Carcinosarcomas are high-grade endometrial cancers which enclose mesenchymal and epithelial differentiated components. The vast majority of these cancers belong to the p53 abnormal molecular subgroup and usually come with an unfavorable prognosis. POLE mutant carcinosarcomas are a rarity and only make up about 5% of this histologic subtype. Recent literature even suggests that this number is still an overestimation and the result of misclassification of undifferentiated or dedifferentiated endometrial cancers. Here we present a case of a 56-years old patient diagnosed with carcinosarcoma of the uterus. Hysterectomy, bilateral salpingo-oophorectomy with pelvic lymph node staging was performed and complete molecular workup of the tumor revealed an abnormal p53 expression as well as a pathologic POLE mutation. NGS was performed separately on the epithelial and mesenchymal component of this high-grade cancer and both components shared two identical POLE mutations, a known pathologic mutation, and a variant of unknown significance (VUS). This finding hints to a clonal origin of both histologic components of this tumor and supports conversion theory as mechanism of carcinosarcoma emergence. The cancer was correctly staged as FIGO 2023 Stage IAmPOLEmut and according to ESGO-ESTRO-ESP guidelines adjuvant chemotherapy no longer considered and our patient entered follow-up after a detailed discussion.

Central neurocytoma (CN) is classically defined by its intraventricular location, neuronal/neurocytic differentiation, and histological resemblance to oligodendroglioma. Extraventricular neurocytoma (EVN) shares similar histological features with CN, while it distributes any site without contact with the ventricular system. CN and EVN have distinct methylation landscapes, and EVN has a signature fusion gene, FGFR1-TACC1. These characteristics distinguish between CN and EVN. A 30-year-old female underwent craniotomy and resection of a left intraventricular tumor at our institution. The histopathology demonstrated the classical findings of CN. Adjuvant irradiation with 60 Gy followed. No recurrence has been recorded for 25 years postoperatively. RNA sequencing revealed FGFR1-TACC1 fusion and methylation profile was discrepant with CN but compatible with EVN. We experienced a case of anatomically and histologically proven CN in the lateral ventricle. However, the FGFR1-TACC1 fusion gene and methylation profiling suggested the molecular diagnosis of EVN. The representative case was an \"intraventricular\" neurocytoma displaying molecular features of an \"extraventricular\" neurocytoma. Clinicopathological and molecular definitions have collided in our case and raised questions about the current definition of CN and EVN.

The metastatic spread of breast carcinoma to the stomach is a rare event and often represents a diagnostic challenge. In the present study, 23 cases of gastric metastases from breast cancer were retrospectively identified dating back until 2007. Primitive histotype, localization, gross appearance, microscopic architecture were analyzed. Cytokeratins 7 and 20, sex hormones, HER2 and Ki67 expression was evaluated. According to the results, the series was characterized by an enrichment of lobular primitive histotype (43.7%). In most cases gastric metastases were described as parietal nodules, polypoid masses or ulcerated lesions, mainly involving the antro-angular region. In a relatively high rate (10.5%) of cases, endoscopic examinations resulted negative for macroscopic lesions. More than half of the cases (52.2%) microscopically resembled primitive poorly cohesive gastric cancer. Because gross and histological findings can be deceiving, immunohistochemistry may be essential for the diagnosis of gastric metastases from breast cancer. Accordingly with the results of our analysis and literature review, an immunohistochemical panel composed of cytokeratins 7 and 20, Estrogen and Progesteron Receptors would drastically improve diagnostic accuracy. Interaction among the clinician, endoscopist and the pathologist is also essential to provide the patient the best therapeutic option.

We report a case of a 26-year-old Chinese man who had experienced three grand mal seizures in the past two months. Magnetic resonance imaging revealed a relatively well-circumscribed lesion in the left frontal lobe. A craniotomy with total excision of the tumor was performed. Histopathological investigations confirmed a grade 2 ependymoma according to the World Health Organization classification. Genetic analysis revealed a tumor harboring FAM118B fusion to YAP1, and no other genetic alterations or methylation of the O6 -methylguanine-DNA methyltransferase gene promoter were detected. This is the second case report of ependymoma with YAP1:FAM118B fusion.

BACKGROUND: The concept of precision medicine in cancer includes individual molecular studies to predict clinical outcomes. In the present N = 1 case we retrospectively have analysed lymphoma tissue by exome sequencing and global gene expression in a patient with unexpected long-term remission following relaps. The goals were to phenotype the diagnostic and relapsed lymphoma tissue and evaluate its pattern. Furthermore, to identify mutations available for targeted therapy and expression of genes to predict specific drug effects by resistance gene signatures (REGS) for R-CHOP as described at http://www.hemaclass.org. We expected that such a study could generate therapeutic information and a frame for future individual evaluation of molecular resistance detected at clinical relapse.
METHODS: The patient was diagnosed with a transformed high-grade non-Hodgkin lymphoma stage III and treated with conventional R-CHOP [rituximab (R), cyclophosphamide (C), doxorubicin (H), vincristine (O) and prednisone (P)]. Unfortunately, she suffered from severe toxicity but recovered during the following 6 months\' remission until biopsy-verified relapse. The patient refused second-line combination chemotherapy, but accepted 3 months\' palliation with R and chlorambucil. Unexpectedly, she obtained continuous complete remission and is at present >9 years after primary diagnosis. Molecular studies and data evaluation by principal component analysis, mutation screening and copy number variations of the primary and relapsed tumor, identified a pattern of branched lymphoma evolution, most likely diverging from an in situ follicular lymphoma. Accordingly, the primary diagnosed transformed lymphoma was classified as a diffuse large B cell lymphoma (DLBCL) of the GCB/centrocytic subtype by \"cell of origin BAGS\" assignment and R sensitive and C, H, O and P resistant by \"drug specific REGS\" assignment. The relapsed DLBCL was classified as NC/memory subtype and R, C, H sensitive but O and P resistant.
CONCLUSIONS: Thorough analysis of the tumor DNA and RNA documented a branched evolution of the two clinical diagnosed tFL, most likely transformed from an unknown in situ lymphoma. Classification of the malignant tissue for drug-specific resistance did not explain the unexpected long-term remission and potential cure. However, it is tempting to consider the anti-CD20 immunotherapy as the curative intervention in the two independent tumors of this case.