Clinicopathologic features of gastric glomus tumor: A report of 15 cases and literature review

Objective: Glomus tumor is a relatively uncommon soft tissue neoplasm predominantly occurring in upper extremity (fingers), less reported in stomach. This study aimed to discuss the clinicopathologic features of gastric glomus tumor (GGT) and then provide reference for clinical practice.Methods: A retrospective analysis of all cases pathologically diagnosed of GGT was performed, pathological findings were correlated with clinical information, immunohistochemical studies, next-generation sequencing, and patient follow-ups. A review of literature by searching similar cases was conducted to summarize previous knowledge of GGTs.Results: Our study identified 15 GGTs included 5 males and 10 females, aged between 35-75 years old (median, 49 years old). The tumor was located to the gastric corpus in 6 cases (40%) and to the antrum in 9 cases (60%). The maximum tumor diameter ranged between 1-4 cm (median, 1.5 cm). There were 11 cases (73%) of solid glomus tumor, 3 cases (20%) of mixture of solid glomus tumor and glomangioma, and 1 case (7%) of glomangiomyoma. Partial spindle cell area was observed in 3 cases (20%), moderate cellular atypia in 1 case (7%), atypical mitosis in 1 case (7%), vascular invasion in 5 cases (33%), neural invasion in 6 cases (40%) and tumor necrosis in 1 case (7%). Tumor cells expressed Collagen type IV, alpha-smooth muscle actin (alpha-SMA), and synaptophysin in most cases. The Ki67 index varied from 1% to 30%. Next-generation sequencing reported EGFR, PIK3CA, KEAP1 and TP53 mutation. The outcome information was obtained in 12 (80%) cases, followed for 6-63 months, 11 patients (92%) had tumor-free survival and 1 patient (8%) developed liver metastasis 26 months after surgery. Literature review obtained 16 previously reported malignant GGT cases. In terms of the total 31 cases, univariate analysis revealed that the atypical mitosis (OS: p = 0.009; DFS: p = 0.010) and severe cellular atypia (OS: p = 0.007; DFS: p = 0.004) were significantly associated with poor prognosis (patient death).Conclusion: GGT is indolent, while long-term close follow-up should be required in the presence of increasing number of risk factors. Malignant GGT is relatively uncommon and predisposes to liver metastasis, calling for accumulation of large-sample data and experience.