Uterine Adenomatoid Tumor: A Great Imitator of Leiomyoma under Laparoscopy

A 31-year-old, nulligravid female with painful menorrhagia received a sonographic examination that displayed a 3.3 cm × 2.7 cm solid mass on her uterus [Figure 1]. Subsequent laparoscopic surgery revealed a well-circumscribed mass, which resembled a subserosal uterine leiomyoma,[1] that tightly adhered to the surrounding tissue and without a pseudocapsule [Figure 2]. Pathological examination disclosed branching pseudoglandular spaces lined by a single layer of flattened cells that demonstrated no mitotic activity or cytologic atypia [Figure 3a]. Calretinin staining with immunohistochemistry confirmed the diagnosis of uterine adenomatoid tumor (UAT) that originated from the mesothelium [Figure 3b].Figure 1: Under transvaginal ultrasonography, the circular-shaped tumor at the anterior wall of the uterus has a hyperechogenic center surrounded by a hypoechogenic rim (orange arrows)Figure 2: With laparoscopy, gross features of the uterine tumor resembled a International Federation of Gynecology and Obstetrics (FIGO) type 6 leiomyomaFigure 3: (a) Hematoxylin and eosin staining of the specimen revealed diffuse, cystic branching of pseudoglands covered by a single layer of linear cells (yellow arrows). (b) Under immunohistochemical staining, these linear cells were all positive for calretinin (brown), which suggested that they originated from mesothelial cells and confirmed the diagnosis of uterine adenomatoid tumor (×200, scale bar = 100 μm)UAT is a benign uterine lesion of mesothelial cells that often resides within the myometrium under the serosal layer or near the cornua, with incidence reported to be between 0.1% and 1%.[2] Shaped in a circular or oval dimension, it is usually <4 cm.[2] Although UAT characteristically presents a picture of hyperechogenic center surrounded by a hypoechogenic rim in ultrasonography, it is commonly misidentified as other uterine tumors during preoperative evaluations.[3] UAT can be diagnosed based on its microscopic features, such as interlacing pseudoglands, adenoid lesions, or angiomatoid structures lined by a single layer of mesothelial cells.[3,4] Occasionally, its irregular hyalinized connective tissue and tubular formations may be mistaken for malignancies.[5] Positive immunohistochemical staining for calretinin, WT-1, HBME-1, and D2-40 and negative staining for CD31 and carcinoembryonic antigen can help distinguish it from other neoplasms and confirm its benign nature.[2] Although laparoscopic can be employed in cases indicated for surgical excision,[6] procedure of myomectomy or enucleation can be challenging due to its dense adhesion to the surrounding myometrium. Thus, improving our understanding of the typical features of UAT can enhance its diagnosis and management. Ethical approval and Declaration of patient consen Approval was obtained from the Institutional Review Board before the commencement of this study. The ethical committee of our institute approved this study (approval no.: 202300245B0). The IRB approves the waiver of the participants’ consent. Financial support and sponsorship Prof. Chih-Feng Yen, an editorial board member at Gynecology and Minimally Invasive Therapy, had no role in the peer review process of or decision to publish this article. The other authors declared no conflicts of interest in writing this paper. Conflicts of interest There are no conflicts of interest.