A 10-year-old girl presented with a one-year history of a slow-growing, posterior neck mass. MRI (Picture 1) showed a 6-cm soft tissue mass deep to the trapezius muscle in the upper cervical region posteriorly, centered to the left of midline. It had predominant fat signal with multiple septations. She underwent excision of the mass, which yielded a well-circumscribed, lobulated fatty lesion with white fibrous bands (Picture 2). Microscopy is shown in Pictures 3–5.
Narges Jahanseir, M.D.
Resident, Surgical Pathology
Karen Fritchie, M.D.
Consultant, Surgical and Medical Pathology
Professor of Laboratory Medicine and Pathology
Mayo Clinic College of Medicine and Sciences