Purpose: Claudin 18.2 (CLDN18.2) has emerged as a promising therapeutic target for CLDN18.2-expressing gastric cancer (GC). We sought to examine the heterogeneity of CLDN18.2 expression between primary GC (PGC) and metastatic GC (MGC) using various scoring methods. Materials and Methods: We retrospectively analyzed data from 102 patients with pathologically confirmed paired primary and metastatic gastric or gastroesophageal junction adenocarcinomas. CLDN18.2 expression was evaluated through immunohistochemistry on formalin-fixed paraffin-embedded tissue samples. We assessed CLDN18.2 positivity using multiple scoring approaches, including the immunoreactivity score, H-score, and the percentage of tumor cells showing moderate-to-strong staining intensity. We analyzed the concordance rates between PGC and MGC and the association of CLDN18.2 positivity with clinicopathological features. Results: CLDN18.2 positivity varied from 25% to 65% depending on the scoring method, with PGC consistently showing higher expression levels than MGC. Intratumoral heterogeneity was noted in 25.5% of PGCs and 19.6% of MGCs. Intertumoral heterogeneity, manifesting as discordance in CLDN18.2 positivity between PGC and MGC, was observed in about 20% of cases, with moderate agreement across scoring methods (κ=0.47 to 0.60).In PGC, higher CLDN18.2 positivity correlated with synchronous metastasis, presence of peritoneal metastasis, poorly differentiated grade, and biopsy specimens. In MGC, positivity was associated with synchronous metastasis, presence of peritoneal metastasis, and metastatic peritoneal tissues. Conclusions CLDN18.2 expression demonstrates significant heterogeneity between PGC and MGC, with a 20% discordance rate. Comprehensive tissue sampling and reassessment of CLDN18.2 status are crucial, especially before initiating CLDN18.2-targeted therapies.

Purpose: Claudin 18.2 (CLDN18.2) has emerged as a promising therapeutic target for CLDN18.2-expressing gastric cancer (GC). We sought to examine the heterogeneity of CLDN18.2 expression between primary GC (PGC) and metastatic GC (MGC) using various scoring methods. Materials and Methods: We retrospectively analyzed data from 102 patients with pathologically confirmed paired primary and metastatic gastric or gastroesophageal junction adenocarcinomas. CLDN18.2 expression was evaluated through immunohistochemistry on formalin-fixed paraffin-embedded tissue samples. We assessed CLDN18.2 positivity using multiple scoring approaches, including the immunoreactivity score, H-score, and the percentage of tumor cells showing moderate-to-strong staining intensity. We analyzed the concordance rates between PGC and MGC and the association of CLDN18.2 positivity with clinicopathological features. Results: CLDN18.2 positivity varied from 25% to 65% depending on the scoring method, with PGC consistently showing higher expression levels than MGC. Intratumoral heterogeneity was noted in 25.5% of PGCs and 19.6% of MGCs. Intertumoral heterogeneity, manifesting as discordance in CLDN18.2 positivity between PGC and MGC, was observed in about 20% of cases, with moderate agreement across scoring methods (κ=0.47 to 0.60).In PGC, higher CLDN18.2 positivity correlated with synchronous metastasis, presence of peritoneal metastasis, poorly differentiated grade, and biopsy specimens. In MGC, positivity was associated with synchronous metastasis, presence of peritoneal metastasis, and metastatic peritoneal tissues. Conclusions CLDN18.2 expression demonstrates significant heterogeneity between PGC and MGC, with a 20% discordance rate. Comprehensive tissue sampling and reassessment of CLDN18.2 status are crucial, especially before initiating CLDN18.2-targeted therapies.

Purpose: Claudin 18.2 (CLDN18.2) has emerged as a promising therapeutic target for CLDN18.2-expressing gastric cancer (GC). We sought to examine the heterogeneity of CLDN18.2 expression between primary GC (PGC) and metastatic GC (MGC) using various scoring methods. Materials and Methods: We retrospectively analyzed data from 102 patients with pathologically confirmed paired primary and metastatic gastric or gastroesophageal junction adenocarcinomas. CLDN18.2 expression was evaluated through immunohistochemistry on formalin-fixed paraffin-embedded tissue samples. We assessed CLDN18.2 positivity using multiple scoring approaches, including the immunoreactivity score, H-score, and the percentage of tumor cells showing moderate-to-strong staining intensity. We analyzed the concordance rates between PGC and MGC and the association of CLDN18.2 positivity with clinicopathological features. Results: CLDN18.2 positivity varied from 25% to 65% depending on the scoring method, with PGC consistently showing higher expression levels than MGC. Intratumoral heterogeneity was noted in 25.5% of PGCs and 19.6% of MGCs. Intertumoral heterogeneity, manifesting as discordance in CLDN18.2 positivity between PGC and MGC, was observed in about 20% of cases, with moderate agreement across scoring methods (κ=0.47 to 0.60).In PGC, higher CLDN18.2 positivity correlated with synchronous metastasis, presence of peritoneal metastasis, poorly differentiated grade, and biopsy specimens. In MGC, positivity was associated with synchronous metastasis, presence of peritoneal metastasis, and metastatic peritoneal tissues. Conclusions CLDN18.2 expression demonstrates significant heterogeneity between PGC and MGC, with a 20% discordance rate. Comprehensive tissue sampling and reassessment of CLDN18.2 status are crucial, especially before initiating CLDN18.2-targeted therapies.

Progressive multifocal leukoencephalopathy (PML) is a demyelinating disease by John Cunningham virus (JC virus) infection in oligodendrocytes. The radiographic and clinical features,along with the identification JC in cerebrospinal fluid polymerase chain reaction, are sufficient for the diagnosis of PML in immunodeficiency. However, it is difficult to suspect PML without the patient history of immunodeficiency. A 32-year-old man presented with headache for a month without any medical history. Based on clinical and image features, the differential di-agnoses included demyelinating lesion and neoplasms. Microscopically, biopsy specimen showed multifocal demyelinating and degenerative white matter, consistent with PML. Oligodendrocytes cells with increased nuclei and plum-colored inclusions were admixed withperivascular lymphocytic and histiocytic infiltration, and loss of myelin. Atypical astrocytes had large or multiple nuclei. After brain biopsy, human immunodeficiency virus infection was confirmed by serum chemiluminescent immunoassay. It is unlikely that PML would be con-sidered without the information of immunosuppression. Therefore, it is very important to be aware of the histological features of PML.

Background: Research regarding cervical metastasis from an unknown primary tumor (CUP) according to human papillomavirus (HPV) and Epstein-Barr virus (EBV) status in Korea has been sporadic and small-scale. This study aims to analyze and understand the characteristics of CUP in Korea according to viral and p16 and p53 status through a multicenter study. Methods: Ninety-five cases of CUP retrieved from six hospitals in Korea between January 2006 and December 2016 were subjected to high-risk HPV detection (DNA in situ hybridization [ISH] or real-time polymerase chain reaction), EBV detection (ISH), and immunohistochemistry for p16 and p53. Results: CUP was HPV-related in 37 cases (38.9%), EBV-related in five cases (5.3%), and unrelated to HPV or EBV in 46 cases (48.4%). HPV-related CUP cases had the best overall survival (OS) (p = .004). According to the multivariate analysis, virus-unrelated disease (p = .023) and longer smoking duration (p < .005) were prognostic factors for poor OS. Cystic change (p = .016) and basaloid pattern (p < .001) were more frequent in HPV-related cases, and lymphoepithelial lesion was frequent in EBV-related cases (p = .010). There was no significant association between viral status and p53 positivity (p = .341), smoking status (p = .728), or smoking duration (p = .187). Korean data differ from Western data in the absence of an association among HPV, p53 positivity, and smoking history. Conclusions Virus-unrelated CUP in Korea had the highest frequency among all CUP cases. HPV-related CUP is similar to HPV-mediated oropharyngeal cancer and EBVrelated CUP is similar to nasopharyngeal cancer in terms of characteristics, respectively.

Biliary hamartomas are tumor-like malformations of the liver. Biliary hamartomas are a type of fibrocystic disorder originating from ductal plate malformation and are typically considered benign, but with the risk of malignant transformation. In this case report, we present a rare occurrence of intrahepatic cholangiocarcinoma (ICC) that developed from biliary hamartomas, along with a literature review. A 76-year-old man with a diagnosis of biliary hamartomas had a history of recurrent cholangitis for 12 years, necessitating cholecystectomy, ERCP, and repeated antibiotic treatments. During his last episode, imaging studies revealed a hypervascular infiltrative mass in the right posterior liver segment. A liver biopsy confirmed adenocarcinoma and subsequent surgical pathology revealed ICC originating from biliary hamartomas. Chronic inflammation in the bile duct associated with biliary hamartomas may serve as a potential trigger for malignant transformation, as observed in this case. Therefore, close surveillance is essential for patients with biliary hamartomas presenting with infectious complications.

As more individuals were coronavirus disease 2019 (COVID-19) vaccinated, unexpected side effects appeared. Herein, we present the case of a 30-year-old male patient with myopathy in both extremities after the second dose of the Pfizer-BioNTech (BNT162b2) COVID-19 vaccine. Symptoms, swelling and pain, started from the proximal upper and lower extremities and extended to the distal parts. Although he underwent massive hydration, the muscle enzyme level continuously increased. He complained of dysphagia and dysarthria.Microscopically, muscle biopsy showed multifocal or scattered macrophage infiltration and degenerated myofibers. In contrast to general myopathy including inflammatory myositis and rhabdomyolysis, vaccine-induced inflammatory myositis shows a prolonged increase in muscle enzyme levels and multifocal macrophage infiltration with necrosis of the muscle fibers. Symptoms improved with glucocorticoid and immunosuppressive treatment. If vaccinated individuals experience severe and continuous muscle pain and swelling, clinicians should consider vaccine-induced inflammatory myositis, measure the muscle enzyme levels, and perform muscle biopsy for a definite diagnosis.

Purpose: To determine the multidetector CT (MDCT) findings that differentiate adenomyoma of the ampulla of Vater (AOV) from localized adenocarcinoma of the AOV. Materials and Methods: Sixteen and 30 patients with adenomyoma and localized adenocarcinoma of the AOV, respectively, were evaluated using MDCT. We analyzed the size and attenuation value and presence of uniform enhancement of the lesions, diameters of the extrahepatic bile duct (EHD) and main pancreatic duct, presence of regional lymph node enlargement, and laboratory findings. We determined the independent findings for differentiating adenomyoma from localized adenocarcinoma of the AOV using multivariate analysis. Results: The size of the lesion and diameter of the EHD were significantly smaller for adenomyoma than those for localized adenocarcinoma of the AOV (all p < 0.001). In multivariate analyses, a lesion size of ≤ 1.3 cm, an EHD diameter of ≤ 1.3 cm, and an alanine transaminase level of ≤ 31 IU/L significantly differentiated adenomyoma from localized adenocarcinoma of the AOV. When all of these three findings were met, the specificity for adenomyoma of the AOV was 93.3%. Conclusion MDCT imaging may facilitate the differential diagnosis of adenomyoma and localized adenocarcinoma of the AOV based on the size of the lesion and diameter of the EHD.

Purpose: To determine the multidetector CT (MDCT) findings that differentiate adenomyoma of the ampulla of Vater (AOV) from localized adenocarcinoma of the AOV. Materials and Methods: Sixteen and 30 patients with adenomyoma and localized adenocarcinoma of the AOV, respectively, were evaluated using MDCT. We analyzed the size and attenuation value and presence of uniform enhancement of the lesions, diameters of the extrahepatic bile duct (EHD) and main pancreatic duct, presence of regional lymph node enlargement, and laboratory findings. We determined the independent findings for differentiating adenomyoma from localized adenocarcinoma of the AOV using multivariate analysis. Results: The size of the lesion and diameter of the EHD were significantly smaller for adenomyoma than those for localized adenocarcinoma of the AOV (all p < 0.001). In multivariate analyses, a lesion size of ≤ 1.3 cm, an EHD diameter of ≤ 1.3 cm, and an alanine transaminase level of ≤ 31 IU/L significantly differentiated adenomyoma from localized adenocarcinoma of the AOV. When all of these three findings were met, the specificity for adenomyoma of the AOV was 93.3%. Conclusion MDCT imaging may facilitate the differential diagnosis of adenomyoma and localized adenocarcinoma of the AOV based on the size of the lesion and diameter of the EHD.

Pancreatic candidiasis can develop in patients with acute pancreatitis, compromised immune responses, or iatrogenic intervention. This paper reports a case of pancreatic candidiasis presenting as a solid pancreatic mass in a patient without the risk factors. A previously healthy 37-year-old man visited the emergency department with left flank pain. Abdominal CT revealed a 5 cm, irregular heterogeneous enhancing mass accompanied by a left adrenal mass. Positron emission tomography-computed tomography and endoscopic ultrasound-guided fine-needle aspiration (EUS-FNA) could not discriminate pancreatic cancer from infectious disease. A laparoscopic exploration was performed for an accurate diagnosis. After distal pancreatectomy with splenectomy and left adrenalectomy, pancreatic candidiasis and adrenal cortical adenoma were diagnosed based on the pathology findings. His condition improved after the treatment with fluconazole. This paper reports a case of primary pancreatic candidiasis mimicking pancreatic cancer in an immunocompetent patient with a review of the relevant literature.