Chapter 21: Lung Cancer
Peripherally located vs. centrally located
1. Centrally located (mainstem bronchus):
Have the highest association with smoking. Include squamous cell carcinoma and small cell
carcinoma. These are generally centrally located, hence mainstem bronchus types of
locations. Squamous cell are more common than small cell carcinomas.
2. Peripherally located:
Adenocarcinomas (the more common primary lung cancer, more common than squamous)
are more peripheral than central. Shifted to the periphery b/c of the filters of the cigarettes.
The filters prevented the large carcinogens from passing in, but the small carcinogens still
passed through, and they are not trapped in the main stem, but trapped in the periphery.
There are at least 3 or 4 types of adenocarcinoma. One obviously does have a smoking
relationship, while the others do not. The ones that do not have a smoking relationship
include bronchiolar alveolar carcinoma, and large cell adenocarcinoma of the lung (scar
Cytology: know what squamous cancer looks like with a pap smear. A lot of people think that the
Papanicolaou stain is only done for cervical carcinoma. This is not the case. This is a famous stain
(pap smear) used for all cytological specimens on for all organs. The stain stain’s keratin bright
red. Slide: (pic) pt that is a smoker with a centrally located mass. Showing sputum sample with a
Papanicolaou (pap smear) stain – has red keratin, which is squamous cell carcinoma. If this were a
cervical pap smear from a woman that is 40 years of age, this is squamous cell carcinoma. The
keratin is staining bright red! (bright red cytoplasm = keratin = squamous cell carcinoma).
Papanicolaou stains keratin bright red.
Example: small cells that look like lymphocytes – this is small cell carcinoma. This is more difficult to
dx, b/c sometimes diff to tell the difference from lymphocytes. Slide shows malignant cells. Small
cell carcinoma is the most malignant cancer of the lung. Rx? Radiation and chemo (not