Major treatment decisions are made on the basis of whether a tumor is classified as a small cell lung carcinoma (SCLC) or as one of the non-small cell lung cancer (NSCLC) varieties (squamous, adenocarcinoma, large cell carcinoma, bronchioloalveolar carcinoma, and mixed versions of these). The histologic distinctions between SCLC and NSCLC include the following: SCLC has scant cytoplasm, small hyperchromatic nuclei with fine chromatin pattern and indistinct nucleoli with diffuse sheets of cells, while NSCLC has abundant cytoplasm, pleomorphic nuclei with coarse chromatin pattern, prominent nucleoli, and glandular or squamous architecture. . | Chapter 085. Neoplasms of the Lung Part 2 Major treatment decisions are made on the basis of whether a tumor is classified as a small cell lung carcinoma SCLC or as one of the non-small cell lung cancer NSCLC varieties squamous adenocarcinoma large cell carcinoma bronchioloalveolar carcinoma and mixed versions of these . The histologic distinctions between SCLC and NSCLC include the following SCLC has scant cytoplasm small hyperchromatic nuclei with fine chromatin pattern and indistinct nucleoli with diffuse sheets of cells while NSCLC has abundant cytoplasm pleomorphic nuclei with coarse chromatin pattern prominent nucleoli and glandular or squamous architecture. Among the molecular distinctions SCLC displays neuroendocrine properties absent in NSCLCs production of specific peptide hormones such as adrenocorticotropic hormone ACTH arginine vasopressin AVP atrial natriuretic factor ANF gastrin-releasing peptide GRP and differences in oncogene and tumor-suppressor gene changes SCLCs have RB mutations in 90 and p16 abnormalities in 10 but never have KRAS or EGFR mutations while NSCLCs have RB mutations in only 20 p16 changes in 50 KRAS mutations in 30 and EGFR mutations in 10 . Both types have frequent p53 mutations 70 in SCLC and 50 in NSCLC 3p allele loss 90 in both telomerase expression 90 in both and tumor-acquired promoter methylation in multiple genes 80 in both often involving the same genes including RASSF1A SCLCs are initially very responsive to combination chemotherapy 70 responses with 30 complete responses and to radiotherapy 90 responses however most SCLCs ultimately relapse. By contrast NSCLCs have objective tumor shrinkage following radiotherapy in 3050 of cases and response to combination chemotherapy in 20-35 of cases. At presentation SCLCs usually have already spread such that surgery is unlikely to be curative and given their responsiveness to chemotherapy are managed primarily by chemotherapy with or without radiotherapy. Chemotherapy clearly .
