[Glomangiomatosis of uncertain malignant potential: a clinicopathological and genetic analysis]

Objective: To investigate the clinicopathological features, genetic characteristics, and differential diagnosis of glomangiomatosis with uncertain malignant potential. Methods: Two cases of glomangiomatosis with uncertain malignant potential were collected at Henan Provincial People's Hospital from 2013 and 2023. Immunohistochemistry and next generation sequencing (DNA-seq) were used to detect the related protein and gene variation. Patients were followed up. Results: Case 1 was male, 34 years old; and case 2 was female, 28 years old. Both had tumor recurrence in the original site. There were multiple nodules at right calf and ankle, involving superficial subcutaneous tissue and deep interfascicular muscles; some nodules were borderless and painful. Microscopically, the tumor was nodular with fibrous pseudocapsule, some had indistinct borders and diffuse infiltration to the surrounding adipose tissue. The tumor cells were round to ovoid with inconspicuous nucleoli, partly surrounding small irregularly dilated thin-walled blood vessels. The recurrent tumors showed epithelioid morphology in some of the tumor cells, with eosinophilic cytoplasm, some apparent nucleoli, mild to moderate nuclear atypia, and brisk mitotic figures. Focally, perimuscular cell differentiation was noted. The small lesion showed intravascular tumor thrombus. NGS revealed BRAF V600E mutation in case 1, and BRAF V600E mutation combined with PDGFRB gene amplification in case 2. Conclusions: Glomangiomatosis with uncertain malignant potential is a rare variant of glomus tumor. It has a unique growth pattern morphologically, BRAF V600E mutation, and invasive biological behavior.