Ultimately the diagnosis of cancer depends on examining a small bit of tissue to see if it has the characteristic patterns and cell types defined as cancer. The definitive way to diagnose a suspicious area is to perform a biopsy . Sometimes this is done even before doing other tests.
    This microscopic examination is carried out by a pathologist who is expert in the 
very exact criteria that separate malignant cells from normal or benign ones. It is 
essential to obtain a specimen of tissue to do this examination. The biopsy 
is the procedure for obtaining the tissue 
( see Figure: Types of Biopsy for Cancer Diagnosis ).

There are two types: 
• an incisional biopsy involves cutting 
  into a portion of the tumor , then
  stitching the area closed;
• an excisional biopsy involves 
  removing the entire tumor.