INCIDENCE AND PROGNOSIS OF MINOR SALIVARY -GLAND TUMORS

Tumours of the minor salivary glands are rare. Reports in the literatu re on incidence, histological types, therapeutic modalities, relative cure rates and outcome are controversial. 580 patients with salivary g land tumours of epithelial origin were treated at the Department of Ot orhinolaryngology, University of Cologne, Germany, during the 28-year period from 1965 to 1992. 85 (14,7%) of these originated in the minor salivary glands. 41 of them were malignant, with a marked predominance of adenoid cystic cancer (ACC) (29/41, i.e. 71%). Minor salivary glan d tumours are found equally often at the palate, at other oral sites a nd in the nose and paranasal sinuses. They are rare in the larynx, pha rynx and trachea. Whereas only 32% of those tumours originating from t he hard palate were malignant, 55 % of those originating from other or al locations and 88% of those at other sites (mainly nasal cavity and paranasal sinuses) demonstrated malignant growth. 39% of these were st aged T1/T2 and 61% T3/T4 on admission. The average pre-treatment sympt omatic interval was 2 years. Response to surgical and additional radio logical therapy in advanced stages and survival demonstrated better re sults as opposed to patients after treatment of malignant parotid glan d tumours, if identical stages of the disease were compared. However, the percentage of advanced stages was significantly higher in minor sa livary gland tumours as opposed to parotid gland tumours. 82% of 11 pa tients with T1/T2 ACC of the minor salivary glandS survived free of re currence (median follow-up 11.4 years), while only 36% of 17 patients with T3/T4 ACC had disease-free survival for a median follow-up of 10 years. One patient was lost to follow-up. Of 4722 minor salivary gland tumours found in the literature, 50.3% were malignant. The rate of ma lignant tumours in minor salivary glands is thus more than double the rate of malignant parotid gland tumours. Location at the palate indica tes lower malignancy rates and earlier discovery of the tumour, while location in the nose and paranasal sinuses indicates a 93.6% malignanc y rate and poor prognosis due to frequently more advanced tumour growt h at this location. The size of the primary tumour is the single most important prognostic factor. There is no standardised therapy for mino r salivary gland tumours to date, but radical surgical resection with postoperative radiotherapy has been reported to offer best cure rates. Selective intraarterial cytotoxic therapy has been reported to be eff ective in the treatment of ACC of the minor salivary glands and may co ntribute to better local control and survival rates in the future.