Lung cancer. Light micrograph of a section through a lung with bronchoalveolar cell carcinoma. Bronchoalveolar is a subtype of Adenocarcinoma. A malignant (cancerous) tumour (dark mass) is at centre left. This carcinoma originates in the cells that line the walls of the alveoli (air sacs, white spaces). Symptoms include chest pain, shortness of breath and a cough. Treatment is with surgical removal of the tumour where possible and chemotherapy or radiotherapy.