Opening over the Coccyx (Differential Diagnosis Mass/Fistula of the Back)

Region of the buttocks from behind in a 10-month-old infant. To the right of the midline a narrow opening is visible lying somewhat caudally to the slightly prominent tip of the coccyx. The diagnosis is a dermal sinus which ends over the surface of the coccyx. The age of the patient and the normal skin surface does not fit in with a pilonoidal sinus. A dermal sinus which may be an indication for a minimal spinal dysraphism lies always above the coccyx over the sacrum and may have a connection to the spinal channel. In case of a deep coccygeal dermal sinus with a narrow opening an excision is recommended to avoid infection. In every case a histological examination is necessary because occasionally a dermoid cyst may by found at the base of the fistula. In the presented case an ependymoma of uncertain dignity was found subcutaneously.