Abstract
Glomus tumors are typically benign, soft tissue neoplasms composed of thermoregulatory glomus bodies. The more common varieties, such as subungual, are treated surgically and typically have a very low mortality rate. Malignant glomus tumors are very rare, and their pathogenesis is poorly understood. As such, treatment options and prognosis are unclear. We present a 67-year-old female diagnosed with a chest wall glomus tumor with biopsy-proven metastases to her lungs. Her treatment course included neoadjuvant radiation therapy followed by immunotherapy with pembrolizumab. After completion of the initial radiation therapy, imaging showed disease regression. Interval imaging after seven months of immunotherapy showed the resolution of all lung nodules with no reported concerns for disease recurrence. Pembrolizumab was discontinued due to concerns for dermatologic and renal adverse events, and the patient continues to be monitored off therapy. The metastatic glomus tumor described in this case had several unique qualities, including its initial presentation on the chest wall as an aggressive lesion, as well as its spread to multiple locations in the lungs. Glomus tumors are not normally as aggressive as seen in this case, but the genetic profile with high tumor mutational burden allowed for guided treatment. Radiation is often used as neoadjuvant treatment in higher risk glomus tumors, but the addition of immunotherapy such as pembrolizumab represents a potential avenue to manage these patients when surgery is not an option. Malignant glomus tumors are exceptionally rare occurrences that, by nature of their rarity, require protocols or therapies that are not specifically designed for their treatment. The clinical course of these tumors is difficult to predict as most cases of metastatic spread have few examples from which to draw conclusions. This case provided encouraging results for treatment with radiation and, potentially, immunotherapy. Each instance of a malignant glomus tumor and its genetic profile should be closely examined and documented so that sufficient data can be accumulated to guide treatment for this rare cancer.