52 - Thyroid and other endocrine glands

Summary

Introduction

Malignant tumors of the thyroid, although comparatively rare, representing 1–2% of all cancers, are the commonest cancers of the endocrine system. A number of rare tumors arise in other endocrine glands, notably the pituitary, the adrenals and pancreas.

Histology, classification and diagnosis

Thyroid tumors can be classified into several different histological types which show variations in geographical distribution (Correa et al., 1969). In Colombia, papillary carcinoma predominates in areas where goiter is non-endemic, but follicular and anaplastic tumors are more common in goitrous areas, as in Israel, Norway, and Finland. Certain tumors (adenomas) of the thyroid are believed to be precursors of carcinoma and in view of their premalignant potential, benign adenomas are regarded with some suspicion. The differential diagnosis of thyroid adenoma and well-differentiated cancer is subjective and often difficult.

Pituitary tumors, although mostly histologically benign, may present as intracranial neoplasms and be fatal. Different cell types are associated with a variety of characteristic endocrine disorders.

In the adrenal gland, tumors can arise in the cortex or medulla. The latter (pheochromocytoma) may occur as part of the MEN syndrome (pp. 193, 447).

Descriptive epidemiology

Unless stated, the following comments relate to thyroid cancer since due to their rarity, little is known regarding variation in non-thyroid endocrine tumors.