Endolymphatic stromal myosis with focal tubular-glandular differentiation (biphasic endometrial stromal sarcoma)

A case of low grade endometrial stromal sarcoma with tubular-glandular differentiation is reported. The tumor showed a characteristic pattern of clusters and trabeculae of spindle-shaped cells infiltrating the myometrium. Lymphatic invasion was evident. Foci of solid, alveolar pattern and cleft tubular spaces were seen. The tubular spaces were lined by a cuboidal epithelium, which at the ultrastructural level showed blunt microvilli, and between adjacent cells junctional complexes and desmosomes. Both the spindle-shaped cells and the epithelial cells were rich in cytoplasmic filaments. The latter did not react with serum containing antibody against actin using a two-layer immunoperoxidase method. The ultrastructural resemblance between the epithelial and spindle-shaped cells favors a common cellular origin, the endometrial stromal fibroblast.