Three cases (two ovarian and one retroperitoneal) of mucinous tumors with solid nodules are reported. The predominant picture in the three cases was that of a mucinous cystic tumor, but small nodules of solid anaplastic carcinoma were found in all three cases. In addition, one case showed microscopic foci of microcyst rupture with histiocytic response reminiscent of sarcoma-like mural nodules, one case showed several sarcoma-like nodules, and one case showed apparent transition from anaplastic carcinoma to spindle cell sarcoma. Histologic and immunohistochemical characteristics of the lesions are given, as differentiation of these nodules is important.