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Background
Lymphomas are malignant neoplasms of the lymphocyte cell lines. They mainly involve lymph nodes, spleen and other non-haemopoietic tissues. Lymphoproliferative disease in the orbit has diverse clinical manifestation. The most substantial clinical issue is to recognise the lymphoproliferative disease and differentiate it from other orbital inflammatory lesions. Initially the two diseases may have common disease manifestation including imaging studies. 1 Orbital lymphomas represent 8-10% of all extra-nodal NHL, and only 1% of all lymphomas. 2-4 Primary orbital peripheral T-cell lymphoma is an exceedingly rare neoplastic disorder. 5 Orbital lymphoma presents as slowly enlarging lesions arising from the eyelid, orbit, lacrimal gland or conjunctiva. 6
Case presentation
A 6-year-old child presented with complaints of gradually progressive proptosis and lagophthalmos ( figure 1 ) for 3 months associated with fever for 15 days. There was no significant loss of vision. Ophthalmological examination disclosed a left orbital mass, developing outside the eye displacing the globe inferolaterally. Uncorrected visual acuity was 6/12 in both eyes. No organomegaly or lymphadenopathy was present. The family history was non-contributory.
Orbital CT scan disclosed a large left orbital extra-conal homogenous mass along superior and medial orbital wall measuring 33x18x30 mm without evidence of any bone destruction. There was marked displacement of globe inferolaterally along with dehiscence of inferior wall of the bony orbit. The right orbit and both the globes were otherwise, normal.
In view of orbital mass lesion, a CT-guided biopsy measuring 0.75x0.5 cm was taken. The microscopic examination of the tissue showed polymorphous population of cells consisting of dense lympho-histiocytic infiltrate harbouring atypical lymphocytes. The atypical cells were small to medium in size, having high nucleo-cytoplasmic ratio, irregular cleaved nuclear contours, condensed chromatin and scant cytoplasm ( figure 2 ). These cells were accompanied by plasma cells, eosinophils and conspicuous proliferation of small vascular channels with plump endothelial cells and frequent mitotic figures. A diagnosis of non-Hodgkin's lymphoma (NHL) was rendered and immunohistochemistry was performed for exact typing of the tumour.
Immunohistochemical stains for LCA (leucocyte common antigen) (CD45), CD45RO, CD3 were positive ( figure 3 ), suggesting a lymphoid neoplasm of T-cell origin. The neoplastic cells were negative for CD15,...