CD56 is used in gynecologic pathology, typically in the context of a neuroendocrine, sex cord or sex cord-like tumor. It has never been studied in uterine smooth muscle tumors, which can potentially enter their differential diagnosis, and thus CD56 positivity could potentially be a pitfall. Thus, the aim of this study was to explore its expression in this category of tumors. Seventy-eight uterine smooth muscle tumors, including 14 leiomyosarcomas, 46 leiomyomas and their variants, 14 smooth muscle tumors of uncertain malignant potential, and 4 intravenous leiomyomatoses were studied in regard to CD56 expression. Fifty-eight nearby myometria were also analyzed. Sixtyfive (83.4%) tumors showed CD56 expression. Nearby myometrium showed CD56 expression in 15 cases (25.9%). Staining ranged from 10% to 100% of tumor or myometrial cells (median 80% and 50%, respectively). Among the tumor types, leiomyoma with bizarre nuclei, had the lowest extensive expression (P = 0.01). Most uterine smooth muscle neoplasms express CD56; thus, it is not useful in attempting to discriminate from endometrial stromal or sex cord-like neoplasms.

Vascular pseudoinvasion or displacement of tumor or normal endometrial tissue is a potential pitfall in uterine pathology. The proposed mechanisms of this phenomenon are mostly associated with the uterine manipulator used during minimally invasive hysterectomies. The aim of this report is to describe vascular pseudoinvasion in a still unreported setting, that of a postendometrial ablation hysterectomy, and to provide a summary of studies dealing with artifactual or nonmalignant myometrial vessel involvement by normal or neoplastic endometrial tissue.