LAUSR

A 12-year-old boy presented to the dermatology inpatient consultation service with a 2-month history of a rapidly growing mass on the right leg after a fall. He reported night sweats, but denied any fevers, chills, weight loss or other lesions. One month prior, the patient attended the emergency department, where the mass had been managed as a presumed abscess with oral cephalexin and incision and drainage. He had initial improvement but subsequent rapid worsening. Examination revealed a 10 11 cm indurated red-purple tumor with well-demarcated brownish edges located on the right medial calf (Figure 1). There was no lymphadenopathy. A complete blood count and comprehensive metabolic panel were unremarkable. Ultrasound, radiograph and computed tomography (CT) of the leg showed a subcutaneous swelling with no underlying muscle or bone abnormality. A punch biopsy of the nodule was performed (Figure 2). Immunohistochemistry revealed positivity for CD4, CD56 (Figure 3), CD123 (Figure 4), and TCL1A, among others.