Microvascular density using the Chalkley method: a potential alternative to the World Health Organization nuclear grading in pleural mesothelioma prognostication

To the Editor,
Pleural mesothelioma is a malignancy of the thoracic serosa. Outcomes are typically poor, but prognostication is challenging. Applied prognostic factors include age, gender and histological subtype, with epithelioid and biphasic mesothelioma having better outcomes than sarcomatoid mesothelioma.1,2 The World Health Organization (WHO) currently recommends the use of a two-tier grading system that is only applicable to epithelioid mesothelioma, which in some studies shows moderate agreement and reproducibility.3,4 Blood flow is essential for tumour growth and high microvascular density (MVD) is an adverse prognostic factor for pleural mesothelioma.5,6 We aimed to determine the suitability of MVD assessed by the Chalkley method for prognostication in all histological subtypes of mesothelioma and compared this with the WHO two-tier grading system for epithelioid mesothelioma.