Adenomatoid Tumor of the Uterus: A Report of 6 Unusual Cases With Prominent Cysts Including 4 With Diffuse Myometrial Involvement, 4 With Uterine Serosal Involvement, and 2 Presenting in Curettage Specimens.

We evaluated the clinicopathologic features of 6 adenomatoid tumors of the uterus with unusual features. All the tumors differed grossly from the usual adenomatoid tumor, typically being ill-defined and occupying >50% of the myometrium, essentially replacing it in 4. The neoplasm extended to the endometrium in 2 cases and in one of these it formed an intracavitary mass; in both the tumor was first diagnosed in a curettage. In the other 4 cases, the adenomatoid tumor was discovered in a hysterectomy specimen performed for irregular vaginal bleeding (3 patients), and the finding of a pelvic mass on a computed tomography scan in a patient with right lower quadrant pain. The tumors extended to the uterine serosa in the form of small grape-like vesicles or cysts in 4 cases. All tumors contained the typical small often irregularly shaped spaces but also had prominent cysts. When cysts involved the serosa, the microscopic appearance mimicked that of peritoneal inclusion cysts. In one case with serosal involvement, a prominent papillary pattern was also present. The cysts were typically closely packed with minimal intervening stroma but were occasionally separated by conspicuous smooth muscle bundles. The stroma in one case was extensively hyalinized. Two tumors were focally infarcted. A striking, but minor, solid growth in which the tumor cells were arranged in tightly packed nests or interanastomosing cords and trabeculae was seen in 2 tumors. The unusual gross and microscopic features of these tumors can cause significant diagnostic difficulty and bring into the differential diagnosis entities that are usually not realistic considerations. The presentation of 2 tumors in a curettage specimen represents an unusual clinical aspect.