Uterine sarcomas are rare malignancies accounting for approximately 3% of all uterine cancers. Among them, uterine adenosarcomas account for 5-10% of uterine sarcomas [1]. First described by Clement and Scully in 1974 [2], uterine adenosarcomas are characterized by a biphasic histology comprising a benign epithelial component and a malignant stromal component. This rare gynecologic malignancy typically presents with nonspecific symptoms, and its optimal management is yet to be clearly defined. Herein, we report a rare case of uterine adenosarcoma in a premenopausal woman that was incidentally diagnosed after a hysterectomy.

A 44-year-old nulliparous woman was referred to our gynecology department with a presumptive diagnosis of large adenomyosis. Pelvic ultrasonography revealed an enlarged uterus with a total volume of approximately 1 L and an endometrial thickness of 2.74 cm (Fig. 1). An endometrial aspiration biopsy revealed endometrial tissue with focal glandular atypia and myometrial tissue with mild cellular atypia and a few mitotic figures. Subsequently, total laparoscopic hysterectomy with bilateral salpingectomy was performed, and the uterus was extracted vaginally using an endobag without spillage. Histologic examination revealed adenosarcoma, a biphasic tumor composed of a benign glandular component and a malignant stromal component. The glandular structures were lined with a single layer of bland-appearing cuboidal epithelial cells. The stromal component consisted of low-grade spindle cell sarcoma and exhibited frequent subepithelial and periglandular condensation. Mitotic activity averaged four mitotic figures per 10 high-power fields. No evidence of sarcomatous overgrowth or heterologous elements was identified throughout the tumor. In addition, there was no evidence of myometrial invasion (Fig. 2). Surgical resection margins were tumor-free, and no other significant pathological findings were noted. A peritoneal biopsy of the cul-de-sac revealed a glandular structure within the fibromuscular tissue, suggestive of endometriosis. Based on these findings, the tumor was staged as pT1a according to the pathologic staging criteria. For further staging and evaluation of residual disease, distant metastasis, and lymph node involvement, abdominopelvic and chest computed tomography (CT) and fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT) were performed. CT showed a small low-density lesion around the right vaginal stump without significant lymphadenopathy (Fig. 3). FDG-PET/CT revealed mild hypermetabolic activity at the vaginal stump, suggestive of postoperative inflammation, with no other abnormal uptake. The serum CA-125 level (16.6 U/mL) was within the normal range. Subsequent diagnostic laparoscopy revealed no grossly visible tumors or enlarged lymph nodes. Bilateral oophorectomy and multiple peritoneal biopsies were performed. Histopathological examination of both ovaries revealed benign follicular cysts and chronic inflammation with foreign body reaction in the periovarian tissues. Biopsy of the vaginal stump demonstrated chronic active inflammation with foreign body reaction, and multiple peritoneal biopsies showed similar findings. Cytological analysis of ascitic fluid yielded negative results for malignant cells. After a comprehensive staging evaluation, including reoperation, the final stage was adjudged to be IA. Accordingly, no adjuvant treatment was administered, and at the 6-month follow-up, no evidence of recurrence was observed.

Uterine adenosarcomas are rare, accounting for 5-10% of uterine sarcomas [1]. This malignancy predominantly occurs in postmenopausal women. However, a Surveillance, Epidemiology, and End Results Database analysis of 544 patients with adenosarcoma revealed that 51.5% were aged between 40 and 65 years [3]. The patient in the present case was a 44-year-old premenopausal woman. The most common symptom of uterine adenosarcoma is abnormal uterine bleeding, followed by pelvic pain and mass-related symptoms [1,3,4]. On magnetic resonance imaging (MRI), uterine adenosarcomas often demonstrate slightly high signal intensity on T2-weighted imaging and variable signal intensity on T1-weighted imaging, mimicking endometrial polyps or submucosal fibroids [5]. However, distinguishing between these two entities based on imaging remains challenging, especially in the early stages of the disease. MRI was not performed preoperatively on our patient. Most cases originate in the endometrium, although occurrences in the cervix, myometrium, and other gynecological organs have been reported, with the ovary being the second commonest site [4]. In the present case, we performed reoperation, including bilateral oophorectomy and multiple peritoneal biopsies, to detect potential malignant changes and reduce the risk of recurrence. Several reported cases of uterine adenosarcoma have been pathologically associated with endometriosis [6]. Additional risk factors include the use of tamoxifen and prior pelvic irradiation [3,7]. Our patient had endometriotic tissue in the pelvic peritoneum without any additional risk factors. Adenosarcomas typically have a low malignant potential, and their prognosis is generally favorable for early-stage disease [8]. Patients without sarcomatous overgrowth have a reported 5-year overall survival of 69.3-80.0% [9]. Other poor prognostic indicators include myometrial invasion, tumor necrosis, significant cellular atypia, high mitotic activity, and heterologous elements such as rhabdomyoblasts. Among these, sarcomatous overgrowth and myometrial invasion are considered the most critical prognostic markers [1]. The patient in the present case had no adverse prognostic factors. Although there is no consensus regarding the optimal management of uterine adenosarcoma, total hysterectomy (TH) with bilateral salpingo-oophorectomy (BSO) is generally recommended [3]. This was performed in the present case as well. Lymphadenectomy is not typically indicated because of the low incidence of lymphatic spread [1,3,4]. Owing to the limited evidence on the efficacy of adjuvant radiotherapy, its role remains uncertain. Furthermore, adjuvant chemotherapy is unlikely to provide any clinical benefit to patients without sarcomatous or myometrial invasion [4]. Therefore, in this case, no adjuvant therapy was administered and close postoperative surveillance was planned.

Uterine adenosarcoma is a rare malignancy with a generally favorable prognosis in early stages. In the absence of poor prognostic factors, such as sarcomatous overgrowth and myometrial invasion, TH with BSO followed by close surveillance appears to be an appropriate management strategy. Further studies are required to establish standardized treatment guidelines for this uncommon tumor (IRB No. 2025-06-006).