Objective:To investigate clinicopathologic characteristics and molecular genetic profiles of embryonal rhabdomyosarcoma (ERMS) of the middle ear.Methods:A total of 11 cases of primary middle ear ERMS diagnosed and treated at the Fudan University Affiliated Eye and ENT Hospital between January 2016 and June 2024 were collected. Their clinicopathologic features, immunophenotypes, and molecular genetic alterations were analyzed. Relevant literature was reviewed.Results:There were 8 male and 3 female children. The mean age was 6 years, median age, 6 (5, 7) years, with a range of 1 to 11 years. Clinical manifestations included otorrhea, ear pain, ear fullness, tinnitus, and hearing loss, with some patients also presenting with facial paralysis, hoarseness, and choking on drinking. Otoscopic examination revealed granulomatous neoplasms in the external auditory canal. Imaging studies showed irregular soft-tissue masses in the middle ear region, accompanied by bony destruction and invasion of adjacent structures. Histologically, 10 of the tumors were composed of primitive small round cells, stellate cells, and short spindle-shaped cells, with an alternating loose and dense distribution pattern, and varying degrees of rhabdomyoblastic differentiation in some areas. One tumor exhibited the classic botryoid subtype morphology. Immunohistochemistry supported the diagnosis of rhabdomyosarcoma, and the Ki-67 proliferation index ranged from 40% to 80%. Next-generation sequencing (DNA-seq) was performed on 9 cases, revealing copy number variations of chromosome 7 in 4 cases, PDE4DIP mutations in 5 cases, and C19orf69::TPM3 gene fusions in 6 cases. HPV PCR testing showed HPV11 positivity in 2 cases. All 11 patients underwent surgical treatment, with 4 patients receiving adjuvant chemoradiotherapy. Follow-up until February 2025 revealed 8 deaths, among which 4 cases harbored both C19orf69::TPM3 fusions and PDE4DIP mutations and one had C19orf69::TPM3 fusions alone.Conclusions:ERMS of the middle ear is a rare type of malignant tumor with a relatively poor prognosis. Our study indicates that the concurrence of PDE4DIP mutation and C19orf69::TPM3 gene fusion may indicate poor prognosis in middle ear EMRS, providing a potential target for subsequent individualized treatment.

Objective:To investigate the expression of keratin 1 (KRT1) and sialyl-Tn antigen (sTn) in cervical squamous cell carcinoma and its possible mechanism.Methods:Six cervical squamous cell carcinoma specimens were collected at the First Affiliated Hospital of Soochow University, Suzhou, China from 2022 to 2023. Spatial transcriptomics analysis was performed on the paraffin sections of 6 patients to analyze the transcriptomes of invasive squamous cell carcinoma and adjacent normal cervical squamous epithelium. The differential gene KRT1 was selected. Kaplan-Meier survival analysis was used to examine the prognostic value of KRT1 in cervical squamous cell carcinoma patients using the TCGA database. The possible downstream molecule sTn was identified according to literature research. Immunohistochemistry was carried out to investigate the expression of KRT1 and sTn proteins in the primary tumor and metastases of cervical squamous cell carcinoma (40 cases with pelvic lymph node metastasis and 30 cases without). Spearman correlation analysis was conducted to analyze the correlation of their expression.Results:The spatial transcriptomic results of the 6 specimens indicated that the level of KRT1 mRNA significantly decreased in cervical squamous cell carcinoma (compared with that in adjacent normal cervical squamous epithelium), while Kaplan-Meier survival analysis revealed that cervical squamous cell carcinoma patients with low KRT1 mRNA levels (versus high) had a worse prognosis. Immunohistochemistry proved that KRT1 expression was significantly lower in cervical squamous cell carcinoma than in adjacent normal squamous epithelium ( P<0.05), but sTn showed the opposite change (increased in carcinoma, P<0.05). The expression changes of KRT1 and sTn were inversely correlated ( r=-0.217, P<0.05). In addition, the expression levels of KRT1 and sTn in lymph node metastases were not significantly different from those in primary tumors. Conclusions:The decreased expression of KRT1 in primary cervical squamous cell carcinoma and lymph node metastasis may promote tumor cell proliferation and inhibit apoptosis by upregulating sTn, contributing to the poor prognosis of advanced cervical squamous cell carcinoma.

Objective:To investigate the clinicopathological features, immunophenotype and molecule characteristics of EWSR1::CREM fusion malignant epithelioid neoplasm in soft tissue.Methods:The clinical and pathological data of 2 cases of EWSR1::CREM fusion malignant epithelioid neoplasm in soft tissue diagnosed at the Department of Pathology, Beijing Jishuitan Hospital, Beijing, China from May 2023 to May 2024 were analyzed. Immunohistochemical study, fluorescence in situ hybridization (FISH) and next generation sequencing (NGS) were performed. Relevant literature was reviewed.Results:There were one male and one female patients, aged 35 and 29 years, respectively. The tumors developed in the somatic soft tissue, including calf and chest wall, and were 6.0 and 6.2 cm in size, respectively. The imaging studies suggested space-occupying lesions in muscle tissue. Case 1 did not involve the bone, while Case 2 showed fracture of the 8th rib. Microscopically, a fibrous pseudocapsule surrounded by lymphocytes and plasma cells was identified. The tumors were composed of small to medium-sized round and short spindle-shaped cells, showing nodular or sheet-like pattern. The tumor cells showed round nuclear outline, coarse chromatin with prominent nucleoli. Immunohistochemically, tumor cells showed diffuse positivity of ALK (D5F3), MUM1 and Syn, focal or patchy positivity of CKpan, EMA, S-100, NSE, WT-1 and SMA, and a high Ki-67 index (20%-30%). FISH demonstrated break-apart signals of EWSR1 gene in the 2 cases. NGS revealed EWSR1::CREM gene fusion. Case 2 showed an ATRX gene mutation. The two patients were free of recurrence or metastasis at the 10-month and 1-month follow-up, respectively.Conclusions:EWSR1::CREM fusion malignant epithelioid neoplasm is rare and lacks distinctive morphological and immunohistochemical features. FISH and NGS can help make a definitive diagnosis.

Colorectal cancer (CRC) is one of the most malignant tumors with high morbidity and mortality worldwide. Early diagnosis and accurate pathological evaluation are of great significance for improving patient prognosis. Endoscopic resection is the main treatment for early CRC. Pathological parameters-such as margin status, lymphatic vascular invasion (LVI), tumor grade, depth of submucosal invasion and tumor budding are the key to determine whether curative resection is achieved. At present, the measurement method of submucosal invasion depth of pT1 CRC is controversial. Submucosal invasion depth measurement adopts different measurement methods for pedunculated and sessile lesions, mainly including measurement from the surface of the lesion or the lower edge of the mucosal muscle layer. Especially for sessile lesions, due to different observers different understandings of the position of the mucosal muscle layer that can be identified or evaluated in the guidelines, observers may apply different criteria to evaluate the integrity of the mucosal muscle layer. In recent years, more and more evidence has shown that the association between the depth of submucosal invasion and the risk of lymph node metastasis may be overestimated, while other pathological parameters (such as LVI, high-grade tumor budding, and poorly differentiated components) have equal or more important significance in prognostic stratification. Therefore, the current measurement of the depth of submucosal invasion of pT1 CRC and its prognostic value are facing challenges, which deserve our attention and further exploration.

Pediatric tumors differ significantly from adult cancers, possessing unique developmental origins, histological features, and molecular genetic changes. With the rapid advancement of multi-omics technologies, such as genomics, transcriptomics, proteomics, and epigenetic analyses, the molecular characteristics of pediatric tumors have been extensively revealed, providing new possibilities for precision medicine. Concurrently, the integration of artificial intelligence and digital pathology has effectively enhanced diagnostic accuracy, presenting a broad scope for future development. While this progress positively impacts the pathological diagnosis of pediatric tumors, it also presents challenges related to data complexity, technology integration, and the promotion of clinical applications. This article aims to discuss the influence of molecular and artificial intelligence, as well as multimodal integrated pathological models on diagnosis and prognostic prediction of pediatric tumor, with the goal of fostering further exploration and in-depth research.

In the past decade, breast pathology in China has made significant progress in diagnostic standards, technological applications, scientific research, and discipline development. The histopathological diagnostic system has been continuously refined, with the implementation of relevant guidelines and expert consensus enhancing standardization and reproducibility of diagnostic results. Immunohistochemistry and molecular testing technologies have become increasingly sophisticated, with emerging biomarkers such as low HER2 expression and PIK3CA mutations gradually integrated into clinical decision-making, promoting the advancement of precision therapy. The application of digital pathology and image-assisted analysis has steadily expanded, providing new tools to improve diagnostic efficiency and consistency. The national breast pathology group has actively advanced the development of tiered diagnostic systems, workforce training, and public education, effectively strengthening diagnostic capabilities at the grassroots level. Looking ahead, the integration of multidimensional data, optimization of auxiliary diagnostic systems, and interdisciplinary collaboration are expected to drive the continued development of breast pathology in China.

Objective:To investigate the clinicopathological and molecular characteristics of neurocutaneous melanosis in children caused by NRAS gene variants.Methods:Three cases of neurocutaneous melanosis from Children's Hospital of Fudan University (case 1 and case 2) and Shanghai Children′s Hospital, School of Medicine Shanghai Jiaotong University (case 3) from July 2022 to February 2023 were collected. The clinical, histopathological, immunohistochemical and genetic results of three patients were retrospectively analyzed. The literatures were reviewed.Results:The patients were all female, aged 5, 4 and 3 years, respectively. The patients presented with severe headache with other symptoms of increased intracranial pressure. Physical examination showed multiple congenital melanocytic nevi throughout the body. Imaging examination showed intracranial masses, which were located in the right cerebellum, pineal gland and left temporal lobe, respectively. The maximum diameters were 39.1 mm, 72.8 mm and 52.2 mm, respectively. Histologically, the tumor showed diffuse sheets of round or oval-shaped cells arranged in nests, with marked nuclear atypia, eosinophilic cytoplasm, dark nuclei, and prominent nucleoli. Giant tumor cells were seen and mitotic figures were easily observed. There were hemorrhage and necrosis. Pigment granules were found in the cytoplasm and stroma in case 1 and case 2. Immunohistochemically, the tumor cells showed diffuse and strong staining of SOX10, S-100, HMB45 and Melan A, but did not express GFAP and CKpan. The Ki-67 proliferation index ranged from 30% to 80%. Genetic testing showed that case 1 and case 2 had NRAS Q61K matation, and case 3 had NRAS Q61R mutation. Case 1 and case 3 underwent complete resection of the tumor combined with chemotherapy. Case 2 was diagnosed by biopsy and underwent resection after chemotherapy and radiotherapy. All patients were followed up for 18, 21 and 25 months, respectively. All patients died due to complications such as increased intracranial pressure and hydrocephalus.Conclusions:Neurocutaneous melanosis is a congenital neurocutaneous syndrome caused by abnormal development of embryonic neuroectodermal melanoblasts. Most cases are associated with somatic mutations of NRAS gene. Clinicians should pay attention to the skin manifestations and neuroimaging examination in patients with unexplained intracranial hypertension or epilepsy. The diagnosis of neurocutaneous melanosis depends on histopathology and genetic testing.

Objective:To explore the consistency of claudin 18.2 immunohistochemistry (IHC) using 4 different clone antibodies in gastric adenocarcinoma.Methods:A total of 226 gastric adenocarcinomas diagnosed and treated at the Drum Tower Hospital Affiliated to Nanjing University Medical College between January 2022 to March 2023 were included in this study. The cohort consisted of 165 males and 61 females, with a mean age of (61.3±12.1) years. Tumor tissues from radical resection specimens were collected for tissue microarrays. IHC detection of claudin 18.2 was performed using the EnVision method, utilizing 4 clones of antibody: OTIR157B5, 43-14A, EPR19202 and D313D22. The results were interpreted based on both the intensity of staining on tumor cell membranes and the percentage of positive tumor cells relative to the total tumor cells.Results:The positive cutoff value was set as moderately to strongly linear membrane staining in ≥75% of all viable invasive tumor cells, and clone OTIR157B5 demonstrated the highest positive expression rate at 52.2% (118/226). Additionally, the clones OTIR157B5, 43-14A, and EPR19202 were consistently and strongly positive, with all agreement rates of Cohen κ exceeding 0.8. In gastric adenocarcinoma and its three Lauren subtypes, OTIR157B5 exhibited clear membranous localization.Conclusions:Clone OTIR157B5 of claudin 18.2 antibody shows the highest rate of moderately to strongly linear membrane-positive staining, accounting for ≥75% of all viable invasive tumor cells, and clones 43-14A and EPR19202 show strong consistency and high sensitivity.

Objective:To investigate the clinicopathological characteristics of type 2 autoimmune pancreatitis (AIP) and to explore its relationship with inflammatory bowel disease (IBD).Methods:AIP cases confirmed by pathology in the First Affiliated Hospital of Zhejiang University School of Medicine from 2009 to 2024 were collected. According to the International Consensus Diagnostic Criteria (ICDC) for AIP, 11 patients were identified as histological level 1 (definite) or level 2 (probable) type 2 AIP. Their clinical manifestations, laboratory test results, imaging features, and histopathological characteristics were analyzed, and a follow-up was conducted. Meanwhile, 130 patients with type 1 AIP diagnosed in our hospital during the same period were selected as control group.Results:Among 141 AIP patients, 11 cases (7.8%, 11/141) were diagnosed with type 2 AIP, including 7 cases of histologically level 1 and 4 cases of level 2. There were 10 male patients and 1 female patient, with a median age of 37(31,46) years (range: 25-47 years). Three patients were complicated with ulcerative colitis (UC). Compared with type 1 AIP patients, type 2 AIP patients were younger, often presented with acute pancreatitis or abdominal pain as the initial symptom, and had a close association with IBD ( P<0.05). Laboratory tests showed that only 1 patient had slightly elevated serum IgG4, while the other 10 patients had normal serum IgG4 levels. Serum CA19-9 was elevated in 8 patients, and the percentage of peripheral blood neutrophils was increased in 9 patients. Imaging findings revealed diffuse pancreatic enlargement in 8 patients and localized enlargement in 3 patients (2 cases in the pancreatic head and 1 case in the pancreatic body-tail). Magnetic resonance cholangiopancreatography (MRCP) showed main pancreatic duct stenosis in 5 cases (5/7). Histopathological features included 7 cases of level 1 type 2 AIP that showed neutrophilic infiltration in the pancreatic duct epithelium and massive neutrophilic infiltration between the acini. Immunohistochemistry showed that only 1 case had <5 IgG4-positive plasma cells per high-power field (HPF), while the other 10 cases were negative. All 11 patients with type 2 AIP received steroid therapy, and no recurrence was observed during the follow-up period of 5 to 174 months. Conclusions:Type 2 AIP has unique clinicopathological characteristics. It is more commonly found in young patients and often presents with manifestations similar to acute pancreatitis. Histologically, neutrophilic infiltration in the ductal epithelium is the common feature. Type 2 AIP is closely associated with IBD, especially UC.

Objective:To investigate the clinicopathological characteristics and genetic alterations of undifferentiated embryonal sarcoma of the liver (UESL).Methods:Three cases of UESL diagnosed in the Department of Pathology, the Third Affiliated Hospital of Sun Yat-sen University from 2020 to 2023 were retrospectively collected. The clinical, histomorphological, immunohistochemical, and genetic profiles were reviewed and analyzed.Results:The cohort comprised of three patients, including one male and two females, aged 7, 9, and 15 years, respectively. Tumor locations were in the right lobe of the liver in two cases, and in both the right and left lobes in one case. One case exhibited tumor rupture with hemorrhage. Gross examination revealed solid tumors in gray-red fleshy appearance, with areas of hemorrhage and necrosis. Microscopically, the tumor was composed of irregularly shaped spindle and polygonal cells arranged in bundles or sheets with varying density, scattered within a myxoid matrix containing giant tumor cells and eosinophilic globules. The tumor cells were positive for Vimentin, CD56, CD68, and bcl-2, with a Ki-67 index of 30%-80%. INI1 expression was retained, while p53 exhibited a mutant pattern. CKpan, CK7, CK19, EMA, HepPar-1, Arginase-1, AFP, CD34, S-100, Myogenin, and MyoD1 were negative. All three cases harbored TP53 missense mutations. Case 1 also showed MDM2 copy number amplification (class Ⅰ mutation), and case 2 exhibited a frameshift mutation in exon 10 of TSC2 (class Ⅱ mutation). Additionally, several class Ⅲ mutations were identified in all three cases. Germline testing for tumor-related genetic variants in case 2 revealed a missense mutation in exon 12 of DICER1, an in-frame insertion mutation in exon 8 of MSH2, and a missense mutation in exon 30 of TSC2.Conclusion:UESL is a rare malignant mesenchymal tumor of the liver, predominantly affecting children, with distinctive clinicopathological features and genetic alterations. TP53 mutations may play a key role in the pathogenesis of this tumor.