This report describes a case of sacrococcygeal teratoma with adenocarcinomatous
transformation in a 45-year-old woman. This is an infrequent location for teratoma in adults and
malignant transformation has rarely been described. Prognosis depends on complete excision.
Clinical manifestations, imaging aspects and histological findings of this case are presented. CT
and MRI adequately document the mixed cystic and solid nature of the tumour, its extension and
relations with adjacent structures, allowing accurate pre-operative planning