The nuclear DNA content and nuclear area of 22 jaw cysts, 15 benign and 40 malignant tumors and 4 other or unknown lesions of the oral cavity were measured with smear preparations stained with Feulgen reaction to study the characteristics of these lesions and to evaluate their diagnostic value as well as the relationship to the clinical course and histology. The nuclear DNA histograms of normal cells were all included in Type I with the modal peak at 2Cand there were no cells having DNA over 4

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... . The histogram pattern of the jaw cysts was similar to that of normal cells in most cases, but the histogram of odontogenic keratocysts with a slight subpeak at 4 C (Type II) or with an increased 3 C peak (Type IV) seemed to indicate the neoplastic nature of the cyst. In most benign tumors, the histogram pattern was either Type II or Type III with the modal peak located in the regions from 1. 5 C to 2.5 C. The presence of chromosomal changes, however, was indicated by the increase of the 3 C peak and by the occurrence of a distinct peak at 4 C or of cells with higher DNA content. The histograms of epidermoid carcinomas, undifferentiated carcinomas and a malignant melanoma were characterized by a broad distribution with no evident modal peak or its shift to the right. Excepting a few cases, such features were not evident in carcinomas of the salivary glands. The nuclear area was relatively small in the latter lesions, in particular in adenoid cystic carcinoma. In contrast to epidermoid carcinomas, there were many carcinomas of glandular origin that could not be diagnosed as malignant because of the similarity in the DNA histogram pattern to that of benign tumors. The results indicated the presence of low malignant type in salivary gland carcinoma. In these carcinomas, the increase of 3 C peak could be related to the occurrence of metastasis, T staging and prognosis, whereas in epidermoid carcinomas, no relationship was found between the T staging or prognosis and the DNA content that was increased in cases with metastasis. Histologically, the DNA content and nuclear area were increased in carcinomas of poor differentiation or those with higher nuclear atypia.