Utility of BRAF V600E mutation-specific immunohistochemistry in detecting BRAF V600E-mutated gastrointestinal stromal tumors.

OBJECTIVES: As patients with BRAF V600E mutation respond to BRAF inhibitors, it is important to identify these mutations to stratify patients for the appropriate therapy. In this study, we evaluated the utility of a BRAF V600E allele-specific antibody in gastrointestinal stromal tumors (GISTs). METHODS: BRAF V600E mutation-specific immunohistochemistry (negative, weak, or moderate/strong expression) and BRAF sequencing were performed on 38 consecutive GISTs diagnosed between January 2013 and April 2014. RESULTS: GISTs from a cohort of 25 men and 13 women (mean age, 61 years; range, 39-88 years) were localized to the stomach (18), small bowel (10), colon (three), rectum (two), and pelvis/omentum (five). Strong and diffuse cytoplasmic BRAF expression was noted in two (5%) of 38 cases, while eight (21%) of 38 cases showed weak staining, and 28 (74%) of 38 cases were negative. Both of the strongly positive cases arose in the stomach, occurring in a 42-year-old and a 47-year-old woman, respectively. The lesions measured 0.8 and 1 cm, showed spindle cell morphology, and had no risk of progressive disease by Miettinen criteria. Both cases showed heterozygous BRAF V600E, while no BRAF mutations were detected in cases with weak or negative BRAF expression. CONCLUSIONS: BRAF V600E mutation-specific immunohistochemistry is a highly sensitive and specific method for detecting BRAF-mutated GISTs.

Novel mutations in neuroendocrine carcinoma of the breast: possible therapeutic targets.

Primary neuroendocrine carcinoma of the breast is a rare variant, accounting for only 2% to 5% of diagnosed breast cancers, and may have relatively aggressive behavior. Mutational profiling of invasive ductal breast cancers has yielded potential targets for directed cancer therapy, yet most studies have not included neuroendocrine carcinomas. In a tissue microarray screen, we found a 2.4% prevalence (9/372) of neuroendocrine breast carcinoma, including several with lobular morphology. We then screened primary or metastatic neuroendocrine breast carcinomas (excluding papillary and mucinous) for mutations in common cancer genes using polymerase chain reaction-mass spectroscopy (643 hotspot mutations across 53 genes), or semiconductor-based next-generation sequencing analysis (37 genes). Mutations were identified in 5 of 15 tumors, including 3 with PIK3CA exon 9 E542K mutations, 2 of which also harbored point mutations in FGFR family members (FGFR1 P126S, FGFR4 V550M). Single mutations were found in each of KDR (A1065T) and HRAS (G12A). PIK3CA mutations are common in other types of breast carcinoma. However, FGFR and RAS family mutations are exceedingly rare in the breast cancer literature. Likewise, activating mutations in the receptor tyrosine kinase KDR (VEGFR2) have been reported in angiosarcomas and non-small cell lung cancers; the KDR A1065T mutation is reported to be sensitive to VEGFR kinase inhibitors, and fibroblast growth factor receptor inhibitors are in trials. Our findings demonstrate the utility of broad-based genotyping in the study of rare tumors such as neuroendocrine breast cancer.

Oncogenic mutations in melanomas and benign melanocytic nevi of the female genital tract.

BACKGROUND: The genetic heterogeneity of melanomas and melanocytic nevi of the female genital tract is poorly understood. OBJECTIVE: We aim to characterize the frequency of mutations of the following genes: BRAF, NRAS, KIT, GNA11, and GNAQ in female genital tract melanomas. We also characterize the frequency of BRAF mutations in female genital tract melanomas compared with melanocytic nevi. METHODS: Mutational screening was performed on the following female genital tract melanocytic neoplasms: 25 melanomas, 7 benign melanocytic nevi, and 4 atypical melanocytic nevi. RESULTS: Of the 25 female genital tract melanoma specimens queried, KIT mutations were detected in 4 (16.0%), NRAS mutations in 4 (16.0%), and BRAF mutations in 2 (8.0%) samples. Two of the tumors with KIT mutations harbored double mutations in the same exon. No GNAQ or GNA11 mutations were identified among 11 melanomas screened. BRAF V600E mutations were detected in 7 of 7 benign melanocytic genital nevi (100%) and 3 of 4 atypical genital nevi (75%). LIMITATIONS: Our study is limited by the small sample size of this rare subset of melanomas. CONCLUSION: KIT, NRAS, and BRAF mutations are found in a subset of female genital tract melanomas. Screening for oncogenic mutations is important for developing and applying clinical therapies for melanomas of the female genital tract.