Summary

This study presents diagnostic histopathological features of a primary embryoid teratomatous neoplasm in the gall bladder of a 60-year-old woman, and also discusses its pathogenesis. Sections revealed immature and typical embryoid bodies and dispersed syncytial trophoblasts along with mature and immature neuroectodermal and mesodermal elements. The residual endothelial lining of the gall bladder showed in situ and proliferative changes characteristic of an endodermal tumour. Ultrasonographic and magnetic resonance imaging findings of the rest of the abdominal and pelvic organs appeared normal. Results show that the mature adult gall bladder is susceptible to primary neoplasms of a primitive nature ranging from immature embryoma and teratoma to neuroectodermal tumour. Such primitive neoplasms in adult organs where benign neuroectodermal elements are present may evolve from a constituent cell of an adult organ acquired during embryogenesis from a morula that differentiated into trophoblastic (outer) and embryoblastic (inner) cells, and existing dormant cells at rest until reactivation during oncogenesis.