Pleural Resections for Malignant Mesotheliomas
The diagnosis of malignant mesothelioma is usu-ally established on the basis of cytologic material or small incisional biopsies. Rarely, malignant mesotheliomas are resected in an attempt to obtain a surgical cure. For tumors arising in the chest, these specimens generally consist of lung with en bloc removal of any adjacent involved mesothelium-lined structures such as the parietal pleura of the chest wall, the pericardium, and the diaphragm. These specimens can generally be handled using the same principles guiding the dis-section of other lung specimens, as detailed above. When it comes to malignant mesotheliomas, how-ever, a few points warrant special emphasis.
1. Immunohistochemistry and electron mi-croscopy have become important adjuncts to routine microscopic evaluation in the diagnosis and classification of malignant mesothelioma. For lung specimens with pleura-based tumors, always consider the possibility of a malignant mesothelioma, and process a small portion of the tumor for electron microscopy should this mod-ality be needed to establish the diagnosis.
2. Because of the variable and sometimes deceptively bland histopathologic appearance of maligant mesotheliomas, the diagnosis and classification are aided by ample sectioning for histologic evaluation. Suspected malignant meso-theliomas should be sampled much more exten-sively than the conventional lung carcinoma. For smaller lesions, submit the tumor in its entirety. For large lesions, submit at least one section per centimeter of tumor.
3. Depending on the extent of tumor involve-ment along mesothelium-lined surfaces, these resections may be anatomically complex. Do not rush through the dissection.
Instead, take the time necessary to orient the specimen, identify all structures present, document the extent of tumor spread, and locate each margin (e.g., bronchus, pulmonary vessels, chest wall, diaphragm) for histologic evaluation.
4. Submit additional sections of uninvolved lung, and evaluate them for the presence of ferru-ginous bodies, pleural plaques, and interstitial fibrosis.
· What procedure was performed, and what structures/organs are present?
· Is a neoplasm present?
· How large is the tumor, and where is it located?
· What are the histologic type and grade of the tumor?
· Does the tumor infiltrate the large airways, pleura, or vessels?
· What is the status of each of the margins (paren-chymal, vascular, and bronchial)?
· Does the tumor involve the lobar or main-stem bronchi?
· Is there any evidence of metastatic disease? Record the number of lymph nodes examined and the number of lymph node metastases. If nodal involvement is only by direct extension, this feature should be noted.
· Is there any pathology in the non-neoplastic lung (e.g., granulomas, postobstructive pneu-monia)?