MET exon 14 skipping mutation, amplification and overexpression in pulmonary sarcomatoid carcinoma: A multi-center study.

BACKGROUND: High frequency of MNNG HOS transforming (MET) exon 14 skipping mutation (MET exon 14Δ) has been reported in pulmonary sarcomatoid carcinomas (PSCs). However, the frequencies differ greatly. Our study aims to investigate the frequency of MET alterations and the correlations among MET exon 14Δ, amplification, and protein overexpression in a large cohort of PSCs. MET exon 14Δ, amplification, and protein overexpression were detected in 124 surgically resected PSCs by using Sanger sequencing, fluorescent in situ hybridization (FISH), and immunohistochemistry (IHC) respectively. MET exon 14Δ was identified in 9 (7.3%) of 124 cases, including 6 pleomorphic carcinomas, 2 spindle cell carcinomas and 1 carcinosarcoma. MET amplification and protein overexpression were detected in 6 PSCs (4.8%) and 25 PSCs (20.2%), respectively. MET amplification was significantly associated with overexpression (P < 0.001). However, MET exon 14Δ has no correlation with MET amplification (P = 0.370) and overexpression (P = 0.080). Multivariable analysis demonstrated that pathologic stage (hazard ratio [HR], 2.78; 95% confidence interval [CI], 1.28-6.01; P = 0.010) and MET amplification (HR, 4.71; 95% CI, 1.31-16.98; P = 0.018) were independent prognostic factors for poor median overall survival (mOS). MET alterations including MET exon 14Δ and amplification should be recommended as routine clinical testing in PSCs patients who may benefit from MET inhibitors. MET IHC appears to be an efficient screen tool for MET amplification in PSCs.

Primary esophageal mucosa-associated lymphoid tissue lymphoma: A case report and review of literature.

RATIONALE: Mucosa-associated lymphoid tissue (MALT) lymphoma is a low grade malignant B cell lymphoma which occurs mainly in the organs having mucosal layer. Though gastrointestinal tract is the most commonly involved extranodal site, primary esophageal MALT lymphoma is very rare with less than 20 cases reported in literature. PATIENT CONCERNS: A 75-year-old man was referred to our hospital for evaluation of dysphagia. Endoscopy revealed a submucosal tumor located in the middle and lower third of esophagus. CT chest and endoscopic ultrasound revealed a 15.5 × 5.9 × 4.0 cm well circumscribed submucosa esophageal tumor. Test for serum antibody against H. pylori was negative. Due to the large tumor size, patient underwent surgical resection. Histological examination showed a submucosal tumor consisting of multiple nodules of varying sizes with intact covering squamous epithelium. The nodules were mainly composed of diffusely and monoclonal proliferating centrocyte-like or monocyte-like cells. Follicular colonizations were observed without lymphoepithelial lesions. The tumor cells were diffusely positive for CD20, PAX-5, Bcl-2 and follicular dendritic cells were positive for CD21, CD23. Monoclonal gene rearrangement was positive for immunoglobulin heavy chain gene, Kappa light chain gene and Lambda light chain gene. DIAGNOSES: Based on these findings, final diagnosis of esophageal MALT lymphoma was made. OUTCOMES: At 8 month follow up, no recurrence or metastases was detected. LESSONS: Esophageal MALT lymphoma is a rare disease with definitive diagnosis possible only after histopathological examination. It carries good prognosis due to low malignant potential.