Review of the histological variants of papillary thyroid carcinoma and assessment of the prognostic factors

Abstract

The incidence of thyroid cancer has increased in many parts of the world and in Sri Lanka it is the second most common malignancy in females. There are several risk factors of thyroid cancer out of which exposure to radiation, genetic mutations and Hashimoto’s thyroiditis are regarded as the important associations. Papillary carcinoma is the most common cancer of thyroid gland. There are several histological variants of papillary carcinoma with different biological behavior and outcome. Aim of the study was to review the histological variants and assess the prognostic factors in a cohort of papillary carcinoma. A retrospective study done over period of 4 years in 3 specialized surgical centers. There were 91 cases of papillary carcinoma in which the histological diagnosis was reviewed and confirmed. In the study population female to male ratio was 9:1 and the mean age of papillary carcinoma was 41 years. Gross assessment showed that 89% of tumours were solid and 11% were cystic. In 29% of cases the tumour was multifocal. The most common histological types were papillary carcinoma, conventional type (24%) and the follicular variant which accounted for 35% of the cases (p< 0.05). Non-neoplastic thyroid tissue was within normal limits in 47 % and in 36 % there was background chronic thyroiditis. Lymph nodal involvement was seen in 22% and 6% of cases had distant metastasis. It is important to identify the histological variants of papillary thyroid carcinoma as some of the types are associated with a poor outcome. Nodal involvement and distant metastasis showed a statistically significant association with the aggressive patterns (p< 0.05) of papillary carcinoma