Lesión pilosa dolorosa en región sacrocoxígea Translated title: Painful hairy lesion in the sacrococcygeal region

Abstract Introduction: Neoplastic degeneration is an uncommon but extremely serious complication of pilonidal sinus (PS) disease. We pretend to determine the factors that influence in the prognosis of the neoplastic disease assessing clinical features and histological findings. Materials and Methods: We retrospectively studied the patients diagnosed of malignization of PS in our institution from 2000 to 2019. Results: Seven male patients with a mean age at diagnosis of 64.8 years old were collected. Average time between the initial symptoms of PS disease and the tumor diagnosis was 33.7 years. The patients presenting an ulcerative pattern in the primary tumor showed in all the cases perineural invasion, local deep structures infiltration, and neoplastic dissemination to the regional lymph nodes. All these patients died in an average time of 7 months. On the other hand, patients with exophytic patterns in the primary tumor did not present local invasion or regional nodes affectation. All the cases survive with an average follow-up of 70.5 months. Conclusions: Ulcerated lesions clearly show a worse prognosis than tumors with exophytic morphology. Factors as perineural infiltration, local deep structures infiltration, or regional lymph node involvement dramatically decrease survival rates.