Orbital Solitary Fibrous Tumour (SFT) is an uncommon benign spindle cell tumour with characteristics of mesenchymal fibroblast- like cells. It was originally recognised in the pleura. It is also seen in peritoneum, mediastinum, deep soft tissues of extremities, and conjunctiva as well.
Orbital solitary fibrous tumour in orbit may involve intraconal or extraconal compartment, lacrimal sac, lacrimal gland fossa, and eyelids. Orbital SFT was misdiagnosed until its characteristic features, particularly strong and diffuse immune-reactivity to CD 34 (cluster of differentiation 34 is a marker for primitive blood and bone marrow derived progenitor cells) was described. It is possible that orbital SFTs were under diagnosed earlier because of its rarity in extra-pleural sites and histological similarity to other spindle-cell tumours.
WHO in 2002 considered that SFTs, haemangiopericytomas, and giant-cell angiofibromas, represent a spectrum of spindle-cell neoplasm, rather than distinct pathologic entities.
References
Lee WR. Ophthalmic Histopathology Second Edition. Springer-Verlag London 2002. P 388.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3263171/
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4732263/
http://eyewiki.aao.org/Solitary_fibrous_tumor
http://www.ajnr.org/content/29/5/857
SFT most commonly presents in middle-aged patients with symptoms such as
It is usually not associated with features of pain or entrapment of nerves.
Recurrent tumours often invade surrounding soft tissue or bone, with possibility of spread into nasal sinuses or cranial cavities.
Orbital solitary fibrous tumour is an uncommon benign spindle cell tumour with ultra structural and immuno-histochemical characteristics of mesenchymal fibroblast like cells.
SFTs are presumed to arise from pluripotent mesenchymal stem cells that have the capacity to differentiate along endothelial, pericytic, or fibroblastic phenotypes, similar to normal angiogenesis. This may explain the presence of the characteristic haemangiopericytoma like vessels. Currently, there is no stain to identify specific lineage such as pericytic origin.
Orbital solitary fibrous tumour is unilateral and occurs in both adults and children. Patient generally presents with proptosis and displacement of eyeball due to mass effect. It usually show slow clinical course without vision loss or significant pain. It may occur supero-temporally and may simulate lacrimal gland tumour. It may simultaneously involve orbit and nasal cavity. Occasionally, SFT may be aggressive and can extend to the central nervous system. Malignant transformation and metastasis are rare.
Histopathology:
Histopathologically, morphology of SFTs varies from highly cellular vascular lesion to fibrous areas with less number of cells. Fibrous matrix contains broad bands of collagen. Characteristic haemangiopericytoma like vascular branching, which is characterised by bifurcating dilated blood vessels with perivascular fibrosis, may be present. There is poor correlation between morphology and malignant potential.
In most SFTs, immuno-histochemistry shows an intense reactivity for vimentin (protein seen in cells derived from mesenchyme), CD34 and CD99.
Imaging studies:
Differential diagnosis
SFT needs to be differentiated from
Complete surgical resection is the treatment of choice. Incomplete removal increases the risk of clinical recurrence of tumour. Therefore, close follow up is required in cases with suspected residual tumour. Adjunctive radiation therapy is used in highly cellular lesions.
Recurrent tumours may show features of malignancy and may metastasise.
