We report the case of a 37-year-old Japanese man who presented with a left lower abdominal mass that was initially interpreted clinically as an inguinal hernia. The patient reported a swelling in his left lower abdomen over the past 6 months. Magnetic resonance imaging revealed a left inguinal mass extending from the left spermatic cord to the left inguinal subcutaneous layer. Local excision was performed, with a preoperative diagnosis of benign soft tissue tumor. Histopathological diagnosis revealed aggressive angiomyxoma (AAM), and no recurrence was observed 6 months after surgery. AAM is a rare tumor which most commonly occurs in the pelvis or perineum of premenopausal women, with extremely rare cases in men. The findings from previously reported cases and our case suggest that AA...