et al.[10] presented the combined data from four studies representing 213 patients and showed that neurogenic tumors may account for more PPS lesions than traditionally thought. Schwannomas account for 20% of all PPS tumor and 20 to 40% of all schwannoma occur in the head and neck region.[11] However, in our study, we had only three cases of neurofibroma (6.25%) and two cases of schwannoma (4.1%).

Paragangliomas occurring in head and neck region comprise 3% of all paragangliomas and almost all are located in the PPS and arise in carotid body.[12] Carotid body paraganglioma can also be differentiated from cervical lymphadenopathy as they are fixed to the carotid bifurcation, so cephalocaudal mobility is restricted. We had one case of paraganglioma which was diagnosed on cytology and later on confirmed by histopathology and immunohistochemistry of the excised mass. The smears show follicular arrangement of cells with anisokaryosis but a bland nuclear chromatin. The PPS is the first site of metastases from nasopharynx, nasal cavity, palate and maxillary sinus.[13]

In our study, we found four cases of metastatic nasopharyngeal carcinoma and one case of metastatic squamous-cell carcinoma. Angiofibroma can also arise in this site.[14] However, in our two cases of angiofibroma, the cellular yield was very poor, one case yielded only blood and in the second case only a few benign spindle cells were present precluding a definite cytologic diagnosis. Distinction of lymphomas from carcinomas and other cancers of the head and neck are critical in designing treatment. There are no pathognomonic radiological features of PPS lymphoma; however, imaging is useful in excluding other common tumors of the PPS.[15] Primary malignant lymphomas of the PPS are rare and are predominantly B cell origin and only 11% are low grade.[15]

In our study, the single case of carcinoma ex-pleomorphic adenoma presented with facial palsy. Kenneth et al.[16] from Mayo clinic reported that neck mass or intraoral mass was the most common symptom initially. So was in our case. Lang[17] found that IX, X and XI cranial nerve palsies were common in the paragangliomas and malignant tumor, but not in the other tumors. A dual population of malignant epithelial cells and benign cells and stromal components of pleomorphic adenoma should arouse suspicion of carcinoma ex-pleomorphic adenoma.

Evaluation of PPS tumors is mostly radiographic with CT scanning and MRI offering useful diagnostic information.[18] Appropriate diagnosis can be reached radiographically in 95% of patients without tissue biopsy.[19] In our study, imaging modalities in combination with FNAC were diagnostic in most of the patient. In cases where the above failed, histopathology and immunohistochemistry were confirmatory.

Surgical extirpation remains the treatment of choice in PPS tumors.[20] In our study, there was no postoperative mortality and the patients are under follow up.

Conclusion

FNAC along with clinicoradiological correlation can prove to be an indispensable tool for diagnosing most of the PPS tumors, both benign and malignant, except for a few cases where histopathological examination is necessary. It can also have a great role in deciding the surgical approach to these tumors.