An 8-year-old male presented to his pediatrician for new onset right neck mass. He recently had a viral upper respiratory infection, and during this illness the mass became apparent. He was referred to pediatric hematology and oncology out of concern for malignancy. On further history, he denies fever, unintentional weight loss, or night sweats. His exam is notable for a mobile, tender, soft tissue mass measuring 2x3cm on the lower left neck. Range of motion was not inhibited. Overlying skin has a normal appearance. Ultrasound revealed a 3.0 x 1.1 x 2.6 cm complex subcutaneous lesion concerning for a vascular malformation. Complete blood count was unremarkable, LDH and uric acid were normal, d-dimer was 256 mg/ml (normal <500 mg/ml), fibrinogen 262 (normal >150 mg/dL), PTT 30 seconds (normal 24 seconds-32 seconds), and PT 14.5 seconds (normal).