Primary squamous cell carcinoma of the parotid gland: the importance of correct histological diagnosis.

BACKGROUND: Primary squamous cell carcinoma of the parotid is an uncommon, aggressive malignancy with a poor prognosis. The diagnosis is made after excluding metastasis from other sites in the head and neck or other primary malignancies of the parotid.
METHODS: Tumor registry data from 1974 to 1994 were reviewed at three University of Louisville-affiliated hospitals. Of 370 parotid tumors, 40 (11%) were initially classified as squamous cell carcinoma of the parotid. Chart review and histological specimen re-examination were conducted to confirm diagnosis.
RESULTS: Only 8 (2%) of the 370 cases, were considered true primary squamous cell carcinoma of the parotid. Patients with metastases to the parotid from primary sites within the upper aerodigestive tract or skin of the head and neck region and high-grade mucoepidermoid carcinoma of the parotid were excluded. Facial nerve dysfunction was a presenting complaint in three patients. Two patients presented with American Joint Committee on Cancer (AJC) clinical stage III disease and six with AJC stage IV disease. All patients were treated with total parotidectomy and radiotherapy. One patient (12%) is alive and free of disease. Median survival was 13 months (range, 11 months-7 years).
CONCLUSIONS: Primary squamous cell carcinoma of the parotid is uncommon, occurring in 2% of parotid neoplasms at our institution. This is an aggressive malignancy, usually presenting in advanced stage and with facial nerve involvement or cervical metastases. Prognosis is poor even with radical surgery and adjunctive radiotherapy. Careful clinical and histological review is necessary to differentiate primary squamous cancer of the parotid from metastases or other primary parotid malignancy.