Localized pleural malignant mesothelioma. Report of two cases simulating pulmonary carcinoma and review of the literature

Aims: To describe two cases of localized malignant mesothelioma with a predominantly intrapulmonary growth which led to a pre-operative diagnosis of pulmonary carcinoma. Materials and Methods: Both cases presented as intrapulmonary masses, while at CT scan the pleura appeared not significantly thickened. In one patient the main bronchus was diffusely infiltrated by the tumour. In both cases, a preoperative biopsy showed a proliferation of large cells leading to a diagnosis of non small cell lung carcinoma. Histologic examination of the surgical specimens revealed features consistent with epithelioid mesothelioma with deciduoid features in one case and with biphasic mesothelioma in the other. Both cases were diffusely positive with anti-calretinin antibody, while anti-TTF1, anti-surfactant and anti-CEA antisera were negative. Conclusions: Localized malignant mesotheliomas are unusual and predominantly intrapulmonary growth is rare. Pathologists should be aware of this possibility to avoid misdiagnosis, particularly in small biopsies.