Endometrial stromal tumors with typical morphology usually do not pose diagnostic problems. However, the finding of unusual morphologic features may be misleading in the final interpretation of these tumors. Herein, we described two endometrial stromal sarcomas discovered in hysterectomy specimens of women 31 and 75 years of age. Features typical of endometrial stromal neoplasia were present in both cases. Additionally, in 1 case, extensive fatty metaplasia as well as smooth and skeletal muscle metaplasia were found; and in the second case, focal bizarre nuclei, smooth muscle differentiation, and fibrous change were present. The differential diagnosis in the first case included cellular intravenous leiomyomatosis/lipoleiomyomatosis with skeletal muscle differentiation; and in the second case, a cellular smooth muscle tumor with bizarre nuclei was considered.