Carcinoma of the thyroid represents less than half of 1% of the over-all cancer problem as represented in incidence and mortality statistics, but it is of considerable importance to the physician for the following reasons:

1. Evaluation of an enlarged and/or nodular thyroid gland is a rather common office problem. The possibility of cancer must always be considered.

2. The relationship of nodular goiter to cancer of the thyroid gland has been the subject of great debate in medical journals during the last fifteen years. Recommendations range from removing all nodular goiters to removing none, with a variety of compromise or middle-of-the-road positions in between. It is not surprising that the physician is perplexed as to what is the proper advice to give his patient.

3. The prognosis of thyroid cancer is extremely variable depending on the particular type of lesion involved. It may produce death in a matter of weeks or months or allow the patient to live for decades, even with evidence of persisting disease. It is important for the physician to be aware of these differences.

Epidemiology

Actually there is a fair amount of variation in age, sex, and other patterns according to the specific type of thyroid cancer involved. This will be dealt with in Table 2. The data presented on p. 106 relate to the over-all grouping of thyroid cancer.

Table 2. Classification And Some Characteristics Of Thyroid Cancer*

Type

%

Age distribution

Sex ratio (F:M)

Sex

Cervical node metastases

Obstructive symptoms

Distant metastases

Prognosis

Remarks

Papillary

55.7

Youngest, 4 Oldest, 82 Peak, 20-39

71:29

Average 2-4 cm. but may be very small and occult

Frequent, often bilateral; the so-called "lateral aberrant thyroid"

Uncommon

Not common but can occur especially late, chiefly to lung; some metastases pick up I131

Generally good; course prolonged; patients may survive decades with disease

Thyroid cancer occurring in children and young adults usually of this type

May simulate benign adenoma or nodular goiter clinically

Follicular

11.3

Slightly older than patients with papillary type; 25% of patients in 2nd to 4th decades Youngest, 9 Oldest, 85

67:33

Usually occupies one lobe; 2-5 cm. or larger

Not common (±20% of patients)

Uncommon except in large tumors

Fairly common; may be presenting symptom; predominantly to bones; also to lung; metastases frequently pick up I131"

May be good; course prolonged even in presence of distant metastases

Often unsuspected clinically

May simulate benign adenoma or nodular goiter; often long history

Many synonyms: Malignant adenoma Benign metastasizing struma Angio-invasive adenoma Alveolar carcinoma Adenocarcinoma

Hurthle cell

6.4

Older ages Peak, 40-60

67:33

Usually small and encapsulated but 1/3 larger than 6 cm.

Common; associated with distant metastases

Uncommon

Fairly common, especially to lung and bone; no pick up of I131

Not as good as papillary or follicular but course also prolonged in presence of distant metastases

May simulate benign adenoma or nodular goiter clinically

In 80% of patients with Hurthle cell and follicular types, history of goiter 1 to 20 years

Solid

12.1

Older ages Peak, 40-60

62:38

Bulky; non-encapsulated ; 5-10 cm.; often fixed, bilateral

Frequent, ±50%

Common

Quite common; to bone and to lung and other viscera; no pick up of l131

Very poor; course may be short

Solid and giant cell types grouped together by some and called anaplastic

Usually occur without previously known goiter

Clinical suspicion of cancer usually present

Giant cell

8.8

Oldest age range

Peak, 40-70

61:39

Large; bulky; bilateral; 8-10 cm.

Frequent, involving neck and mediastinum

Very' common

Very common; mainly to lung and other viscera; rare to bone; no pick up of I131

Very poor, course is extremely brief

One of most rapidly fatal cancers known

Death usually due to obstructive symptoms

All diagnosed as cancer clinically

Unclassified

5.7

*Based on 705 cases. Memorial Hospital for Cancer and Allied Diseases, 1930-1954; data compiled by E. L. Frazell, F. W. Foote, and R. Oropeza.

Incidence

Men

Women

800 new cases each year

2,200 new cases each year

0.38 of male cancer incidence

0.98 of female cancer incidence

Mortality

Men

Women

400 deaths each year

700 deaths each year

0.38 of male cancer mortality

0.58 of female cancer mortality

Rates And Ratios

Male

Female

Sex ratio

Incidence per 100,000

0.9

2.4

0.4 to 1

Mortality per 100,000

0.5

0.9

0.5 to 1

Trend last ten years

Male

Female

Incidence-increase

-

17.58

Mortality

-

-

Age

Male

Female

Significant increase beyond age

-

-

Over 758 of cases occur between ages

55-80

55-85

Etiology

The etiology of most thyroid cancer as it occurs in the United States today is unknown, but information is available with regard to etiologic or predisposing factors in some cases.

Goitrogenic Factors

The most important goitrogenic factor is iodine deficiency of greater or lesser degree which at one time was such an ubiquitous problem. It is of far less importance in the United States now than formerly, but there still exist "goiter belts" away from seacoasts where the incidence of relative iodine lack and consequent thyroid abnormalities is still rather high. The frequencies of iodine deficiency, hyperplastic changes in the thyroid gland including goiter, and thyroid cancer tend to parallel each other. An attempt will be made to deal with some aspects of this rather thorny relationship between benign and malignant thyroid disease later in this chapter (p. 111).

Radiation

The consensus now is that there is an increased incidence of thyroid cancer among those individuals who received x-ray therapy to regions adjacent to the thyroid (e.g., thymus gland) in childhood and young adult life.

Pathology

Some departure from the conventional presentation is made necessary by the distinctive clinical behavior of certain subtypes of thyroid cancer. These distinctive qualities of thyroid cancer are listed in Table 2.

The vexing and important problem of the relationship of nodular goiter to thyroid cancer will be dealt with separately (p. 110) following a consideration of the usual clinical manifestations of the disease.