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Gestational trophoblastic diseases derived from the chorionic-type intermediate trophoblast include benign placental site nodule (PSN) and malignant epithelioid trophoblastic tumor (ETT). Among PSN, the WHO classification introduced a new entity named atypical placental site nodule (APSN), corresponding to an ETT precursor, for which the diagnostic criteria remain unclear, leading to a risk of over-diagnosis and difficulties in patient management. We retrospectively studied 8 PSN, 7 APSN and 8 ETT to better characterize this new entity. We performed an immunohistochemical analysis (p63, hPL, Cyclin E, and Ki67), a transcriptional analysis using the Nanostring method to quantify the expression of 760 genes involved in the main tumorigenesis pathways, and a RNA sequencing to identify fusion transcripts. The immunohistochemical analysis did not reveal any significant difference in Cyclin E expression between the three groups (p = 0.476), whereas the Ki67 index was significantly (p LPCAT1-TERT fusion transcripts previously reported in ETT. The transcriptomic analysis allowed robust clustering of ETT distinct from the APSN/PSN group but failed to distinguish APSN from PSN. Indeed, only seven genes were differentially-expressed between PSN and APSN samples, CCL19 upregulation and EPCAM downregulation were the most discriminating features of APSN. In contrast, 80 genes discriminated ETT from APSN, establishing a molecular signature for ETT. Gene set analysis identified significant enrichments in the DNA damage repair, immortality and stemness, and cell cycle signaling pathways when comparing ETT and APSN. These results suggested that APSN might not represent a distinct entity but rather a variant of PSN or a transitional stage between PSN and ETT. RNA sequencing and the transcriptional signature of ETT described herein could serve as triage for APSN from curettage or biopsy material, enabling the identification of the cases that need further clinical investigations.

p57 immunostaining is performed on hydropic products of conception to diagnose hydatidiform moles (HMs), which can progress to gestational trophoblastic neoplasia. Partial hydatidiform mole (PHM) and hydropic abortion (HA) display positive staining in stromal and cytotrophoblastic cells, whereas complete hydatidiform mole (CHM) is characterized by loss of p57 expression in both cell types. In some cases, an aberrant pattern is observed, called discordant p57 expression, with positive cytotrophoblast staining and negative stromal staining, or vice versa. The aim of this study was to describe the clinical, biological, and pathological characteristics of p57-discordant villi (p57DV) and other associated populations in cases of divergent p57 expression and to compare the evolutions of p57DV-associated and classic CHMs. Seventy cases of p57DV diagnosed by referent pathologists were divided into two groups, G1: p57DV ± non-CHM component (n = 22) and G2: p57DV + CHM component (n = 48). p57DV morphology was similar in the two groups. Observation of more than two populations and hybrid villi on p57 immunostaining were significantly more frequent in G2. The clinical, ultrasound, and biological presentations of p57DV-associated and classic CHMs were similar. The initial pathological diagnosis was more frequently incorrect, missing the CHM component, for the p57DV-associated CHMs. Molecular genotyping was informative in seven cases and identified as androgenetic/biparental mosaicism in four cases. These results show that p57DV are a diagnostic challenge for pathologists and that most are associated with a CHM component. However, the clinical management of p57DV-associated CHMs should be the same as that of classic CHMs.

Objectives: To evaluate the frequency of placental pathological lesions in Beckwith–Wiedemann syndrome (BWS), an overgrowth disorder that exhibits etiologic molecular heterogeneity and variable phenotypic expression. Materials and methods: The study included 60 BWS patients with a proven molecular diagnosis and a placental pathological examination. Placentomegaly, placental mesenchymal dysplasia (PMD), chorangioma/chorangiomatosis, and extravillous trophoblastic (EVT) cytomegaly were evaluated and their frequencies in the different molecular subgroups were compared. Immunohistochemistry and fluorescent in situ hybridization (FISH) were performed on EVT cytomegaly. Results: Placentomegaly was found in 70.9% of cases, PMD in 21.7%, chorangioma/chorangiomatosis in 23.3%, and EVT cytomegaly in 21.7%; there was no significant intergroup difference. EVT cytomegaly showed loss of p57 expression, increased Ki67 proliferating index, and polyploidy on FISH analysis. Conclusions: There was no genotype/epigenotype-phenotype correlation concerning placental lesions in BWS. Diffuse EVT cytomegaly with polyploidy may represent a placental finding suggestive of BWS.

Placental mesenchymal dysplasia (PMD) and complete hydatidiform mole (CHM) with a coexisting fetus are 2 rare placental abnormalities characterized by lacunar placenta and presence of an embryo on ultrasound examination. We report the case of a 34-yr-old woman referred at 32.6 weeks of gestation because of a multicystic placenta. A caesarean section was performed at 39.1 weeks of gestation giving birth to a 2905 g normal female infant. Pathological examination revealed macroscopic and microscopic morphological, and immunohistological features of PMD in the main placenta, and features of CHM in a separate placental mass. Fluorescent in situ hybridization and molecular genotyping analyses showed diandric diploidy in the CHM component and androgenetic/biparental mosaicism in the PMD component, confirming the association of PMD and CHM with a live infant. There was no progression to gestational trophoblastic neoplasia during follow-up for the mother, or any sign of Beckwith-Wiedemann syndrome or hepatic tumor in the child.

Gestational trophoblastic disease encompresses a group of interrelated diseases, following a pregnancy after a variable period of time. Hydatiform mole corresponds to premalignant disorders composed of villi with excess of paternal genetic material, with a malignant potential more important for complete mole than partial mole. Gestational trophoblastic neoplasia includes invasive mole, choriocarcinoma, placental site trophoblatic tumor and epithelioid trophoblastic tumor. Their histological diagnosis may be problematic on curettage material and needs to be correlated to serum hCG level and radiological findings. The use of chemotherapy has dramatically improved the prognosis of these lesions. All patients with this rare disease need to be registered in the national service for gestational trophoblastic disease (http://www.mole-chorio.com), which coordinates their management at the national level.

International audience; We report a case of an unusual chorangioma in a 26-year-old gravida 2, para 1 female. The clinical course was complicated by premature birth at 34weeks' gestation. The baby presented with congenital cardiac and renal malformations. The tumor was 11cm in size, separated from the main placental mass and exhibited atypical histologic characteristics such as fibromatous areas, high cellularity, nuclear atypia and high mitotic index. These histologic features must not be interpreted as malignancy

Gestational trophoblastic disease encompresses a group of interrelated diseases, following a pregnancy after a variable period of time. Hydatiform mole corresponds to premalignant disorders composed of villi with excess of paternal genetic material, with a malignant potential more important for complete mole than partial mole. Gestational trophoblastic neoplasia includes invasive mole, choriocarcinoma, placental site trophoblatic tumor and epithelioid trophoblastic tumor. Their histological diagnosis may be problematic on curettage material and needs to be correlated to serum hCG level and radiological findings. The use of chemotherapy has dramatically improved the prognosis of these lesions. All patients with this rare disease need to be registered in the national service for gestational trophoblastic disease (http://www.mole-chorio.com), which coordinates their management at the national level.