Abstract

Desmoid fibromatosis (DF) is a rare tumor that arises from fibroblasts and myofibroblasts and typically presents on the trunk and limbs. While metastasis of fibromatosis is exceedingly uncommon, DF can spread rapidly to adjacent tissue. Its aggressive nature and frequent recurrence pose challenges for treatment, often requiring a multidisciplinary approach. This case represents the multidisciplinary workup for the identification and management of a rare presentation of desmoid fibromatosis involving the breast. It also discusses the post-surgical follow-up of the patient after a complex resection and reconstruction. We report a case of a patient treated at George Washington University Hospital, Washington, DC. A 26-year-old woman presented with left chest pain. Physical examination revealed an approximately 12-13 cm, ill-defined, immobile mass arising from the left breast. An MRI demonstrated a 9.5 cm spiculated mass involving the left pectoralis major muscle and underlying costal cartilage junctions. The tumor extended deep to the rib margin and along the anterior margin of the pleura. The mass was resected en bloc in a joint case with thoracic and general surgery and reconstructed with a bilateral bi-pedicled, muscle-sparing, transverse rectus abdominis myocutaneous free flap with plastic surgery. Pathology demonstrated desmoid fibromatosis. In conclusion, desmoid tumors of the breast represent a very rare breast neoplasm that can imitate other breast masses, both benign and malignant. Surgery remains an important treatment option and may require coordination and complex surgical planning between various surgical subspecialties.