A cytochemical method of grading the malignancy of salivary gland tumours preoperatively.

Aspiration biopsy is an accurate but still a somewhat controversial method of diagnosing salivary gland tumours preoperatively. During the last few years this method has been more and more accepted dependent on its increasing reliability in diagnosing the different types of tumours, but for an adequate treatment it is also important to know the malignancy degree of the individual tumour. Since invasiveness is the most significant morphological criterion in evaluating the prognosis of a salivary gland tumour it has, however, been difficult to grade the malignancy morphologically on a cytological basis. Thus the diagnostic value of the aspiration biopsy method would increase, if beside the morphological determination of the tumour type it was possible to find a cellular criterion which reflects the grade of malignancy. In the present investigation we have studied the nuclear DNA content in non-invasive tumours and invasive tumours. In general, invasive tumours were characterized by a higher degree of abnormality with respect to the DNA content than the non-invasive tumours. In two tumour types especially studied-mucoepidermoid carcinoma and acinic cell carcinoma-the property of non-invasive growth was found to be associated with a diploid or near-diploid DNA content, whereas invasive growth was associated with a triploid or near-triploid DNA content. These data suggest that the nuclear DNA Content may be related to the morphological differentiation and particularly to the invasive properties of the salivary gland tumours. Thus, cytophotometric DNA analysis of DNA content in the smears from aspirates might be valuable in grading the malignancy of the tumours preoperatively by aspiration biopsy.