Biopsy, Not Flow Cytometry, Is Best for Diagnosing Orbital Lymphoma

Flow cytometry is insufficient for firm diagnosis of low grade B-cell lymphoma, researchers found in a report presented at the American Society of Ophthalmic Plastic and Reconstructive Surgery 52^nd Annual Fall Scientific Symposium in New Orleans, November 11-12.

Approximately a fourth of malignant orbital tumors in adults at least 60 years of age are orbital lymphoma. The most common type is low grade B-cell lymphoma, whose most common subtype is extranodal marginal-zone B-cell lymphoma (EMZL). Diagnosing which type of orbital lymphoma a patient has is typically conducted through imaging studies, biopsy of fresh frozen tissue samples, or tissue flow cytometry. However, flow cytometry may not be the optimal use of sample tissue, the researchers said. The objective of the study was to determine how flow cytometry helps diagnose orbital lymphoma.

The researchers retrospectively reviewed 453 medical charts from 2010 to 2020 involving orbital lesions, based on current procedural terminology (CPT) codes, who underwent flow cytometry. The investigators identified 22 patients (64% women) who had been diagnosed with orbital lymphoma and included them in the study. 

They found that most patients had B-cell lymphoma, and about half (n=11) of those patients had the EMZL subtype. The next most common presented subtypes were follicular lymphoma (14%) and atypical (14%), followed by Extranodal NK/T-cell (9%) and unspecified B-cell (5%). Diffuse large B-cell lymphoma (DLBCL) and Burkitt each accounted for 4%. Two patients with B-cell acute lymphoblastic leukemia underwent flow cytometry. Both biopsy samples indicated immunophenotypic results that matched final diagnosis.

Flow cytometry of fresh frozen biopsy tissue had positive results 55% of the time. In the majority of those cases (81%), no cluster of differentiation (CD) marker was identified. The 6 patients who had extranodal NK/T-cell, unspecified B-cell, or atypical lymphoma did not have any positive flow.

The researchers concluded that biopsy is optimal to rule out other diseases the immunophenotypic pattern indicates.

“Testing for specific markers may only be useful diagnostically when other tests remain inconclusive or in distinguishing lymphoma from other disease processes that may present similarly such as other benign lymphoproliferative disorders,” the investigators said. “Overall, flow cytometry may be most useful as a fast and sensitive diagnostic method in cases where biopsy is not an option, but overall is not sufficient for establishing a firm diagnosis alone. When tissue is limited, we recommend using it for permanent stains rather than cytology.”

Reference

Mitchell MK, Nasrazadani DA, Timoney PJ et al. Is flow cytometry worth the time, money, and tissue? A diagnostic approach to orbital lymphoma: The role of flow cytometry. Poster presented at ASOPRS 52nd Annual Fall Scientific Symposium; November 11-12, 2021; New Orleans, LA.