Although only 3% of ovarian teratomas are immature, they account for almost 20% of primitive germ cell tumours and for 10-20% of ovarian cancer in the first two decades, the age group in which these tumours typically occur.14 There is usually a palpable abdominal or pelvic mass, frequently accompanied by pain. Rarely, an immature teratoma is preceded by an ipsilateral dermoid cyst that was resected months to years previously; the risk of an immature teratoma in such patients may be increased if the dermoid cysts are bilateral, multiple, or associated with rupture. 5,6 Two-thirds of the patients with immature teratomas have an elevated serum level of alpha-fetoprotein (AFP) at presentation, although the levels are usually lower than those encountered in patients with yolk sac tumours. 7-9 Occasional patients have had an elevated HCG, sometimes associated with sexual pseudoprecocity. 1~ As many as one-third of the tumours have extraovarian spread at the time of operation, usually in the form of peritoneal implants, less commonly nodal metastases, and rarely, hematogenous metastases. 24,8,1~ The risk of extraovarian implants may be increased in tumours that have ruptured or those with adhesions. 11,12 are frequently present, and rarely, one or more large cysts occupy most of the specimen. Grossly evident dermoid cysts can be identified in approximately 25% of cases. 6 The solid areas, which are usually predominantly composed of neural tissue, are typically soft, fleshy, and gray to pink, and may be focally haemorrhagic or necrotic. Areas of bone and cartilage may be visible or palpable. Bilateral involvement is very rare in the absence of extraovarian spread, but the opposite ovary harbours a dermoid cyst or less often another benign tumour in approximately 10% of the cases. 6 The sine qua non for the diagnosis of immature teratoma is the presence of at least some immature tissue resembling that of the normal embryo; the amount of such tissue varies from rare loci to a predominant component. Most or all of the immature tissue is immature neuroectodermal tissue (Fig. 1), usually in the form of neuroepithelial rosettes and tubules, cellular foci of mitotically active glia, and in occasional cases, small areas resembling glioblastoma or neuroblastoma. The neuroepithelium may be pigmented. Immature or embryonal epithelium of various types, both ectodermal and endodermal, including hepatic tissue, 8,9,13 as well as immature mesenchymal elements, such as cartilage and