The relevance of the DNA index and proliferation rate in the grading of benign and malignant soft tissue tumors

Abstract

The relevance of the DNA index (DI) to malignancy grading and the relationships between mitotic score, Ki-67 score, and the proportion of cells in the G1-phase (G1PF) of the cell cycle, as proliferative indicators, were investigated in benign (n = 8) and malignant (n = 46) soft tissue sarcomas. Although DI was not found to be related to the histology of the sarcomas, it was associated with malignancy grade, i.e., 14%, 25%, 42%, and 86% of benign, Grade 1, Grade 2, and Grade 3, respectively had a DI greater than 1. The relevance of aneuploidy in benign tumors is discussed and the literature reviewed. A subgroup of the malignant tumors (n = 13) had both a low mitotic score and a low Ki-67 value. However, a distinct correlation between Ki-67 and the mitotic score could not be shown. For malignant tumours G1PF was related to DI, i.e., low G1PF occurred in tumors with diploid DNA content. Low Ki-67 scores were observed in 59% of diploid tumors and in 20% of aneuploid tumors. However, it appeared that G1PF and Ki-67 were not correlated. In conclusion, (1) benign and Grade 1 tumors were predominantly diploid with high G1PF and low Ki-67 values, (2) most of Grade 3 tumors were aneuploid (86%) with low G1PF and high Ki-67 values, and (3) the group of Grade 2 tumors could be divided into two subgroups either with the characteristics displayed by benign and Grade 1 tumors (DI = 1, low Ki-67 scores, and high G1PF) or with the characteristics exhibited by Grade 3 tumors (DI greater than 1, high Ki-67 scores, and low G1PF). Hence, supplementary to the grading of soft tissue tumors, DI, G1PF, and Ki-67 score could be useful as prognostic parameters in soft tissue tumors.