- Usually in close proximity to joints and tendon sheaths
- Extremely rare in veterinary medicine c.f. humans
- No consensus as to genesis
- Cysts contain mucinous/yellow fluid
More about ganglion cysts:
[Ganglion cysts in a juvenile dog. Cho K-O et al. Vet Path (2000) 37 340-3]
Ganglion cysts:
- Usually in close proximity to joints and tendon sheaths
- Extremely rare in veterinary medicine c.f. humans
- No consensus as to genesis
- Cysts contain mucinous/yellow fluid
- Wall composed of: inner myxomatous and outer
- Inner myxomatous areas
- Pleomorphic stellate and spindle cells within an abundant myxoid stroma
- Lined by fibroblasts on the inner aspect (although no true lining cells)
- Outer fibromatous areas
- Similar to granulation tissue
- Mitoses rare
- Inner myxomatous areas
- The base of all ganglion cysts in contact with the bone, with no boney destruction
- Mucin in the cavities stains blue with acid mucin and with AB-PAS
- EM
- Abundant rough ER and golgi and few mitochondria in the inner myxomatous cells and various stages of myxoid metaplasia
- Cells resemble both synovial cells and fibroblasts
- Small numbers of degenerative ganglion cells in the inner myxomatous lesions – marked dilation of rER and golgi; filopodia, multiple small vacuoles containing a dense granular material in the cytoplasm
- ECM – bundles of collagen fibrils adjacent in the fibroblasts in the initial phase of the mucinous lesions -> collagen fibrils broken and shortened and haphazardly arranged
- No communication with the synovial cavity and no synovial lining so not synovial cysts or adventitious bursa
- Cysts develop within the mucinous lesions surrounding a central collagenous core
- Synovial cells have two appearances on EM:
- Type A cells – phagocytic, contain numerous vacuoles, branched aperiodic fibrils, filopodia, vesicles, mitochondria
- Type B cells – adapted for protein production and contain abundant rER, few mitochondria, occasional vesicles and vacuoles
- Cells in the ganglion walls are similar to type B cells and fibroblasts
- Mucin probably produced by metaplastic fibroblasts