Nodular fasciitis growing at the port site of robotic surgery for rectal cancer

Background Nodular fasciitis (NF) is a type of rare and rapidly growing tumor that affects the muscular fascial layers. Due to its locally aggressive nature and rapid growth, NF can be mistaken as a malignant process on either clinical or histological grounds. Case presentation A 61-year-old man was affected by rectal cancer. We performed a robotic, high-anterior resection with lymph node dissection. According to the 8th edition of Union for International Cancer Control, the diagnosis was stage I pT2N0M0. During a routine follow-up 1.5 years after the robotic surgery, a computed tomography examination revealed a tumor in the upper right abdominal wall, at the site of the surgical port, that measured 45 mm. Magnetic resonance imaging indicated a hypo-intensive mass within the right straight muscle of the abdomen. Port site recurrence following the robotic surgery for rectal cancer was suspected, and an ultrasound-guided fine-needle aspiration was performed; it revealed a low-grade myofibroblastic tumor or benign neoplasm, but was inconclusive. We performed an excision of the lesion, and histopathology confirmed NF, seen as a solid, nodular, spindle-cell lesion. The patient was postoperatively followed for more than 1 year without any sign of recurrence of either cancer or NF. Conclusions NF is histologically benign, but local recurrence frequently occurs. We encountered a patient with NF at the port site after robotic surgery for rectal cancer.