Germ cell neoplasms which have the potentials of differentiating along somatic cell lines are regarded as teratomas. They are mature teratomas when tissues are fully differentiated and immature teratomas when primitive or immature tissue elements are present. In this retrospective study, we analyzed all the renal biopsies submitted to the Department of Pathology of the University College Hospital, Ibadan, South-West Nigeria over a thirty one year period (1981-2011). Over the period, a total of 119,986 specimens were received for histological assessment and only 1,027 (0.86%) represented kidney specimens which included all the trucut biopsies and nephrectomies. Two (0.19%) of the nephrectomy specimens from a one-year and a five-month old children were diagnosed as mature and immature cystic teratoma respectively. The sample from the one-year-old child was heavy (810 g), cystic and measured 17 x 10 x 10 cm. On microscopy, the tissues were predominantly mature neural tissue, mature skeletal muscle, cartilage and foci of normal kidney tissue while the sample from the five month old child was almost double the weight of the former (1600 g) and measured 18 x 14 x 9 cm. Cut sections revealed cystic and solid areas comprising bone, glial tissue, primitive neuroectodermal tissue, choroid plexus, immature cartilage, skeletal muscle, fat, intestinal tissue, breast structures,odontogenic and squamous epithelial tissues on microscopy.
Conclusion: Cystic teratoma is a rare occurrence in kidneys.