There are some risk factors of thyroid cancer which are the following:
- Previous external irradiation
- History of cancer in the family
- predisposing genetic factors, ex. familial polyposis of the colon or Cowden's disease are associated with the risk of developing thyroid cancer
-resisting thyroid disease, a goiter, nodules
- hormonal factors and pregnancy, cancer is more present in females and so thyroid nodules develop more during pregnancy and with pregnancies and irradiations increases the risk.
- intake of excessive iodine (see populations of Hawaii and Iceland)
- factors linked to the diet
- 70% of the cancer is papillary carcinoma, especially in areas with sufficient iodine intake, and the best prognosis quoad vitam is the classical variant and the capsule form and follicular, ie the most defined histologically speaking forms. It is important to have performed a good histological examination and to have considered the invasion of the vascular structures, as in these cases the tumor is understood to be widespread at a distance. Hence the importance of a histological examination performed with all the attention that the case deserves.
-treatment must always be radical, with enlarged thyroidectomy, destruction of metastatic foci and radio-ablation!
cf The meaning of the goiter
| Epithelial thyroid tumors Benigni | Classification of Hedinger, Williams and Sobin |
| Follicular adenoma | Benign capsulated tumor with evidence of differentiated follicular cells |
| Malignant | |
| Papillary carcinoma | Malignant epithelial tumor with evidence of follicular differentiation, with papillary and follicular structures |
| Follicular carcinoma | Malignant epithelial tumor with follicular differentiation, without the typical characteristics of papillary carcinoma |
| Undifferentiated carcinoma | |
| Medullary carcinoma | Malignant tumor with evidence of differentiation of parafollicular C cells |
| Non-epithelial malignant tumors | |
| Sarcoma | Malignant tumor that has lost epithelial differentiation and with evident sarcomatose characteristics |
| hemangio-endothelioma | Highly malignant tumor with extensive areas of necrosis or hemorrhage and similvascular spaces delimited by cells with endothelial features |
| lymphoma | Tumor with positive immunohistochemistry for the common leukocyte antigen or similar antigens |
| Secondary tumors | With characteristics of the primary tumor |
Anatomo-pathological examination of a thyroid tumor aims to establish:
Benignity and malice, which is not always easy to discern
Distinguish papillary forms and follicular forms within differentiated carcinomas
Pay attention to the diagnosis of large cell anaplastic forms, medullary thyroid carcinomas
Understanding if a tumor is benign.
Benign thyroid tumors are clinically frequent and histological examination allows to distinguish follicular adenomas that are unique capsulans and nodules, which are non-capsulated and often multiple lesions. Follicular adenomas have a very visible microscopic appearance, and are formed from well-differentiated follicles or follicular cell girders to form rudimentary follicles. The most important criterion to understand if the lesion is benign is the NON vascular invasion, since in rat studies it is shown that follicular adenoma can be passed to carcinoma and also the same carcinoma often adenoma mask in some of its portions.
There are two histological forms of differentiated thyroid carcinoma: -The papillary carcinoma - Follicular carcinoma Papillary carcinoma In this context we distinguish the microcarcinomas, the intratiroidal carcinomas and the extratiroidal carcinomas. Microcarcinomas are tumors with a diameter of 1 cm or less, known as "occult carcinomas". These are small papillary carcinomas, in the form of sclerotic nodules of a few millimeters infiltrating the surrounding thyroid tissue, even in 5-35% of cases. It is a non-capsulated, partially necrotic, multifocal tumor, which affects both lobes. Papillary carcinomas contain papillae, each formed by a cell-connective-vascular axis with a typical nucleus. Follicles often filled with colloid with trabecular or lobular appearance are often associated. Psammomatosis bodies are calcium deposits in the context of these tumors. The nuclei of the tumor cells are more voluminous than the norm, pale, of the "frosted glass" type, with pseudoinclusions and lymphocytes around the tumor in the periphery. Lymph node invasion is frequent. The papillary tumor presents the follicular variant, ie a grossly capsulated tumor formed by follicles filled with colloid. Pulmonary metastases may be present but respond favorably to treatment. Diffuse sclerosing forms are rare and are observed in children and young adults, with global enlargement of the thyroid where the lobes are replaced by hard, sclerotic, fibrous tissue.
Classic histological types.
It presents itself as a unique, more or less capsulated thyroid nodule. Depending on the degree of invasion of the vessels and the capsule, the following are distinguished:
- Minimally invasive form
- Highly invasive form
The prognosis is aggravated depending on whether the vessels are invaded and also the degree of cell differentiation must be evaluated. The variants are:
Very rare clear cell carcinoma, with cytoplasmic vesicles that accumulate fat or glycogen, which simulate a renal tumor
Ossifile cell carcinomas are formed by follicular cells of large size with granular and eosinophilic cytoplasm and large nuclei with a prominent nucleolus. The granular appearance of the cytoplasm is related to the abundance of mitochondria. The oxyphilous cells are also present papillary carcinomas and benign diseases of the thyroid, such as nodular goiter, Basedow's disease, Hashimoto's thyroiditis
Other tumors
-Anaplastic carcinomas, which represent 5% and 15% of the cases of all thyroid cancers and are very aggressive cancers
- Medullary carcinomas that originate from parafollicular cells
- Rare cancers that include primary lymphomas