Orbital lymphoma, most commonly arising as a non-Hodgkin, mucosal-associated lymphoid tissue (MALT) lymphoma, is primarily seen in the elderly population. The clinical presentation is comprised of nonspecific signs - a painless palpable mass accompanied by swelling, ptosis, excessive tearing, and irritation of the eye. The diagnosis is made through the use of imaging studies, such as computed tomography and magnetic resonance imaging, whereas a surgical biopsy is necessary to confirm the exact subtype.
Orbital lymphomas, although regarded as a rare entity (encompassing only 1% of all non-Hodgkin lymphomas), are one of the most important tumors arising from the orbit, encompassing up to 25% of all tumors in certain studies   . The main locations of lymphoma within the orbit are the conjunctiva, the lacrimal apparatus, the eyelid, and the extraocular muscles  . This malignancy is principally diagnosed in the elderly population (> 60 years of age), and a strong predilection toward female gender (male-to-female ratio of 1:2.9) was observed   . The most common type of lymphoma in the orbit and the adnexa is MALT lymphoma, but various types, both low-grade and high-grade, have been described    . The clinical presentation of orbital lymphoma consists of a progressively enlarging and painless orbital mass, followed by ptosis, proptosis, eye irritation, excessive tearing, and visual disturbances . An insidious course is rather common, which is the primary reason why the diagnosis is often delayed for a significant period of time (weeks, months, or even years may pass from the appearance of symptoms)  . The importance of early recognition further lies in the fact that survival rates are estimated at 64% for 5 years and 42% for 10 years, with up to a third of patients suffering from disease recurrence .
To diagnose orbital lymphoma in its early stages, and thus significantly improve patient outcomes, the role of the physician in recognizing clinical symptoms through a detailed patient history and a meticulous physical examination is essential. The presence of ocular complaints and an orbital mass in elderly patients must prompt the physician to conduct additional tests, including a full laboratory workup (a complete blood count, liver transaminases, kidney function tests, and a peripheral blood smear) , but more importantly, imaging studies. Computed tomography (CT) and magnetic resonance imaging (MRI) are both recommended for the evaluation of orbital lymphomas   . This tumor appears as a well-defined homogeneous lesion (sometimes having a hyperdense appearance compared to extraocular muscles is observed) without the involvement of bone on both CT and MRI   . Additional MRI findings include a high signal intensity on T2-weighted images and low signal intensity on T1-weighed images, as well as high diffusion-weighted imaging (DWI) signal and low apparent diffusion coefficient (ADC) values  . In addition to CT and MRI, orbital ultrasonography has also been described as a potential diagnostic tool . A definite diagnosis and determination of tumor stage are achieved after performing a surgical biopsy and subsequent histopathological examination, together with previously mentioned imaging procedures   .