Micro-GIST with BRAF mutation arising in a Leiomyoma: a rare case report and literature review.

[BACKGROUND] Gastrointestinal stromal tumors (GISTs) are the most common soft tissue tumors of the digestive tract, originating from the interstitial cells of Cajal (ICCs). They are typically characterized by mutations in KIT or PDGFRA genes. However, a subset of GISTs lacks these mutations and has been associated with alternative molecular events. This study presents a case of micro-GIST with a BRAF mutation within a leiomyoma, a rare occurrence with only one previous case reported in the literature involving a C-KIT mutation.

[CASE PRESENTATION] A 60-year-old female patient was diagnosed with a gastric submucosal tumor following gastroscopy and upper abdominal ultrasound examinations. The tumor, measuring 1.6 cm × 1.2 cm, was resected via laparoscopic wedge resection. Histological examination revealed a region within the tumor with higher cell density and distinctive cytological features, consistent with GIST. Immunohistochemical analysis confirmed an ICC-like phenotype in this region. NGS identified a BRAF mutation in the dense intermediate cells, while no mutations were found in the surrounding typical leiomyoma region. The patient remained in a satisfactory condition post-surgery.

[CONCLUSIONS] This case report describes the first documented micro-GIST with a BRAF mutation arising in a leiomyoma, highlighting the importance of molecular detection in the differential diagnosis of GISTs.