Histopathological pattern of malignancy in solitary thyroid nodule

Objective: To find out relative frequency and type of malignancy in solitary thyroid nodule (STN). Methods: This cross sectional study done in the Department of Otolaryngology Head & Neck Surgery, Dhaka Medical College Hospital (DMCH), Dhaka and Bangabandhu Sheikh Mujib Medical University (BSMMU), Dhaka during the period of July 2008 to June 2009. For this study, 118 patients who were admitted a case of solitary thyroid nodule for operation. Diagnosed the case by detailed history, clinical examination, investigations, analyzed data presented by various tables, graphs and figures. Total 118 patients were selected as per described criteria from the Department of otolaryngology and head-neck surgery DMCH & BSMMU, Dhaka from July 2008 to July 2009. Results: In this study of 118 patients of STN, majority of the patients were within 21-40 years age group with female predominance. In thyroid malignancy male and female ratio was 1:1.75. Among 118 cases of solitary thyroid nodule 22 cases were malignant. Out of 22 malignant cases, 16(73%) were papillary carcinoma, 4(18%) were follicular carcinoma and 2(9%) were anaplastic carcinoma. Thyroid swelling was the common presentation in all cases (100%), some patients also presented with other symptoms like cervical lymphadenopathy in 6 (5.08%) cases, dysphagia 2(1.69%) cases and hoarseness of voice 1(0.85%) case. Study showed very significant difference (p <0.01) between papillary and follicular carcinoma, highly significant difference (p<0.001) between papillary and anaplastic carcinoma. So, papillary carcinoma was more common among all thyroid malignancies in patients with solitary thyroid nodule. Conclusion: Significant proportion of solitary thyroid nodule (18.65%) was malignant. So, careful assessment of thyroid nodule is important for early diagnosis.


Introduction:
Clinically recognized thyroid carcinoma constitutes less than 1% of human malignant tumours 1 . Among them differentiated thyroid carcinomas are the common variety. There are two types of differentiated thyroid carcinoma, papillary and follicular carcinoma.
True solitary thyroid nodule (STN) occurs in 4-7% of the adult population. They are present in 5% of persons at an average of 60 years. They are more common in female (6.4%) as compared to male (1.5%) and this predisposition exists throughout all age groups 2,3,4 . In general, a nodule of 1.5 cm diameter is detectable by palpation. Thyroid nodule could be adenoma or malignant neoplasm. Most thyroid nodules are benign hyperplastic lesions, but 10-23% of these are malignant neoplasm in nature 5,6 .
The incidence of thyroid carcinoma varies in different series 7 . The presence of a solitary thyroid nodule is a risk factor for malignancy. The incidence of malignancy within a clinically solitary thyroid nodule varied widely in the literature i.e. from 10-23.7% 5, 6 .
FNAC In highly sensitive for diagnosis in most cases and plays a crucial role in the selection of patients for operation. It is simple, quick to perform, readily repeated, an excellent patient compliance 8 .
The importance of solitary thyroid nodule lies in the significant risk of malignancy compared with other thyroid swelling. So, proper diagnosis and appropriate treatment of thyroid nodule is mandatory.
The attending patients of these hospitals are from all the corners of the country (both endemic and non endemic area) which are more or less representative of all the head-neck cancer population of Bangladesh.
This study try to correlate the pattern of malignancy in solitary thyroid nodule along with socio-demographic and influence of defined risk factors.

Discussion:
Carcinoma of the thyroid is the most common malignancy of endocrine system comprises 0.6% and 1.6% of all cases of malignant neoplasm in men and women respectively 5 .
Mean age of the patients of solitary thyroid nodule was 32.54±2.97 years and the highest frequency 54(45.76%) was in 31-40 years. This is similar with the other studies 2,3,4 . The youngest patient in this study was a girl of 12 years with a papillary carcinoma and the oldest patients was a lady of 65 years with anaplastic carcinoma.
In this series, out of 118 patients, male were 38(32%) and female were 80(68%). Male female ratio is 1: 2.1. This ratio was shown 1:3 by other series 6 -10 . The female preponderance is reflected in all studies including the present.
In this series we have seen that right lobe is slightly more affected than left lobe. There is yet no reported predilection for any specific site and no reason has been put forward for such a predilection. We found 55 nodules in right lobe, 50 nodules in left lobe, 8 nodules in isthmus and 5 nodules involving the isthmus and one lobe.
All patients of this study have done thyroid hormone profile and show value within normal  This study showed significant difference (p <0.01) between papillary and follicular carcinoma, highly significant difference (p<0.001) between papillary and anaplastic carcinoma. So, papillary carcinoma was more common among all thyroid malignancies in patients with solitary thyroid nodule.

Conclusion:
Significant proportion of solitary thyroid nodule (18.65%) was malignant. So, careful assessment of thyroid nodule is important for early diagnosis.