Carcinoma ex-pleomorphic adenoma of mandible: A case report and review of literature.

Introduction And Importance: The most common benign neoplasm of major and minor salivary glands is pleomorphic adenoma (PA). Around 80 % of all parotid neoplasms are pleomorphic adenomas, while 44-68 % and 38-43 % tumors were pleomorphic adenomas of submandibular and minor salivary gland tumors. PA has been reported in a variety of anatomic locations including true intraosseous mandibular tumor, external ear canal, TMJ region, lacrimal gland, epiglottis, larynx and nasopharynx, breast, lung, esophagus, sinonasal and skull base and trachea. Pleomorphic adenoma has a tendency to transform into a number of malignancies; carcinoma ex-pleomorphic adenoma, carcinosarcoma or metastasizing pleomorphic adenoma. Pleomorphic adenomas most commonly transform into carcinoma ex-pleomorphic adenoma (CEPA).

Case Presentation: A 30-year-old male presented with the primary complaint of a long-standing swelling at his right mandibular region for past 18 months. On intra oral examination, there was a non-healing alveolar socket of right lower 3rd molar tooth while rest of the dentition and mucosal surfaces were normal. On extra oral examination, mouth opening was adequate with intact lower border of the mandible and no palpable lymph nodes in the neck. Initial biopsy of lesion showed pleomorphic adenoma, but later the lesion came out to be carcinoma ex-pleomorphic adenoma, for which he underwent segmental mandibulectomy and free fibular flap.

Clinical Discussion: The prevalence of CEPA transformation from pleomorphic adenoma is 1.5 % within the first 5 years of diagnosis, going up to 10 % after 15 years. The true rate of malignant transformation in recurrent pleomorphic adenoma is reported to be 3.3 %. We report a case of an intra-osseous carcinoma ex pleomorphic adenoma (CEPA) of the mandible. It is thought that ectopic entrapment of salivary tissue or developmentally included embryonic remnants of submandibular glands within recesses or lacunae of the mandibular bone could explain the intraosseous origin of a salivary gland tumor in the mandible. Since carcinoma ex pleomorphic adenoma (CEPA) arises from primary or recurrent pleomorphic adenoma, therefore it poses a diagnostic challenge for histopathologists. The radiographic picture of primary tumor/recurrence can mimic odontogenic cyst/tumor; therefore, a sinister disease process should always be kept in mind. In the post operative period, regular follow up is required to treat any recurrence. The recurrence rate for such disease has not been documented.

Conclusion: Intra osseous CEPA is a very rare tumor. Intra bony tumors which rapidly increase in size have signs and symptoms of nerve involvement and cause bony destruction should have a high suspicion of index of malignancy. Therefore, biopsy must be correlated with clinical and radiological features. Regular follow up is necessary to detect any recurrence promptly.