arising from the follicular cells and tends to grow
slowly. This form of thyroid cancer is more com-
mon in people who have had previous RADIATION
THERAPYto the neck, lower face, or upper chest,
and in people who have autoimmune
(Hashimoto’s) THYROIDITIS. When papillary thyroid
cancer metastasizes, it does so through the lym-
phatic system and usually only to adjacent lymph
nodes.
Follicular thyroid cancer About 15 percent of
thyroid cancers are follicular carcinomas, which
also develop in the follicular cells. Follicular carci-
noma does not correlate to previous radiation
therapy or benign thyroid conditions. This form of
thyroid cancer tends to metastasize through the
BLOOD circulation, causing secondary tumors
remote from the original tumor. With early detec-
tion and treatment (before METASTASIS), follicular
thyroid cancer is highly curable. After metastasis,
however, the prognosis declines considerably.
Medullary thyroid cancer About 8 percent of
thyroid cancers are medullary carcinomas, which
develop in the parafollicular cells which synthe-
size CALCITONIN. Consequently, excessive blood lev-
els of calcitonin in the absence of other health
conditions strongly suggest this thyroid cancer.
Because these cells are less organized structurally,
cancer that arises from them is less clearly delin-
eated and accordingly more difficult to see or feel.
This form of thyroid cancer often occurs in the
inherited genetic disorder MULTIPLE ENDOCRINE NEO-
PLASIA(MEN). Rarely, medullary thyroid cancer is
inherited without MEN. Medullary thyroid cancer
tends to metastasize early to adjacent lymph
nodes. Distant metastasis to remote sites signifi-
cantly worsens the prognosis.
Anaplastic thyroid cancer About 2 percent of
people who develop thyroid cancer have anaplastic
carcinoma, which is the most lethal of the cancers
that involve the thyroid gland. It grows rapidly and
spreads aggressively. Anaplastic thyroid cancer is
more likely to develop in men over the age of 70
and is very rare in people under age 50.
Symptoms and Diagnostic Path
The typical symptom of any form of thyroid can-
cer is a painless lump or swelling in the neck. The
person may see the swelling in the mirror or feel
the lump. Many times a doctor discovers a thyroid
cancer during a routine medical examination or
when examining the neck for other reasons. Some
people experience difficulty swallowing or talking,
depending on the location and size of the tumor.
The diagnostic path typically includes blood
tests to measure the levels of the thyroid hor-
mones, including THYROID-STIMULATING HORMONE
(TSH), though the results may be normal. ULTRA-
SOUNDand a radioisotope iodine reuptake test can
identify the tumor and provide some clues as to
whether it is cancerous, though fine-needle aspi-
ration (FNA) biopsy provides the definitive diag-
nosis. In FNA the endocrinologist uses a small
needle and syringe to withdraw a sample of cells
from the growth. Laboratory examination then
determines whether the cells are cancerous, and
what type of cancer is present.Treatment Options and Outlook
For nearly all thyroid cancers, treatment is surgery
to remove the thyroid gland (thyroidectomy) fol-
lowed by radioactive iodine to kill any remaining
thyroid cells. The radioactive iodine acts as a form
of CHEMOTHERAPYand invades thyroid cells no mat-
ter where they are in the body. The exception is
for medullary thyroid cancer, which arises from
the parafollicular cells that do not take in iodine.
The doctor may choose conventional chemother-
apy or radiation therapy to follow surgery for
medullary thyroid cancer. When a papillary thy-
roid cancer is small and contained, the doctor may
feel lobectomy (removal of the involved lobe of
the thyroid gland) is adequate. The decision must
consider numerous factors, however, and the per-
son who has thyroid cancer should make an
informed choice based on full consideration of
those factors.
Thyroid cancers detected and removed early in
their development have the highest treatment
success rate, and can be up to 90 percent curable
(papillary and follicular). Medullary and anaplastic
thyroid cancers are more difficult to diagnose in
their early stages, and thus tend to be more
advanced and often have metastasized by the time
treatment begins. After thyroidectomy, it is neces-
sary to take lifelong thyroid hormone supple-
ments.thyroid cancer 161