Genetic analysis on formalin‐fixed paraffin‐embedded (FFPE) tissue specimens has become a mainstream method, from conventional direct sequencing to comprehensive analysis using next‐generation sequencing (NGS). In this study, we evaluated the quality of DNA and RNA extracted from FFPE sections, derived from surgical specimens of different tumor types. Electrophoresis was performed using a 4200 TapeStation to evaluate DNA and RNA fragmentation. DNA Ct values were higher and significantly increased over a period of 4 years compared with those from cell lines or frozen tissues. The RNA integrity number equivalent (RIN) ranged from 1 to 4.1 and DV200 ranged from 7.3 to 81%. Twelve of the 108 cases were analyzed by NGS using the AmpliSeq Cancer HotSpot Panel v2 on a Miniseq system. A sufficient number of reads and coverage were obtained in all cases. Our results revealed that NGS analysis was sufficient for FFPE‐derived DNA within 4 years of preservation. Conversely, approximately 20% of the RNA derived from FFPE within 4 years from the collection could be inappropriate for gene analysis based on RIN and DV200. It was suggested that FFPE would be adequate for genetic analysis, although it is desirable to store frozen specimens for the tumor tissues to be subjected to genetic analysis.

Gastritis cystica profunda (GCP) is a lesion characterized by cystic gastric glands within the submucosa. Some studies have reported that GCP is a precancerous lesion. Here, we investigated the association between GCP and gastric cancer. Gastric cancer specimens were taken from 1432 patients undergoing surgery or endoscopic submucosal resection and were classified as GCP or non‐GCP. The clinicopathological features, immunohistochemistry and in situ hybridization expression of p53, Ki‐67, KCNE2, Epstein–Barr virus (EBV) and programmed death ligand 1 (PD‐L1) were compared between the two groups, as well as between GCPs and normal pyloric glands. One hundred and eighty patients (12.6%) had GCPs. In the GCP group, no cancerous lesions were found within the GCPs, but 13% were linked to GCPs and 60.2% were located above or near GCPs. Aberrant p53 expression, EBV‐positive cancer cells and PD‐L1 scores were significantly higher in the GCP group. The p53 score and Ki‐67 labelling index were significantly higher and the KCNE2 score was significantly lower in GCPs than in pyloric glands. Although we suggest GCP is paracancerous, GCP has high proliferation activity and gastric cancer with GCP is associated with aberrant p53 and EBV. GCP is associated with aberrant p53 expression and EBV.

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AimsPulmonary enteric adenocarcinoma (PEAC) is a rare variant of pulmonary adenocarcinoma. Due to its rarity, few pathological and molecular studies have been performed on PEAC. We herein conducted clinicopathological, immunohistochemical and molecular analyses of PEAC with a focus on its differentiation from invasive mucinous adenocarcinoma (IMA).MethodsWe examined the clinicopathological features of 16 cases of PEAC and performed a genetic analysis using next-generation sequencing (NGS). The results obtained were compared with those for IMA.ResultsThe average age of patients with PEAC (seven men and nine women) was 72.9 years. A comparison of clinical data on PEAC and IMA revealed no significant differences in age, sex or smoking history. Fifteen PEAC cases had dirty necrosis. Immunohistochemically, the positive rates for each antibody in PEAC were as follows: CK7, 88% (14/16); CK20, 81% (13/16); CDX2, 88% (14/16); p53, 69% (11/16); MUC1, 100% (16/16); MUC2, 19% (3/16); MUC5AC, 69% (11/16); MUC6, 19% (3/16). The positive rates for these antibodies in IMA were 100%, 87%, 0%, 7%, 93%, 0%, 100% and 80%, respectively.EGFRmutations, theMETexon 14 skipping mutation,BRAFmutations, theALKfusion gene andROS-1fusion gene were not detected in any cases of PEAC or IMA. Among PEAC cases, NGS identifiedKRASmutations in seven (44%, 7/16) andTP53mutations in nine (56%, 9/16). Among IMA cases, the most commonly mutated gene wasKRAS(90%).ConclusionsThe rates of dirty necrosis, immunopositivity for CDX2 andTP53mutations were significantly higher, while that ofKRASmutations was significantly lower in PEAC cases than in IMA cases.

Interdigitating dendritic cell sarcoma (IDCS) is an extremely rare neoplasm arising from dendritic cells and is mainly located in the lymph nodes. To the best of our knowledge, no treatment strategy has yet been established for IDCS, despite its aggressive clinical features. The present study presents the case of a patient with IDCS who experienced a 40-month disease-free survival time after surgery alone. The patient, a 29-year-old woman, presented with a painful right subaural swelling. Diagnostic MRI and 18 F-fludeoxyglucose positron emission tomography/computed tomography revealed a right parotid gland tumour and ipsilateral cervical lymph node. The patient underwent surgical resection, and histological examination of the resected tissue specimens confirmed IDCS diagnosis. To the best of our knowledge, this is only the fifth report of an IDCS located in the parotid gland, with the longest follow-up period among cases of IDCS reported in this region. The positive outcome of this patient suggests that surgical resection may be an effective treatment option for local IDCS. Nonetheless, further studies are required to establish a definitive diagnosis and treatment strategy for IDCS.