Malignant tumours

Malignant tumours

The vast majority of primary malignancies are carcinomas derived from the follicular cells ( Table 55.6 ). Such tumours were thought of as di ff erentiated (papillary , follicular and Hürthle cell) and undi ff erentiated (anaplastic). However, now an intermediate class of ‘poorly di ff erentiated carcinoma’ is recognised, which is likely to represent a state of dedi ff erentiated – between classic di ff erentiated and undi ff erentiated diseases. The parafollicular C cells can undergo malignant transfor mation into medullary carcinoma, and thyroid lymphoma is another primary thyroid malignancy . In addition, the thyroid can be involv ed by direct spread from surrounding structur (larynx and oesophagus) or metastases (most commonly from renal cell carcinoma). Lymph node and blood-borne metas tases of thyroid cancer occur primarily to bone and lung and may be the mode of presentation ( Figure 55.22 ). Aetiology of malignant thyroid tumours The great majority of thyroid cancers have no known aetiolog ical factor. The most important identifiable aetiological factor in di ff erentiated thyroid carcinoma (particularly papillary) is irradiation of the thyroid under 5 years of age. In the town of Gomel, Ukraine , the incidence of childhood thyroid cancer rose from <1 per million to 96 per million following the Chernobyl nuclear disaster. Short latency aggressive PTC is associated with the ret / PTC3 oncogene and later developing, possibly less aggres sive, cancers with ret / PTC1 . The incidence of follicular carci noma is high in endemic goitrous areas, possibly because of TSH stimulation. Malignant lymphomas sometimes develop in autoimmune thyroiditis, and the lymphocytic infiltration in the autoimmune process ma y be an aetiological factor.

Figure 55.21 Isolated swelling in the upper pole of the right thyroid lobe.

Malignant tumours

The vast majority of primary malignancies are carcinomas derived from the follicular cells ( Table 55.6 ). Such tumours were thought of as di ff erentiated (papillary , follicular and Hürthle cell) and undi ff erentiated (anaplastic). However, now an intermediate class of ‘poorly di ff erentiated carcinoma’ is recognised, which is likely to represent a state of dedi ff erentiated – between classic di ff erentiated and undi ff erentiated diseases. The parafollicular C cells can undergo malignant transfor mation into medullary carcinoma, and thyroid lymphoma is another primary thyroid malignancy . In addition, the thyroid can be involv ed by direct spread from surrounding structur (larynx and oesophagus) or metastases (most commonly from renal cell carcinoma). Lymph node and blood-borne metas tases of thyroid cancer occur primarily to bone and lung and may be the mode of presentation ( Figure 55.22 ). Aetiology of malignant thyroid tumours The great majority of thyroid cancers have no known aetiolog ical factor. The most important identifiable aetiological factor in di ff erentiated thyroid carcinoma (particularly papillary) is irradiation of the thyroid under 5 years of age. In the town of Gomel, Ukraine , the incidence of childhood thyroid cancer rose from <1 per million to 96 per million following the Chernobyl nuclear disaster. Short latency aggressive PTC is associated with the ret / PTC3 oncogene and later developing, possibly less aggres sive, cancers with ret / PTC1 . The incidence of follicular carci noma is high in endemic goitrous areas, possibly because of TSH stimulation. Malignant lymphomas sometimes develop in autoimmune thyroiditis, and the lymphocytic infiltration in the autoimmune process ma y be an aetiological factor.

Figure 55.21 Isolated swelling in the upper pole of the right thyroid lobe.