Clinical Oncology

Chapter 3

Head and Neck Cancer

General Oncology in Head and Neck Cancers

1. What is field cancerization? Who discovered it?

•The concept of “field cancerization” was first introduced by Slaughter et al in 1953.••It was conceptualized after the observation that the mucosa beyond the boundaries of the tumor possesses some histologic changes.••The classic view of the term “field cancerization” hypothesized that large areas of head and neck mucosa are affected by carcinogen exposure, resulting in a wide field of premalignant disease that gives rise to multiple independent primary tumors.••Field cancerization is also called a field defect or field effect.

2. What are the theories of field cancerization?

Theories of field cancerization:

•One theory states that multiple squamous cell lesions occur independently of each other. This is due to the exposure of the oral cavity to carcinogens in at the same time leading to multiple genetic abnormalities in the entire area (polyclonal theory).

•An alternative theory states that multiple lesions arise due to the migration of dysplastic and altered cells with two different patterns (monoclonal theory):

•–Migration of malignant cells through the saliva (micrometastasis).

•–Intraepithelial migration of the progeny of initially transformed malign-ant cells.

3. What are the steps in field cancerization?

Field cancerization model:

•The process of carcinogenesis begins with a stem cell which develops one or more genetic and epigenetic alterations.

•It includes three main steps:

–The first phase (patch formation): conversion of a single stem cell (patch) into a group of cells (clone) which carry the genetic alterations without a proper growth control pattern.

•–The second phase (clonal expansion).

•–The third phase (transition to the tumor).

4. What is the definition of synchronous SPM (second primary malignancy)?

•A synchronous SPM is diagnosed simultaneously or within 6 months of the index tumor.

•It is the second leading cause of death in HNSCC.

•It may be synchronous or metachronous.

5. What is metachronous second primary cancer (SPM)?

Metachronous SPM is diagnosed more than 6 months after the index tumor.

6. What is the criteria to define an SPM?

The original criteria as defined by Warren and Gates include:

•Histologic confirmation of malignancy in both the index and secondary tumors.

•The two malignancies must be anatomically separated by normal mucosa.

•The possibility of the SPM being a metastasis from the index tumor must be excluded.The criteria were modified by Hong et al. It includes:

•If both tumors originate from the same subset, then the second tumor must be separated from the first by at least 2 cm of normal epithelium or had to occur after an interval of at least 3 years.