Diagnostic procedures of pleural malignant mesothelioma: our experience

The morphology of the epithelioid malignant mesothelioma (MM) of the pleura is similar to lung adenocarcinoma involving pleura. The aim of this study was to evaluate the value of immunohistochemistry in the accurate diagnosis of MM, especially of the epithelioid type with needle biopsy of the pleura.

The diagnosis of MM was established with pleural needle biopsy and tumor immunophenotyping in 30 patients. A broad spectrum of monoclonal antibodies was applied: HBME-1, E-cadherin, calretinin, cytokeratin 5/6, vimentin, thyroid transcription factor (TTF-1) and surfactant apoprotein A (SP-A).

We diagnosed 24 epithelioid, 2 biphasic and 4 sarcomatoid MM. HMBE-1 was the most sensitive tumor marker of the epithelioid type, being positive in 100% of the cases. Calretinin, E-cadherin and cytokeratin 5/6 were positive in 70%, 73%, and 50% of all tumors, respectively. TTF-1 and SP-A were negative in all MM. Vimentin was positive in spindle cells of all sarcomatoid and biphasic MM (20%).

The accurate diagnosis of MM is mandatory for appropriate treatment decision (surgical or nonsurgical). Our results demonstrate that HMBE-1 is a most useful diagnostic antibody for epithelioid MM, and TTF-1 for lung adenocarcinoma (its thyroid origin excluded) involving pleura.