Morphological pattern and frequency of thyroid tumors.

OBJECTIVE The present study was done to evaluate the frequency of thyroid cancer and to find out the prevalence of histological types of thyroid tumor with respect to age and sex group. SETTING This study included consecutive cases of malignant tumors of thyroid gland, which were diagnosed in the Department of Pathology at the Aga Khan University Hospital, Karachi during the period of three years (1995-1997). METHODS These cases were evaluated on H & E stained sections from paraffin embedded 10% buffered formalin fixed tissue blocks. Special stains and immunohistochemical analysis were performed whenever required. RESULTS A total of 8541 malignant tumors were diagnosed in a period of 3 years which included 103 (1.2%) cases of thyroid cancer. Thyroid tumors were more prevalent in females with female to male ratio of 2.6:1. Papillary carcinoma (69%) was the most common histological type of thyroid tumors, followed by follicular carcinoma (11.6%), medullary carcinoma (9.7%), anaplastic carcinoma (5.9%), non-Hodgkin's lymphoma (2.9%) and unclassified tumors (0.9%) in order of frequency. CONCLUSION Thyroid cancer was more common in females. Papillary carcinoma was the most common histological type of thyroid tumors in females as well as in males. Papillary carcinoma was more prevalent in third, fourth and fifth decades of life while follicular and anaplastic carcinomas were more frequent after the fourth decade of life.