[Subcutaneous myolipoma with bizarre cells: morphological, immunohistochemical and ultrastructural study of a case and review of the literature].

A new case of subcutaneous myolipoma is reported. Grossly it appeared as a yellow-whitish nodule of 5.5 cm, in its major axis and showed well defined borders. Histologically the tumour was constituted by two components: areas of mature fat tissue were interminged with more cellular areas composed of bundles of spindle shaped eosinophilic cells, reminiscent of smooth muscle cells. In these latter component, cells showing multilobated, bizarre nuclei were also focally evident. No areas of necrosis, nor mitosis were found in both the components of the lesion. The immunohistochemical and ultrastructural findings revealed the myofibroblastic nature of the cellular myoid component of the lesion. The presence of myoid cells with bizarre, multilobated nuclei was considered expression of a regressive phenomenon, as observed in the so called "bizarre" leiomyoma of the uterus. Two years after the initial diagnosis the patient is well and free of disease. Soft tissue myolipoma is a benign lesion which has to be distinguished from lesions with malignant or uncertain biologic behaviour. The clinicopathologic features of the present case are discussed and compared to those of the previously reported cases of soft tissue myolipoma.