Flow cytometry in reactive lymph node aspirates: Evaluation of distribution of populations with immunophenotypic
Priyanka Goel1, Seema Acharya1, Sana Ahuja1
1Department of Pathology, Shri Guru Ram Rai Institute of Medical and Health Sciences, Dehradun, India.
Insights
Flow cytometry (FCM) aids lymphoma diagnosis by identifying cell outliers. Benign lymph nodes can show these outliers, but light chain restriction absence confirms a non-lymphoma diagnosis, preventing misdiagnosis.
Area of Science:
- Hematopathology
- Immunophenotyping
- Diagnostic Cytology
Background:
- Fine needle aspiration cytology (FNAC) combined with flow cytometry (FCM) improves lymphoma diagnostic accuracy.
- Differentiating reactive lymph nodes from low-grade lymphomas using FNAC is challenging for cytopathologists.
- Immunophenotypic outliers, detected by FCM, can be present in both benign and malignant lymphoid populations.
Purpose of the Study:
- To evaluate the distribution of lymphoid populations and the presence of immunophenotypic outliers in benign lymph node aspirates using FCM.
- To determine if benign lymph node aspirates can mimic lymphoma findings through FCM analysis.
- To assess the utility of multiparameter FCM in conjunction with clinical correlation for accurate lymphoma diagnosis.
Main Methods:
- FCM analysis was performed on FNAC/scrape material from 30 benign lymph node cases.
- Lymphoid populations were analyzed for distribution and presence of immunophenotypic outliers.
- Key markers including CD5, CD19, CD10, CD7, and light chains were assessed.
Main Results:
- T-cell predominance was observed in most cervical lymph node samples.
- B-cell events showed CD5/CD19 co-expression (23.94±9.51%) and CD10/CD19 co-expression (3.2%-20.2%).
- Loss of CD7 expression was noted in 17 cases (2%-28.4%) and CD5 in 1 case (12.7%) of T-cell events; none showed light chain restriction.
Conclusions:
- Immunophenotypic outliers suggestive of lymphoma can be present in benign lymph node aspirates.
- Absence of light chain restriction and normal CD4:CD8 ratios are key indicators of benignity.
- Multiparameter FCM combined with clinicoradiological correlation is crucial to prevent lymphoma overdiagnosis.
Background:
Diagnostic accuracy of fine needle aspiration cytology for lymphomas has markedly improved when used in conjunction with flow cytometry (FCM), especially to differentiate reactive lymph node aspirates from low-grade lymphomas, a challenge for cytopathologists. Lymphoma diagnosis by FCM depends on detection of immunophenotypic B- and T-cell outliers, also present in benign lymph nodes albeit in subsets of cells. These can mimic heterogenous populations obtained from lymphomas partially involving lymph nodes.
Methods:
In the present study, FCM of fine needle aspiration/scrape material from 30 cases of benign lymph nodes was evaluated for the distribution of lymphoid populations and the presence and percentages of immunophenotypic outliers.
Results:
The majority of the samples were cervical nodes with all cases showing T-cell predominance. CD5/CD19 co-expression was seen in 23.94 ± 9.51% (20 cases) and CD10/CD19 co-expression in 3.2%-20.2% (8 cases) of B-cell events. None of these cases showed light chain restriction. Loss of CD7 (2%-28.4%) and CD5 (12.7%) expression was seen in 17 cases and 1 case, respectively, of T-cell events.
Conclusion:
Immunophenotypic outliers suggestive of lymphomas could be seen in non-lymphomatous lymph node aspirates in a subset of the cell population. However, they could be defined as benign due to absence of light chain restriction and normal CD4:CD8 ratios in all but one case, which was confirmed to be benign after clinical correlation and excisional biopsy. Thus, multiparameter FCM along with clinicoradiological correlation can prevent overdiagnosis of lymphomas.
