Minichromosome maintenance protein in myxofibrosarcoma

Abstract

Histopathological assessment of myxofibrosarcoma may be difficult, especially on the basis of a small core biopsy, which enables only a crude evaluation of grade and prognosis. Hypothesis - that determination of cell cycle state may assist in the diagnostic assessment of myxofibrosarcoma. 51 cases of high-grade (n=20), intermediate-grade (n=21), and low-grade (n=10) myxofibrosarcomas were studied, as well as nine cases of benign myxoma. Cell cycle state within tumors was determined by immunostaining for the recently described marker minichromosome maintenance protein 2 (MCM2), together with Ki67. Labelling indices for both markers were correlated with tumor grade, mitotic index, and time to first recurrence. The MCM2 labelling indices were significantly higher than the Ki-67 labelling indices. Both indices showed a significant correlation with the mitotic index and both showed significant increases with increasing grade of myxofibrosarcoma. The MCM2 labelling index (but not the Ki67 labelling index) showed a significant inverse exponential correlation with the time to first recurrence. Myxoid and cellular areas showed no difference in the MCM2 and Ki-67 labeling index, suggesting that clinically useful information could be obtained from any component of a myxofibrosarcoma sampled in a needle biopsy and/or cytological specimen. We therefore suggest that assessment of cell cycle state may be a useful diagnostic adjunct in the histopathological assessment of myxofibrosarcoma, by enabling more accurate determination of grade and prediction of outcome.