Correlation between cytology Oil Red O staining and lung biopsy specimens: utility of the lipid-laden macrophage index.

Introduction: Oil Red O staining is used for enumeration of the lipid-laden macrophage index (LLMI) as a surrogate for aspiration. As part of quality improvement efforts aimed at optimizing resource utilization, the utility of this stain in current cytopathology practice was re-evaluated. The objective of this study was to explore the clinical utility of Oil Red O staining in bronchoalveolar lavage (BAL) samples by correlating the LLMI with findings in concurrent histologic tissue samples.

Materials And Methods: Lung transbronchial biopsy specimens that suggested aspiration that were submitted with concurrent BAL cytology samples were retrieved. Lung tissue biopsies were reviewed for the presence of foamy alveolar macrophages (graded as 0, 1+, and 2+), foreign material, and giant cells. The concurrent BAL was reviewed with consensus determination of the LLMI.

Results: A total of 53 cases were identified. On histology, 13 cases (24.5%) were found to have no foamy alveolar macrophages, 23 cases (43.4%) were found to have 1+ foamy alveolar macrophages, and 17 cases (32.1%) were found to have 2+ foamy alveolar macrophages. Six cases (11.3%) were found to have foreign material, and 10 cases (18.9%) were found to have multinucleated giant cells. The average LLMI score was 16, with 44 (83.0%) in the low range (LLMI <40) and 9 (17.0%) in the intermediate range (LLMI of 40-90).

Conclusions: None of the cases in our study had an LLMI that exceeded the cutoff value for which aspiration would be suspected. We found no correlation of the LLMI with lung biopsies that suggested aspiration.