3. Which histologic type of malignant mesothelioma is shown in this photomicrograph?
4. Which histologic type of malignant mesothelioma is shown in this photomicrograph?
5. A 65-year-old man presents with persistent chest pain and unexplained weight loss. On initial examination, he is found to have a hemorrhagic pleural effusion, which is evacuated. A CT scan reveals irregular pleural thickening. A biopsy of the pleural lesions demonstrates the histopathologic features shown in this photomicrograph. The tumor has diffuse expression of pan-cytokeratin. Which of the following markers, if positive, would support a diagnosis of mesothelioma and rule out adenocarcinoma?
A. Cytokeratin 7
B. Cytokeratin 20
E. None of the above
6. A pleural tumor composed of tubular and papillary structures raises the differential diagnosis between epithelioid mesothelioma and adenocarcinoma. Which of the following immunostains would be positive if the tumor were a mesothelioma?