[Myoepithelial carcinoma ex-pleomorphic adenoma of the parotid gland].

INTRODUCTION

Myoepithelial carcinoma accounts for less than 1% of salivary gland malignant tumors. It may develop de novo or, in approximately 50% of the cases, from a pleomorphic adenoma.

OBSERVATION: A 57-year-old man with a history of a pleomorphic adenoma of the parotid treated surgically 6 years earlier, presented with a 2 cm tumor mass, palpable in the scar region. The histological examination and immunohistochemical study revealed a low-grade myoepithelial carcinoma. The patient had no complementary treatment. He presented 5 years later with a 2 cm parapharyngeal recurrence which was resected. There was no evidence of recurrent tumor or of distant metastasis at 4 year follow-up.

DISCUSSION: Although myoepithelial cells are often predominant in pleomorphic adenomas, carcinomas developing in pleomorphic adenomas show in most cases a glandular differentiation and myoepithelial carcinomas are rare. Currently the diagnostic criteria, the prognosis, and the management of myoepithelial carcinomas are not well documented. Invasive carcinomas developing in pleomorphic adenoma are known to be highly aggressive neoplasms and myoepithelial carcinomas ex-pleomorphic adenoma seem to have a better prognosis. Our reported case was characterized by the weak aggressiveness of the lesion.