| yolk sac tumour | An unusual and aggressive tumour of germ-cell origin that reproduces the extraembryonic structures of the early embryo. It is the most common malignant germ cell tumour found in children. It is characterised by a labyrinthine glandular pattern of flat epithelial cells and rounded papillary processes with a central capillary (schiller-duval body). The tumour is rarely bilateral. Before the use of combination chemotherapy, the tumour was almost invariably fatal. (12 Dec 1998) |
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| featureless thecal sac | <radiology> No nerve roots seen (in lumbar spine; roots not seen in T-spine) Differential diagnosis: arachnoiditis, Pantopaque, infection, haemorrhage, surgery / RT, subdural injection, contrast flows, unlike epidural injection, nerve roots seen as they exit, but not between disc levels (12 Dec 1998) |
| lacrimal sac | The upper portion of the nasolacrimal duct into which empty the two lacrimal canaliculi; empty. Synonym: saccus lacrimalis, dacryocyst, sacculus lacrimalis, tear sac. (05 Mar 2000) |
| fornix of the lacrimal sac | Fornix of the lacrimal sac; the upper, blind end of the lacrimal sac that extends above the openings of the lacrimal canaliculi. Synonym: fornix sacci lacrimalis. (05 Mar 2000) |
| fossa of lacrimal sac | A fossa formed by the lacrimal bone and the frontal process of the maxilla, lodging the lacrimal sac. Synonym: fossa sacci lacrimalis. (05 Mar 2000) |