Histological grading of therapy induced regression in squamous cell carcinomas of the oral cavity. A morphological and immunohistochemical study.

Squamous cell carcinomas in the oral cavity and the oropharynx were diagnosed in 84 patients. After verification by biopsy, 79 of these patients were treated preoperatively with mitomycin C and 5-fluro-uracil, radiated and operated 3-5 weeks later. The effectiveness of adjuvant preoperative radio-chemotherapy was evaluated histologically. Serial sections of the entire tumor specimen were investigated and the percentage of vital cancerous tissue in the total tumor area was assessed. Regression was classified into four grades. Grades I and II were regarded as good response to adjuvant preoperative radio-chemotherapy, while grades III and IV stood for bad or no response. Morphologically questionable residual tumor infiltrates could be clarified by immunohistochemical methods with antibodies against vimentin, desmin and Lu-5. The histological assessment of the regression grade of operated tumor specimens allows a clinically relevant, morphologically exact and reproducible evaluation of the effect of preoperative radiochemotherapy.