Abscess or Tumor? When a Retroperitoneal Mass on Computerized Tomography Turns Out to Be a Rare Soft Tissue Growth

A retroperitoneal finding on a computerized tomography scan, in a symptomatic patient, can harbor the clinician to many differential diagnoses from infectious to malignancy. Desmoid fibromatosis (DF), a relatively innocuous mass that can spread locally, can be found in that anatomical region. Even for a rare tumor such as DF, our patient did not meet the usual benchmarks of this cancer, being an elderly female and having it appear as an abscess radiologically. Timely clinical response with radiotherapy and tamoxifen allowed our patient's DF to regress and resolved her symptoms.