Exclusive intrapulmonary lepidic growth of a malignant pleural mesothelioma presenting with pneumothorax and involving the peritoneum.

We report a rare case of malignant pleural mesothelioma presenting clinically with pneumothorax and histologically with an exclusive intrapulmonary lepidic growth. Neither intrathoracic nodules nor pleural thickening were found. The patient subsequently experienced acute abdominal pain with peritonitis and intestinal occlusion by peritoneal mesothelioma. The morphologic clues leading to the correct diagnosis of mesothelioma with prominent intrapulmonary growth are briefly discussed.