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Synovial sarcoma is a malignant mesenchymal tumour, which makes up to 10% of all soft tissue sarcomas. It most often affects young adults and is commonly found in periarticular sites of the extremities. It may occur at other locations, including head and neck, heart, abdominal wall, mediastinum, and lung. Synovial sarcomas of the head and neck are rare, making up only 10% of all synovial sarcomas, and typically localising to the hypopharynx or parapharyngeal space. We report a first case of primary monophasic synovial sarcoma of the conjunctiva in a 29 year old man with no significant medical history, who developed an enlarging conjunctival lesion at the medial canthus of the right eye.
A 29 year old man presented with a 4 month history of a growing mass in the conjunctiva at the medial canthus of the right eye. Gross appearance was of a pink, fleshy, soft tumour, 10 mm in diameter, with a prominent feeding blood vessel (Fig 1). There was no significant past history, in particular, no apparent risk factors for acquired immunodeficiency or history of previous orbital irradiation. Ophthalmic examination showed no visual deficit. Computed tomograph (CT) scan showed no deep extension of the mass. General examination and CT staging of potential primary and metastatic tumour sites showed this to be a solitary lesion.
At surgery the tumour was found to be adherent to the medial rectus muscle and was excised with close margins. Excision was macroscopically complete, and the appearance was of a 1 cm diameter soft tissue lesion, vascular and without necrosis. Histology showed a spindle cell tumour with collagen bundles and frequent vessels in the stroma (Fig 2). Immunohistochemistry showed widespread EMA staining and scattered keratin positive cells. Stain for CD-99 and bcl-2 was positive. These are characteristic features of a monophasic synovial sarcoma. Stain for S-100 was also positive, which is a feature observed in one third of these tumours. Blocks were referred to an international sarcoma pathology reference centre.
There has been a significant recent rise in the reporting of ocular and ocular adnexal sarcomas. Almost all cases are associated with acquired immunodeficiency syndrome (AIDS), and irradiation of the orbits of children with hereditary retinoblastoma. Adult Kaposi’s sarcoma and childhood leiomyosarcoma are increased more than 10 000 fold with AIDS.1 Hereditary retinoblastoma shows increased risk of sarcomas in the path of radiotherapy beam, especially if the patient is irradiated below 1 year of age.2
Synovial sarcoma is not of synovial origin, but is thought to be derived from as yet unknown multipotent stem cells capable of differentiating into mesenchymal and/or epithelial structures. It may be biphasic (consisting of epithelioid cells admixed with spindle cells) or monophasic (spindle cells with little or no evidence of epithelioid differentiation). Synovial sarcoma is associated with the chromosome translocation t[x;18][p11.2;q11.2] causing a transcribed fusion product of two genes, SYT and SSX1, or SSX2. Diagnosis may be confirmed by fluorescence in situ hybridisation (FISH) or polymerase chain reaction (RT-PCR).3
Although primary orbital synovial sarcoma,4 and primary biphasic synovial sarcoma of the orbit5 have been reported, we can identify no cases of a primary monophasic synovial sarcoma presenting as a conjunctival tumour. Other soft tissue sarcomas may present as a primary tumour of the conjunctiva, including malignant fibrous histiocytoma of the conjunctiva,6 and primary conjunctival rhabdomyosarcoma.7 Benign leiomyoma of the caruncle8 and leiomyosarcoma of the conjunctiva have been reported,9 as has conjunctival liposarcoma.10
Complete surgical excision is the only curative option for adult soft tissue sarcomas. Adjuvant postoperative radiotherapy may reduce the risk of local relapse. Paediatric soft tissue sarcomas may respond to cytotoxic chemotherapy, but this is unusual in adult lesions. For soft tissue sarcoma of the conjunctiva, surgical adjuvant treatment with superficial radiotherapy (strontium-90) has been reported.7
Although rare, primary synovial sarcoma should be considered in the differential diagnosis of conjunctival masses.
We thank Professor C D M Fletcher, director of surgical pathology, Brigham and Women’s Hospital, Boston, MA, USA for his advice.