Effective chemotherapy is available for many types of lung tumors; however, to select the most appropriate regimen, precise classification is essential. The most important differentiation is that between small cell and non-small cell anaplastic carcinoma. It is also important to distinguish mediastinal neoplasms and neoplasms metastatic to lung from primary lung tumors. Processing tissue in methacrylate and epoxy resins results in excellent preservation of histologic detail and allows for maximum resolution under the light microscope. In addition, histochemical and immunochemical procedures can be carried out in these preparations, allowing the pathologist to more precisely classify the various tumors.