Rare Tumors of the Parapharyngeal Space

Myoepitheliomas are considered extremely rare neoplasms and they are usually located in the parotid gland or the minor salivary glands. The present paper describes the clinical, histopathological, and immunohistochemical features of two cases of myoepithelioma, which were located in the parapharyngeal space. Tumors of the parapharyngeal space are relatively rare and account for 0.5 to 0.8% of all head and neck tumors. Most primary parapharyngeal tumors are benign. Of these, 40 to 50% are of salivary gland origin, the majority of which are pleomorphic adenomas. Parapharyngeal tumors are located in the prestyloid compartment and can arise either from the minor salivary glands in the parapharyngeal space or from the deep parotid lobe. Deep lobe tumors of the parotid gland represent 12 to 25% of all parotid tumors. Parapharyngeal tumors are usually discovered late in their clinical course because of their obscure anatomical location and late onset of symptoms. Tumors must reach a size of 2.5 to 3 cm before either they become palpable as a parotid mass or they become visible on the lateral pharyngeal wall. Other signs and symptoms may include dysphagia, foreign body sensation, unilateral middle ear effusion, pulsatile tinnitus, otalgia, bruit, thrill, hoarseness, dyspnea, true vocal cord palsy, Horner's syndrome, and dysarthria. We recently conducted a retrospective study of the medical records and histopathology files of all parotid tumors operated at our hospital from January 1998 until January 2006. Out of a total of 272 cases, 213 patients (78.4%) had benign lesions and 59 patients (21.6%) had malignant lesions. Four (1.5%) of the 272 cases were myoepitheliomas and two of those cases originated in the deep parotid lobe. This report aims to highlight the importance of awareness of this rare tumor in the differential diagnosis of parotid neoplasms, considering the increasing number of relevant reports in the medical literature. We advocate caution in the evaluation of myoepitheliomas in order to avoid misdiagnosis, on the grounds that benign myoepitheliomas exhibit more aggressive features than initially believed and malignant myoepitheliomas definitely do not qualify as low-grade malignancies.