Abstract
Desmoid tumors are rare mesenchymal neoplasms that are rapidly growing but do not metastasize. We present a case of a 75-year-old man with a history of non-Hodgkin lymphoma in remission incidentally found to have an enlarging internal mammary lymph node on screening CT, subsequently diagnosed as a desmoid tumor via biopsy. The patient was deemed unfit for surgical resection and instead underwent urgent radiation and immunotherapy. This report highlights a unique case of desmoid tumor presenting as mediastinal lymphadenopathy.