INTRODUCTION: Postoperative spindle cell nodules are benign and reactive lesions that occur at the previous surgical site. It often develops like a sarcoma and is resected via highly invasive procedures. To date, there have been no published reports on the natural progression of postoperative spindle cell nodules without surgical intervention. CASE: A 45-year-old woman underwent a total abdominal hysterectomy for leiomyoma. A 5-cm pelvic mass exposed in the vaginal stump developed 7 weeks later, causing genital bleeding. Positron emission tomography-computed tomography revealed a pelvic mass and an enlarged pelvic lymph node with high uptake. We suspected an invasive sarcoma in the pelvis. However, through a transvaginal needle biopsy, the mass was diagnosed as a postoperative spindle cell nodule posthysterectomy. The nodule slowly reduced in size and completely disappeared 9 years posthysterectomy. CONCLUSIONS: Correct diagnosis of this nodule with sarcomatous onset based on biopsy was important to avoid unnecessary surgeries. The lesion completely disappeared spontaneously after long-term follow-up.