Histopathological and Immunohistochemical Analysis of Rare Parotid Tumours: A Case Series

Abstract

Malignant salivary gland tumours are rare representing only 2% of all head and neck malignancies. The most common malignant salivary gland tumour is mucoepidermoid carcinoma followed by adenoid cystic carcinoma while parotid is the most common site. But there are presence of other rare variants with diverse biological feature of maliganacy including Salivary Duct Carcinoma (SDC), basal cell adenocarcinoma, Carcinoma ex Pleomorphic Adenoma (CXPA), polymorphous adenocarcinoma which represent 1-5% of all salivary gland neoplasm. They typically are high-grade carcinomas with presence lymph nodal metastases. Hereby, author report 5 rare cases of parotid gland malignancy detected by histopathological examination along with confirmation by immunohistochemical examination. A 60-year-old and 65-year-old male diagnosed with salivary duct carcinoma of left parotid and right parotid respectively with ipsilateral cervical lymph node involvement but peripheral resection margins were free from tumour invasion. A 50-year-old female diagnosed with basal cell adenocarcinoma of left parotid with lymph node metastasis and resection margin was involved by the tumour. A 60-year-old male presented with recurrent swelling in left parotid region, diagnosed as carcinoma ex pleomorphic adenoma with lymph node involvement in a case of pleomorphic adenoma of parotid, reported previously. A 52-year-old male presented with right-sided parotid region swelling for last six months having Fine Needle Aspiration Cytology (FNAC) report of pleomorphic adenoma. Parotidectomy revealed diagnosis of polymorphous adenocarcinoma while surgical resection margins were free. Surgery is the main mode of treatment in these tumours. Involvement of resection margins, extraparotid extension, lymphovascular and perineural invasion along with lymph node metastasis are the common indicator for postoperative radiation therapy.