Rare presentation of inflammatory myofibroblastic tumor in a failed renal allograft

Inflammatory myofibroblastic tumors (IMT) are rare, mesenchymal tumors that can occur in any anatomic location. IMTs have a variable clinical course but usually require wide surgical excision to prevent local recurrence. There have been limited case reports of IMT occurring in solid organ transplant recipients. Herein we report on a case of IMT presenting in a failed renal allograft. A 53-year-old male awaiting re-transplant presented with pain and a palpable mass in his allograft. Imaging demonstrated an infiltrative soft tissue mass encasing the renal hilum. Percutaneous biopsy demonstrated a myofibroblastic proliferation with myxoid background and no high-grade features. The tumor cells were diffusely positive for anaplastic lymphoma kinase-1 (ALK-1) and had a Ki-67 proliferation index of 10%. These findings were consistent with a diagnosis of IMT. A transplant nephrectomy was performed with wide margins to achieve an R0 resection. Pathology on the resection specimen confirmed an IMT that measured 6.5 cm x 6.3 cm. The patient has no evidence of local recurrence at 6-months follow-up and has been relisted for a second kidney transplant.