A review of over 2,000 cases of mesothelioma in WA since 1962 has shown a cytological diagnosis of the disease subtype is sufficient.

But histological confirmation, which adds delays, is costly and more invasive, remains important in research settings and for establishing potential new treatments, the limbic was told.

Associate Professor Fraser Brims, from the Sir Charles Gairdner Hospital and Curtin University, said the study showed – for the first time – that a cytological diagnosis of epithelioid mesothelioma does not lead to an underdiagnosis of the biphasic subtype.

“For most cases, a cytology tap is sufficient to diagnose epithelioid mesothelioma and patients don’t need further testing,” he said.

“This is a big step forward. Clinicians do not need to go after a histological diagnosis if it is shown to be epithelioid mesothelioma on cytology.”

The study found 1,212 cases (60%) were identified as epithelioid mesothelioma. 499 (41%) were diagnosed solely by fluid cytology.

There was no difference in survival between the patients diagnosed as epithelioid subtype by either cytology or histology, suggesting cytology was not missing other subtypes that typically had poorer outcomes.

Associate Professor Brims said a previous audit of practice had shown cytology reports were available about 29 days before histology reports.

“It’s important from a medicolegal point of view as the vast majority of cases are due to occupational injury and patients are entitled to compensation. If they are diagnosed early, then they have more time to pursue that.”

He said the legal system in WA was not interested in the subtype of mesothelioma.

The study showed median survival had increased over time from 7.6 months in the 1970s to 11.8 months. However the data reflected earlier diagnosis rather than improvements in treatment options, Associate Professor Brims said.

Immunohistochemical techniques on highly cellular fluid samples had become increasingly available over the last 20 years to support cell morphology.