Mesenteric Desmoid Tumor in a Transplant Patient

Introduction: Desmoid tumors (DTs) are deep, locally aggressive, benign connective tissue neoplasms that originate most commonly in the extremities, intraperitoneal cavity and abdominal and thoracic walls. They are rare with reported incidence of 2–4 per million population per year and account for 0.03% of all neoplasms. DTs have a high rate of local recurrence but do not metastasize. We present an unusual case of a DT found two years after kidney transplant. Case Description: 61 year-old man with end-stage renal disease due to diabetic nephropathy who underwent a deceased donor kidney transplant presents with abdominal pain starting six months after transplant. He underwent robotic inguinal hernia repair without improvement in pain. He reports night sweats, fatigue, and unintentional weight loss of 15lbs over two months. CT abdomen/pelvis showed a mid-abdomen, mesenteric soft tissue mass measuring 5.4 x 3.5 cm which was mildly hypermetabolic on PET-CT. Surgical biopsy of the mass revealed a DT. Resection of the mass was not pursued due to areas of fibrosis along the mesentery suggestive of a more diffuse process. Consequently, the oncology team started Pazopanib with good response. Discussion: The differential diagnosis for an abdominal mass is broad with high concern for post-transplant lymphoproliferative disorder. When suspecting malignancy, tissue diagnosis is always important for diagnosis and guiding treatment. For DT, asymptomatic patients can be managed with active surveillance while symptomatic patients may require surgery, systemic therapy, and/or radiation therapy.