Ovarian myxoma. A study of two cases with long-term follow-up. Two cases of the so-called ovarian myxoma are reported. One was from a 13-year-old girl who had a 31-year follow-up and no evidence of recurrence. The second case, from a 65-year-old woman, recurred intraperitoneally, 19 years after the surgery. Both tumors were myxoid, with round to stellate cells. Immunohistochemical, electron microscopic (EM), and DNA flow cytometric (FCM) studies were performed on formalin-fixed, paraffin-embedded tissue of the second patient on both the primary tumor and the recurrence. Tumor cells expressed vimentin and were focally positive for desmin and myoglobin. EM findings suggested a fibroblastic differentiation. An aneuploid cell population was present in the recurrent tumor by DNA-FCM studies. Only four other cases of so-called ovarian myxoma were reported to date, and the follow-up does not exceed 18 months. The authors conclude that the presence of aneuploidy and the late recurrence of one of their cases suggest that certain ovarian myxomas might behave like low-grade sarcomas. The histogenesis of this tumor remains unsettled, but similarities were found with myxomas in other locations. 