Conjunctival lymphoma is a rare cancer originating in the conjunctiva, the clear membrane covering the white part of the eye and the inner surface of the eyelids. This condition is categorized as an ocular adnexal tumor, affecting the tissues surrounding the eyeball. Although malignant, conjunctival lymphoma typically follows an indolent, slow-growing course compared to many other cancers. The disease often presents as a localized mass, making identification important for maintaining eye health.
Understanding Conjunctival Lymphoma
This condition is classified as a non-Hodgkin lymphoma, arising from the uncontrolled proliferation of immune cells known as B-lymphocytes. The vast majority of cases are the extranodal marginal zone B-cell lymphoma subtype, commonly referred to as Mucosa-Associated Lymphoid Tissue (MALT) lymphoma. This MALT subtype accounts for approximately 80% of all conjunctival lymphomas. The conjunctiva naturally contains lymphoid tissue that responds to foreign substances, and MALT lymphoma is thought to be a malignant transformation within this system.
The precise cause remains under investigation, but the disease is often associated with chronic inflammation or autoimmune conditions. Autoimmune disorders such as Sjögren’s syndrome and Hashimoto’s thyroiditis are potential risk factors. Researchers hypothesize that persistent antigenic stimulation, potentially from infectious agents like Chlamydia psittaci, may trigger the chronic immune response leading to B-cell transformation. The condition most frequently affects individuals in their fifth to seventh decade of life and shows a slight predominance in females.
Identifying Physical Signs
The most distinctive clinical finding is the characteristic “salmon patch” on the eye surface. This describes a painless, fleshy, pink-to-red mass that appears beneath the conjunctiva, often in the fornix or lower eyelid. The color results from the dense accumulation of abnormal lymphocytes visible through the transparent membrane. Since the lesion is painless and grows slowly, many patients experience a significant delay in seeking medical attention, sometimes up to eight months after onset.
Patients may also experience non-specific ocular complaints, including chronic irritation, a persistent foreign body sensation, and excessive tearing. Generalized redness of the eye that does not resolve with typical treatments can also indicate underlying conjunctival infiltration. In rare instances where the mass is large or extends into the orbit, it can cause the eye to protrude (proptosis) or restrict eye movement, potentially leading to double vision.
Confirmation Through Diagnostic Testing
A definitive diagnosis relies on a tissue sample obtained through an incisional or excisional biopsy of the suspicious lesion. This procedure is necessary because the salmon patch can sometimes mimic other, benign lymphoid proliferations. The collected tissue undergoes pathological and immunohistochemical analysis to confirm the presence of malignant B-cells. This analysis identifies specific protein markers, such as CD20, on the cell surface, which helps classify the lymphoma subtype.
Once the diagnosis is confirmed, a systemic workup is performed to determine the extent of the disease, a process known as staging. Staging ensures that the cancer has not spread to other parts of the body, although the lymphoma is often localized to the eye. This workup typically involves comprehensive imaging, including computed tomography (CT) or magnetic resonance imaging (MRI) of the orbits. Further staging commonly includes CT scans of the chest, abdomen, and pelvis, and often a positron emission tomography (PET) scan to identify distant sites of disease. A bone marrow biopsy may also be required to assess for systemic involvement, particularly if high-risk features are present.
Primary Treatment Approaches
The management strategy for conjunctival lymphoma depends on the lymphoma subtype and the stage of the disease. For low-grade MALT lymphomas that are small and strictly localized, a watchful waiting approach may occasionally be adopted, particularly in older patients or those with other health concerns. However, the most established and effective treatment for localized disease is external beam radiation therapy (EBRT).
Radiation therapy is considered the standard approach, offering high rates of local control and complete remission, often exceeding 90% for MALT-type tumors. The treatment involves delivering a moderate dose of radiation, typically 30 to 36 Gy, over several weeks. The lens of the eye is carefully shielded to minimize long-term complications like cataract formation. Surgical excision is sometimes performed as part of the initial diagnostic procedure, and for very small, accessible lesions, it can occasionally be curative, though radiation is generally more reliable for long-term control.
For cases of lymphoma that have spread beyond the eye or involve higher-grade subtypes, systemic therapies become necessary. This includes chemotherapy or immunotherapy drugs, such as Rituximab, which targets the CD20 protein found on the surface of the malignant B-cells. In some instances where an infectious trigger is suspected, such as Chlamydia psittaci, a course of systemic antibiotics like Doxycycline has been explored as a targeted therapeutic option to eliminate the underlying stimulus.