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case_images: CC pathology and 18F-FDG PET/CT images. (A and B) Clinical responses of the patient to DC+ICI treatment: PR. (C) HE-stained section of the tumor showed extensive hemorrhage and necrosis at low magnification, the biphasic feature of mixed cytotrophoblasts (black triangle) and syncytiotrophoblasts (black arrow) and nuclear division in tumor cells (star) at high magnification. In some regions, tumors are mainly composed of mononuclear cytotrophoblasts, and syncytiotrophoblasts are few and inconspicuous, which is easy to be misdiagnosed as poor-differentiated carcinoma. Immunohistochemical markers provided further support for the diagnosis of CC.
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case_images: PET/CT), which showed markedly enlarged oral and lung lesions with hypermetabolism, and no other specific abnormalities were found (Figure 1A). Pathological examination of the palatal mass revealed a tumour similar to a previous gingival mass in morphological and immunohistochemical (IHC) features, with massive tissue necrosis, atypical neoplastic cells with abundant cytoplasm and karyopyknosis, as well as positive IHC staining for P40 and P63. Immunostains showed that the tumour cells were strongly positive for cytokeratin (CK), HCG, Ki-67 and the master gene NLRP7 (Figure 1C), confirming the diagnosis of CC. Repeated PET-CT displayed a significant reduction in these lesions and a remarkable decrease in the standardized uptake value (SUV) (Figure 1B).
case_images: Tumor microenvironment of this patient. (A) Targeted next-generation sequencing analysis (483-gene panel) showed high tumor mutation burden (33.571 muts/MB). (B) Multiplex immunofluorescence staining results.
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case_images: Microsatellite stability status and high tumour mutation burden were identified by targeted next-generation sequencing analysis (483-gene panel, Cloudgene, China) (Supplementary Table and Figure 2A). T-cell and CD20+/ CD27+ B-cell infiltration were observed (Figure 2B). The patient received docetaxel and cisplatin (DC, both 75 mg/kg every 3 wk) chemotherapy combined with immunotherapy (tirelizumab, an anti-PD-1 antibody developed in China, 200 mg every 3 wk) and was then transferred to a community hospital for palliative care.
case_images: DNA polymorphic analysis. (A-D) Genetic profiles of 21 highly polymorphic short tandem repeats (STRs) from tumor, the patient and spouse were compared. At 7/21 valid loci (D19S433, D7S820, D8S1179, TPOX, Penta E, D12S391, FGA) examined, tumor sample was found to contained both the maternal and paternal allele, demonstrating its gestational origin. Y-axis: fluorescence intensity of the labeled product. X-axis: allelic sizes in base pairs, such that the number stands for repeat size in each short tandem repeat locus and can be highly variable among individuals.
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case_images: At 7/21 valid loci examined, the tumour sample was found to contain both the maternal and paternal alleles (nonhydatidiform triploid), demonstrating its gestational origin (Figure 3A-D).
case_images: Clinical course. The patient underwent gingival resection, relapse, and was transferred to our hospital to receive 2 cycles of DC+ICI treatment, followed by 3 cycles of FEVA chemotherapy. Pathologic images revealed the biphasic growth pattern of cytotrophoblasts (yellow triangle) and syncytiotrophoblasts (yellow arrow). Dynamic observation of lesions imaging (red arrow) and beta-HCG levels were shown below.
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case_images: Despite the dose reduction in the 3rd cycle of chemotherapy, the patient's status worsened with sepsis and multiorgan failure and ultimately succumbed to death (Figure 4).