Differential diagnosis The differential diagnosis of a cystic, predominantly external, tumour (Type l) should include a meningomyelocoele: however, the absence of intracranial abnormalities should exclude the diagnosis. In the case of cystic intra-abdominal tumours there is a wide differential including ovarian cysts, haematometra, duplication cysts (see Chapter 11) and an anterior meningocoele.A recent report has documented a neuroectodermal cyst mimicking an intra-abdominal sacrococcygeal 54 teratoma.