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Abstract Background Endometrial carcinoma is molecularly categorized into four subgroups: polymerase-E exonuclease domain-mutant (POLE-mut), mismatch repair-deficient (MMR-d), p53-abnormal (p53-abn), and no specific molecular profile (NSMP). This classification scheme has been included into clinical recommendation for post-operative risk-based management, although there have been few Asian studies on this topic. The present study aimed to evaluate the prevalence and clinical outcomes of endometrial carcinoma using this classification in Northern Thailand and the feasibility of implementation in resource-limited settings. Methods Endometrial carcinomas from hysterectomy specimens were classified using immunohistochemistry for MMR proteins and p53, as well as POLE mutation testing. Clinicopathological variables and outcomes were analyzed. The costs of the molecular information-based approach were compared to those incurred by the conventional approach (without molecular classification). Results Of 138 patients, 52.9% in the NSMP subgroup, 28.2% were in the MMR-d, 13.8% in the p53-abn, and 5.1% in the POLE-mut. After adjusting for other variables, patients with POLE-mut showed the most favorable outcomes, while those with p53-abn had the poorest survival. When estimating the costs for post-operative management, the use of molecular classification resulted in a 10% increase over the conventional approach. However, the cost increased only by 1% if only POLE testing was used to identify patients for treatment omission. Conclusion In Northern Thailand, endometrial carcinoma had comparable subgroup distribution and prognostic implications to previous reports, supporting the implementation of management guidelines that incorporate molecular information. In resource-limited settings, at least POLE mutation testing in early-stage patients should be considered.

Placental mesenchymal dysplasia (PMD) is a rare disorder of the placenta characterized by placentomegaly with diffuse hydropic stem villous, aneurysmally dilated vessels, and lack of trophoblastic proliferation. Case: The prenatal ultrasound of a 34-year-old woman (G1P0) at 33 weeks of gestation showed an enlarged placenta with multiple cystic lesions, heterogeneous echoes with no active blood flow, and fetal growth restriction (FGR). The differential diagnosis involved partial mole, placental hemorrhage, and PMD. She developed preeclampsia at 38 weeks of gestation and gave birth to a normally formed, growth-restricted baby. The placenta, weighing 785 g, showed scattered cystic vesicles in the parenchyma. The histology shows enlarged edematous stem villi with occasional cistern formation and no area of chorioangioma or features of molar pregnancy. PMD associated fetal growth restriction was diagnosed. Conclusion: PMD has prenatal ultrasound result resembling those of partial mole, placental hemorrhage and chorioangioma, but the fetus is phenotypically normal. Nevertheless, fetal surveillance is essential.

The clear-cell variant of epithelioid mesothelioma is an extremely rare neoplasm of the peritoneum. It shares histomorphologic features overlapping with a wide variety of tumors including carcinomas and other non-epithelial neoplasms. The diagnosis of peritoneal clear-cell mesothelioma is not always straightforward, despite known immunohistochemistry (IHC) markers. Due to its rarity, this entity may be diagnostically confused with other clear-cell neoplasms, particularly in intraoperative frozen sections. Here, we present a case of clear-cell mesothelioma originating in the uterine serosa that was initially misdiagnosed as clear-cell adenocarcinoma in the intraoperative frozen section. Microscopically, the tumor showed diffuse tubulocystic spaces of variable size lined by clear cells with moderate nuclear atypia. Immunohistochemical staining confirmed the diagnosis of clear-cell mesothelioma. Recognition of this entity, albeit rare, is important as the diagnosis may significantly affect the management considerations. The judicious use of an IHC panel helps to distinguish this tumor from other mimickers.

Small cell carcinoma (SCC) of vagina is extremely rare. The association between this tumor and high-risk HPV infection is unclear. To our knowledge, HPV status has been reported in only 3 previous cases of SCC of vagina. Herein, we present a unique case of vaginal small cell carcinoma with discordant HPV testing results between vaginal and cervical samples. We also review and discuss findings from previously reported cases of small cell carcinoma of vagina.

Microcystic stromal tumor (MST) is a rare type of pure stromal tumor in the category of ovarian sex cord-stromal tumors. It is characterized by a distinctive microcystic appearance with bland tumor cells. Although the pathological diagnosis can be straightforward based on the typical histomorphology in most MSTs, the cases with morphologic variation can pose a diagnostic challenge due to unfamiliarity of pathologists with the histologic spectrum of MST and its negativity for inhibin and calretinin, the commonly used sex cord-stromal markers. The coexistence between MST and mucinous epithelial tumor is extremely rare. We present the first case, to our knowledge, of ovarian MST with predominant bizarre nuclei coexisting with mucinous cystadenoma in a pregnant woman. The histomorphology in this case presents a diagnostic challenge and raises differential diagnosis for a wide variety of ovarian malignant neoplasms including nonneoplastic lesions.

The occurrence of malignant transformation in mature cystic teratoma of the ovary is rare, with squamous cell carcinoma being the most common histologic type. Sarcomatous transformation has been rarely described in the literature. We present a case of leiomyosarcoma with a minor component of squamous cell carcinoma arising in mature cystic teratoma of ovary in a 65-year-old woman. The malignant tumor showed two distinct components of sarcomatous and invasive epithelial elements, which were confirmed by immunostaining. To our knowledge, only four cases of leiomyosarcoma in ovarian mature cystic teratoma have been reported and this is a unique case report of leiomyosarcoma and squamous cell carcinoma arising in a mature cystic teratoma of ovary.

Angiosarcoma of the ovary is rare but represents an aggressive type of malignant ovarian neoplasms. The purpose of this report is to describe the features of angiosarcoma arising in mucinous tumor that was misinterpreted as a benign vascular proliferation during the intraoperative consultation. A 45-year-old woman presented with an abdominal mass for 1 month. Exploratory laparotomy was performed. A 35 cm right ovarian mass submitted for intraoperative consultation was a multicystic mucinous tumor with an 8 cm area of hemorrhagic lesion between cystic locules. The frozen section diagnosis was at least mucinous borderline tumor. The hemorrhagic area, which was intraoperatively interpreted as organizing vessels associated with previous hemorrhage, represented angiosarcoma in permanent sections. Angiosarcoma may present a challenge in intraoperative frozen section diagnosis of an ovarian mass. The presence of ectatic anastomosing vessels with dissecting growth appears to be the clue to a suspicion of angiosarcoma. The presence of endothelial atypia provides further support for the diagnosis. A macroscopic hemorrhagic area in an ovarian mucinous tumor should be evaluated with care, and the possibility of angiosarcoma should be borne in mind.