Clonal Bronchopulmonary B-Cell Proliferations of Indeterminate Malignant Potential in Patients with Common Variable Immune Deficiency (CVID) associated Granulomatous Lymphocytic Interstitial Lung Disease (GLILD)

Abstract Introduction/Objective Pulmonary extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue (MALT) is often challenging to distinguish from reactive nodular lymphoid hyperplasia, and assessing B-cell clonality in such cases is crucial in making the distinction. However, patients with common variable immune deficiency (CVID) can harbor clonal or oligoclonal lymphoid populations in their tissues, particularly in association with granulomatous lymphocytic interstitial lung disease (GLILD), making the distinction from MALT lymphoma extremely challenging. We report six cases of GLILD with clonal or oligoclonal B cell infiltrates in lung wedge resection specimens and describe their clinicopathologic characteristics, management, and outcomes. Methods/Case Report A retrospective review was performed to collect lung wedge resection specimens from patients with CVID showing atypical B-cell infiltrates associated with GLILD between 01/2015 and 08/2023. The clinicopathologic findings, management, and response to treatment were studied. Results (if a Case Study enter NA) A total of six GLILD cases were identified with variable degrees of architectural and cytologic lymphoid atypia. Clonality of the lymphoid infiltrate was assessed by kappa/lambda in situ hybridization staining in all six, flow cytometry in 3/6, and IGH gene rearrangement in 4/6 cases. The infiltrate showed frank lambda restriction in 1/6, lambda predominance in 1/6, polytypic expression in 1/6, and no significant plasmacytic component in 3/6 cases. Flow cytometry detected atypical light chain skewed B-cell populations in 3/3 of cases. IGH was positive for clonality in 3/4 and oligoclonal in 1/4 cases. Four patients received therapeutic intervention for GLILD, including one with Rituximab monotherapy, two with Rituximab+Azathioprine, and one with Rituximab+Mycophenolate leading to marked symptomatic and radiologic improvement in all four patients. The remaining two patients were observed to have stable disease. Conclusion Patients with CVID can harbor clonal B-cell populations due to their underlying immune dysfunction. Studies have shown that these can be transient and may not always progress to overt lymphoma. In the setting of GLILD, detecting these populations makes the distinction from MALT lymphoma very challenging. Given that the first- line therapy for both GLILD and MALT is anti-CD20 therapy, the malignant potential of these clones remains uncertain and can only be determined with long-term clinical follow-up.