211 © Springer Nature Singapore Pte Ltd. 2019 S. Amrith et al. (eds.), Ocular Adnexal Lesions, https://doi.org/10.1007/978-981-13-3798-7_39 T-Cell Lymphoma Gangadhara Sundar, Stephanie Ming Young, Poh Sun Goh, Bingcheng Wu, Min En Nga, and Shantha Amrith Introduction Orbital neoplasms are not uncommon. The vast majority are benign lesions that may present either in children or adults. The most common primary malignant neoplasms of the orbit are lymphomas. Most lymphomas of the orbit and adnexal region are B-cell lymphomas with mucosa-associated lymphoid tissue (MALT) being the most common. T-cell lymphomas are extremely rare and when present may be a manifestation of known preexisting systemic disease. They arise primarily from the paranasal sinuses, more commonly in East Asians. While B-cell lymphomas are usually well recognized and more easily treated, T-cell lymphomas often carry a guarded prognosis. Clinical Scenario A 55-year-old East Asian male presented with a lump in the inner corner of the right eye of a few months’ duration. He did recall generalized weakness and weight loss over the past sev- eral months, but without fever, night sweats, nasal obstruction, epistaxis or any visual symptoms. He had no known previous systemic disease. Ophthalmic examination at presentation revealed normal visual acuity in both eyes. Examination of the left eye and adnexa were within normal limits. On the right, while the globe and intraocular examination were unremark- able, there was a frm injected subconjunctival lesion of the medial canthus, without tenderness, reducibility or compress- ibility (Fig. 39.1). There was no proptosis. Evaluation of the lacrimal drainage system and a transnasal endoscopic exami- G. Sundar · S. M. Young · S. Amrith (*) Department of Ophthalmology, National University Hospital, Singapore Department of Ophthalmology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore e-mail: gangadhara_sundar@nuhs.edu.sg; stephanie.young@nuhs. edu.sg; shantha_amrith@nuhs.edu.sg P. S. Goh Department of Diagnostic Imaging, National University Hospital, Singapore Department of Diagnostic Imaging, Yong Loo Lin School of Medicine, National University of Singapore, Singapore B. Wu Department of Pathology, National University Hospital, Singapore M. E. Nga Department of Pathology, National University Hospital, Singapore Department of Pathology, Yong Loo Lin School of Medicine, National University of Singapore, Singapore 39 Fig. 39.1 Clinical picture showing the medial conjunctival mass in the right eye