HISTOLOGICAL GRADE CHANGE IN LOCALLY RECURRENT SOFT TISSUE SARCOMAS

Abstract

The unusual phenomenon of histological grade change in locally recurrent soft tissue sarcomas is examined by retrospective review of a large sarcoma database. Increased histological grade was found to occur in 20% of recurrent tumours. Several possible factors predisposing to grade change were examined, and only the histologic diagnosis of myxoid malignant fibrous histiocytoma was found to be significant. Despite increased histologic grade, these tumours do not appear to have a worse prognosis in terms of developing systemic disease.

Soft tissue sarcomas (STS) have a reported local recurrence rate of between five and thirty percent. Recurrent tumours are often similar histologically to the initial tumour, however they are occasionally of higher histological grade than the original lesion. Factors that predispose to this change in grade are not known.

We sought to identify the frequency at which locally recurrent STS demonstrate a change in histological grade, and to investigate the possible factors leading to this change. We also investigate whether a change in grade is associated with a poorer prognosis.

We identified one hundred and seventy-three patients who developed locally recurrent STS, one hundred and twenty-four of which met inclusion criteria and who will form the basis of this study. Ninety-two patients (74%) had no change in histological grade, twenty-four (19%) demonstrated an increase in histological grade and eight (7%) a decreased histological grade. Univariate analysis of time to local recurrence, histological diagnosis and use of radiotherapy and chemotherapy did not reveal significant differences between the groups who did and did not undergo change in grade. When the diagnosis of myxoid MFH was looked at separately, there was a higher proportion in the group that developed increased histological grade. Development of a change in grade was not associated with a poorer survival rate.

Increase in histological grade occurs in approximately 20% of locally recurrent STS, but this phenomenon is not associated with a poorer prognosis than if the grade remains the same. A histological diagnosis of myxoid MFH predicts for an increase in histological grade.