Introduction Histological subtype is an independent prognostic factor in malignant pleural mesothelioma (MPM). Accurate typing is required to offer appropriate therapy, with surgery generally being reserved for epithelioid disease due to the poor survival in biphasic and sarcomatoid MPM. Preoperative tissue can be obtained by a variety of methods which may yield suboptimal specimens.
We aimed to investigate whether the mode of biopsy influenced the accuracy of diagnosis.
Methods We reviewed clinicopathological data from all patients who underwent radical surgery for MPM from 2000–2014, and compared subtyping from biopsies and resection specimens. In addition, a subspecialty expert consultant histopathologist reviewed biopsies from all biphasic cases.
Results In total, 335 patients had available pathological data available.
61(18.2%) showed discordance in subtyping between the diagnostic biopsy and the resection specimen. In 53 patients a poorer prognosis cell type was identified at resection (see Table).
There was poorer survival in the discordant group; median survival 8.2 vs 15.2 month (p = 0.001 HR=1.659 95% CI 1.227–2.243).
Discordance was found to be an independent predictor of survival on multivariate analysis (HR 1.653 95% CI 1.207–2.264 p = 0.002).
There was no effect of method of pre-operative biopsy on concordance (p = 0.306). There was also no difference in the accuracy of the diagnosis if a surgical biopsy was performed versus medical thoracoscopy or a radiologically guided biopsy (p = 0.768).
In 26 (18.4%) cases there was discordance between pre-operative biopsy and post-operative histological subtype. In 22 patients a poorer prognosis cell type was identified.
Conclusion These data demonstrate potential inaccuracy of current biopsy practice with accompanying impaired patient outcome. This correlates with our existing knowledge of the heterogeneity of MPM and the difficulty of subtyping from small biopsies. A wide distribution of biopsy sites within the hemithorax is likely to be more significant in obtaining an accurate histological diagnosis than the mode of biopsy itself.