A NEW ERA: TARGETED THERAPY FOR RECURRENT GLOMUS TUMOR

Background: Glomus tumors (GT) are rare, vascular, benign soft tissue neoplasms that are composed of cells resembling modified smooth muscle originating from glomus bodies. Glomus bodies are specialized forms of arteriovenous anastomosis found in the reticular dermis that serve as thermoregulators. These glomus bodies are highly concentrated in the hands and feet, and thus, GT typically present as solitary lesions in the subungual region but may also occur elsewhere in the skin and soft tissues. Classically, GT are diagnosed with the following triad of symptoms: focal tenderness, spontaneous pain, and temperature sensitivity. Total surgical excision remains the mainstay of treatment. Here, we describe an atypical case of multifocal GT resistant to surgical excision and discuss alternative treatment modalities for recurrent cases in a pediatric patient. The treatment of recurrent GT remains a challenge due to lack of literature supporting alternative options. Management is especially difficult following a series of failed surgical excisions. Our objective is to explore the efficacy of non-surgical targeted-therapy treatment for recurrent GT based upon molecular genetic findings. Case Information: A 16-year-old female with a history of multifocal GT status post prior extensive removal through medial and lateral incisions in 2012, 2013, and 2015 presented back in 2021 with significant pain and swelling of the right lower extremity. History and PET Scan imaging confirmed extensive recurrence where the prior neoplasms had been present. Specifically, PET Scan demonstrated multifocal uptake within numerous masses in the right calf and ankle. Molecular genetic testing of GT in this patient revealed genomic changes in the platelet-derived growth factor receptor gene (PDGFRβ- R561_E563>Q). This gene transcribes platelet-derived growth factor receptor beta (PDGFRβ), which is part of a family of proteins called receptor tyrosine kinases. Accordingly, the patient started Sunitinib, a multi-receptor tyrosine kinase inhibitor which decreases phosphorylation of PDGFRβ and subsequently inhibits proliferation and survivability. Initially, treatment was intermittently held due to side effects of syncope, rash and plantar erythrodysesthesia. Nevertheless, as a result of improvements in pain and size of the tumors, she resumed treatment at a lower dose. Following trials of two dose reductions, she tolerated the medication well with resolution of side effects. The patient continued to note a decrease in the size of her GT, confirmed by imaging and her ability to return to work successfully. Conclusions: This case highlights the insufficiency in current mainstay treatment options of GT with surgical excision. Our findings emphasize the significance of incorporating molecular genetic testing into the treatment and management of recurrent GT to prevent disease relapse. Further research into alternative gene therapies is warranted.