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The sacrococcygeal teratoma is the most common neoplasm in neonates, with an incidence of one in 35.000-40.000 births. In ten percent of the cases this teratoma is found at the age of two years and older. The sacrococcygeal teratomas are divided in four types according to the Altman classification. Types 3 and 4 are predominantly or entirely intrapelvic. They do not necessarily have specific symptoms, which explains the delayed diagnosis. The majority of these tumors are benign, but the incidence of malignancy increases with age. Therefore early identification of the tumor and surgical treatment is necessary.

This case report describes a 58 years old patient with an asymptomatic swelling at the sacrum. After several investigations, the first conclusion was that the tumor most probably was an extra anatomic ovarian. After a complete resection of the tumor, histology revealed the correct diagnosis of a malignant sacrococcygeal teratoma.

The sacrococcygeal teratoma is a congenital abnormality rarely presented in adults. As there is a risk of malignancy, early identification and complete resection is necessary.