Adenomyoma With Pseudoinvasive Growth Pattern and Serosal Penetration Mimicking Endometrial Carcinoma

We present a novel case of a 48-yr-old female with a uterine adenomyoma with an unusual pseudoinvasive growth pattern displaying full-thickness penetration beyond the serosal surface in association with a dehisced Caesarian scar. Before hysterectomy, magnetic resonance imaging findings showed an infiltrative lesion suggestive of endometrial carcinoma. An endometrial biopsy was benign but definitive operative management was pursued given the concerning imaging. Gross examination of the uterus demonstrated a 7.2 cm, relatively well-circumscribed polypoid neoplasm with pushing borders extending through the full thickness of the myometrium. A serosal defect with protruding red tissue was noted where the neoplasm penetrated the exterior surface of the uterus. Histologic examination demonstrated benign endometrial glands, associated endometrial stroma, thick-walled vessels, and a prominent smooth muscle component consistent with an adenomyoma. To our knowledge, this unique presentation of a pseudoinvasive adenomyoma extending beyond the serosa is extremely rare and is the first time reported in the literature.