Wegener's granulomatosis (WG) is an autoimmune disorder characterized by necrotizing granulomas involving mainly the upper-lower respiratory and renal tracts, albeit a potentially life-threatening involvement of other body parts is not rare. Furthermore, there are several reports accounting for an increased risk of solid malignancies due to the autoimmune disease per se, or the immunosuppressive therapies. Among treatments, radiotherapy could be a therapeutic option as proven by its use in typical WG lesions such as solitary granulomas or subglottic stenosis, successfully treated with low radiation dose. Herein, we report a case of squamous cell carcinoma of the glottis-subglottic larynx, T3 N0 M0 stage, occurring in a patient with a long-standing WG, heavily treated in the past with cyclophosphamide and rituximab, who achieved a complete response of the tumor using a low-dose radiation therapy and no concurrent chemotherapy. The hypothesis is that this cancer probably arose from a subglottic stenosis as a late manifestation of WG and exhibited more radiosensitivity than a naïve tumor. If so, solid tumors occurring on granulomas within an autoimmune disease course should be treated with a lower radiation dose.