Mucin phenotype and genetic alterations in non-V600E BRAF-mutated colorectal cancer.

Colorectal cancer (CRC) is a heterogeneous disease that develops through stepwise accumulation of genetic alterations and progresses via several distinct pathways. However, the tumorigenesis of CRCs with BRAF non-V600E mutations remains unclear. Here, we aimed to elucidate the tumorigenesis of CRCs with BRAF non-V600E mutations, focusing on differences in mucin phenotype and genetic alterations between CRCs with non-V600E and V600E mutations. We investigated 201 patients with CRC and performed panel testing of 415 genes to identify BRAF mutations. Patients were classified into five mucin phenotypes - large-intestinal, small-intestinal, gastric, mixed, and unclassified - using immunohistochemistry for CD10, MUC2, MUC5AC, and MUC6. BRAF mutations were identified in 24 of 201 patients' samples, of which 13 (6.5%) had a V600E mutation (V600E-mutant) and 11 (5.5%) had non-V600E mutations (non-V600E-mutant). MUC5AC expression was significantly associated with V600E mutations (P = 0.040), while CD10 expression was significantly associated with non-V600E mutations (P = 0.010). The small-intestinal mucin phenotype was significantly associated with non-V600E mutations (P = 0.031), while the mixed mucin phenotype was significantly associated with V600E mutations (P = 0.027). Regarding genetic alterations, focusing on the WNT signaling pathway, APC mutation was significantly associated with non-V600E mutations (P < 0.001), while RNF43 mutation was significantly associated with V600E mutations (P = 0.020). Considering the differences in mucin phenotype and genetic alterations, different modes of tumorigenesis are assumed for CRC with BRAF V600E mutation and non-V600E mutations. These findings are important in understanding the biology and treatment strategies for BRAF-mutant CRC.

An adenocarcinoma in an inverted Meckel's diverticulum with intussusception.

BACKGROUND: Adenocarcinoma in an inverted Meckel's diverticulum with intussusception has not been reported to date. We discuss the clinical issues concerning this rare condition and review the relevant literature. CASE PRESENTATION: A 71-year-old Japanese female was referred to our hospital for further investigation of severe anemia. Computed tomography revealed a tumorous lesion in the terminal ileum. Capsule endoscopy did not provide detailed images. Exploratory laparoscopy revealed intussusception in the terminal ileum. An intraluminal tumor 70 cm proximal to the ileocecal valve was observed to be the lead point. Partial resection including the tumor was performed. Macroscopically, a polypoid tumor at the tip of an inverted diverticulum-like structure was observed. The tumor was histologically composed of adenocarcinoma accompanied by gastric and pyloric gland metaplasia in the background mucosa, which was confirmed by immunohistochemical staining. Based on these characteristics, this tumor is considered to have developed from the ectopic gastric mucosa in a Meckel's diverticulum. CONCLUSIONS: When we encounter patients with unfamiliar lesions in the small bowel, we need to differentiate Meckel's diverticulum related disease. Meckel's diverticulum can invert into the lumen of the small bowel and cause an intussusception, and has potential of malignant transformation.

[Paraneoplastic anti-gamma aminobutyric acid (GABA)B receptor antibody limbic encephalitis associated with small cell lung cancer presenting as new-onset status epilepticus: a case report].

An 84-year-old man was admitted to our hospital with new-onset refractory status epilepticus of unclear etiology. On the third day, diffusion-weighted brain MRI demonstrated lesions in the right medial temporal and parietal lobes. As a CSF sample showed pleocytosis, paraneoplastic limbic encephalitis (PLE) associated with small cell lung cancer (SCLC) was suspected. The patient was also positive for anti-gamma aminobutyric acid (GABA)B receptor antibody in the CSF, which has recently been reported in elderly patients with SCLC-related PLE. Methylprednisolone pulse therapy ameliorated the symptoms. It is noteworthy that immune therapy often improves the symptoms of PLE with anti-GABAB receptor antibody, even though radical therapy for the lung cancer may be difficult.