HUMAN BIOLOGY

Genes and disease: CanCer 433

hoW is cancer diagnosed?

• Preliminary procedures for diagnosing cancer include blood
  tests for substances produced by cancer cells and various
  types of medical imaging.


• Only a biopsy can definitely diagnose cancer.


• Everyone should be aware of the seven common cancer
  warning signs.

taKe-Home messaGe

Biopsy is the surest way to diagnose cancer

When a test or exam suggests that a patient has cancer, the

usual next step to confirm the diagnosis is biopsy. A small

piece of suspect tissue is removed from the body through

a hollow needle or exploratory surgery. A pathologist then

microscopically examines cells of the tissue sample to see if

cancer cells are present (Figure 22.13).

Table 22.4 lists the American

Cancer Society’s seven common

cancer warning signs. Notice that

the first letters of the signs spell

CAUTION. Watching for these

signs can help people spot cancer

in its early stages, when treat-

ment is most effective. Anyone who has one or more of these

signs should be evaluated by a doctor as soon as possible.

Today sophisticated tools of personal genetic profil-

ing may be used to identify an inherited predisposi-

tion for some forms of cancer. Prime examples are the

mutated forms of BRCA1 and BRCA2 associated with

familial breast cancer. The genes are located on different

Figure 22.12 Radioactive tracers also can reveal cancer

tumors. Shown above are scans of the thyroid gland from

three patients who have ingested radioactive iodine, which

is taken up by the thyroid. (© Cengage Learning/Gary Head)

normal thyroid

cancerous

enlarged

Figure 22.13 This light microscope image shows cancerous cells in

breast tissue. The cancer cells are stained brown. Normal cells are the

ones with lighter staining. (From the archives of http://www.breastpath.com, courtesy Askew,

Jr., M.D., P.A. Reprinted with permission, 2004 Breastpath.com)

normal

cells

cancerous

cells

*Notice that the first letters of the signs spell the word CAUTION.

Source: Based on American Cancer Society.

Change in bowel or bladder habits and function

A sore that does not heal

Unusual bleeding or bloody discharge

Thickening or lump

Indigestion or difficulty swallowing

Obvious change in a wart or mole

Nagging cough or hoarseness

Table 22.4 The Seven Warning Signs of Cancer*

Figure 22.14 Animated! Personal genetic

profiling helps identify women at risk of

inherited breast cancer. Faulty BRCA1 and

BRCA2 genes underlie the majority of cases

of familial breast cancer. (© Cengage Learning)

13

BRCA2

17

BRCA1

biopsy Microscopic
examination of tissue for
evidence of cancer cells;
biopsy is the definitive test
for cancer.

chromosomes (Figure 22.14), and a female who inherits

one or both of them has a dramatically increased risk of

developing breast cancer.

Copyright 2016 Cengage Learning. All Rights Reserved. May not be copied, scanned, or duplicated, in whole or in part. Due to electronic rights, some third party content may be suppressed from the eBook and/or eChapter(s).