We report the case of a 41-year-old man with an epidermoid carcinoma that had developed on a meningocele with a fistulous tract that chronically drained cerebrospinal fluid. After a review of the literature, we discuss the cause of this rare occurrence. We think that the recurrent discharge of spinal fluid (never complicated by meningitis) may have caused a chronic irritation of the tissues and then the delayed development of a carcinoma, which is similar to a case found in the literature. In our case there was a “flow” of carcinomatous cells along the fistula, which entered the meningocele, invading the subdural space as far as the peduncle. Our patient, who had a benign lesion (meningocele), came under neurosurgical care only after the lesion had degenerated. The malignant degeneration of such a benign lesion emphasizes the need for surgical treatment as soon as possible.