A case of pilonidal disease presenting as a subcutaneous nodule in the peri-umbilical area

A 25-year-old fireman presented with a 3-week history of pain arising from the umbilicus to the right side of the umbilicus. Examination revealed hirsute abdomen and a solid subcutaneous nodule (diameter, 3x2 cm) on the right side of the umbilicus. Ultrasonography showed an iso-hypoechoic mass, and computed tomography revealed an obscure mass. Excisional biopsy of the mass showed a yellowish-white solid mass with a strand of hair. Histopathological test revealed granulomatous inflammation around the hair shaft. On the basis of these findings, a diagnosis of pilonidal disease presenting as a subcutaneous nodule in the peri-umbilical area was made. Pilonidal disease should be considered in the differential diagnosis of umbilical nodules that might develop in young, hirsute men.