Pseudomesotheliomatous Adenocarcinoma

Pseudomesotheliomatous adenocarcinoma is a lung cancer (usually adenocarcinoma) that spreads along the pleura and encases the lung the way mesothelioma does. On imaging, and sometimes under the microscope, it can be mistaken for mesothelioma.

Origin

The term was introduced in 1976 to describe lung carcinomas that grew in a diffuse, rind-like pattern over the pleura and had been misdiagnosed as mesothelioma at the time.

Significance in Asbestos Context

Telling the two apart matters for treatment and for a claim. Immunohistochemistry usually settles it: lung adenocarcinoma stains for markers such as TTF-1, napsin A and claudin-4, while mesothelioma stains for calretinin, WT1 and D2-40. A misread in either direction affects how a case is valued, because trusts and juries treat mesothelioma and lung cancer very differently. Asbestos also causes lung cancer, so a corrected diagnosis does not necessarily end a claim, but the evidence needed changes: lung cancer claims generally require proof of asbestosis or pleural disease and a longer exposure history.

Example Sentence

The tumor encased the whole left lung like a mesothelioma, but the immunostains were positive for TTF-1 and napsin A, and the final diagnosis was pseudomesotheliomatous adenocarcinoma of the lung.

Related Terms

Lung Adenocarcinoma, Mesothelioma, Immunohistochemistry, Thyroid Transcription Factor-1 (TTF-1), Calretinin, Differential Diagnosis, Mesothelioma Misclassification

Notes

• If your diagnosis was changed between mesothelioma and lung cancer, ask for the complete pathology, including every immunostain.
• Keep the tissue blocks; an independent pathology review may be needed.
• Tell your lawyer about any change in diagnosis right away.