Pattern of Malignancy in Thyroid Swelling

: Background: Incidence of thyroid malignancy is increasing day by day in thyroid swelling. The exact cause of cancer is not known. But there are few predisposing factors in genesis of thyroid malignancy such as age, sex, geographical distribution, familial predisposition, radiation exposure, pre-existing thyroid disease. Papillary thyroid carcinoma is most common among all thyroid malignancy with high incidence of lymph node metastasis. The aim of this study is to find out the pattern of malignancy in thyroid swelling. Methods: This cross-sectional observational study was done in department of Otolaryngology-Head neck surgery; Dhaka Medical College Hospital for 6 months. 50 Patients with thyroid swelling undergone operative management were included. Results: Results of this study showed that the highest numbers of patients were in 31-40 years of age group numbering 20 (40%). There were 42 females comprising 84% and males comprising 8 (16%) with female to male ratio 5.25:1. Among the thyroid swelling 35 (70%) cases were solid & 15 (30%) cases were cystic and 38 cases were non-neoplastic and 12 cases were neoplastic. Among the 12 cases 7 cases were malignant. Papillary carcinoma was predominant having 6 (85.7%) cases and Follicular carcinoma was in 1 (14.28%) case and out of 7 cases metastatic cervical lymph node was in 1 (14.28%) case which was from papillary carcinoma. Conclusion: Incidence of thyroid malignancy in thyroid swellings is high. Male patients with thyroid swelling has more chance of thyroid malignancy and papillary thyroid carcinoma is the commonest of all thyroid malignancy with cervical neck node metastasis.


Introduction:
Thyroid swelling (goiter) is a worldwide problem. Iodine deficiency is the main cause of thyroid swelling. Others cause may be familial, inflammatory, neoplastic 1 .
Thyroid cancer is most common among all endocrine malignancy 2 . It is accounting for 1% of all malignancy 3 . The worldwide prevalence of goiter in general population is estimated at 4-7%. Incidence of malignancy in goitrous thyroid is about 10% 4 . It is postulated that goitrous thyroid is precursor lesion to the development of malignant diseases 5 . An increased incidence of thyroid carcinoma has been noted in endemic goiter zones 6 . Frequency of carcinoma is two times more in solitary thyroid nodules than multinodular goiter. Male patient with solitary thyroid nodules showed high incidence of malignancy 7 .
Exact cause of cancer is not known but there are few predisposing factors which favors in genesis of thyroid malignancy such as age, sex, Geographic distribution, familial predisposition, radiation exposure, preexistent thyroid disease 8 . Differentiated thyroid carcinoma e.g. papillary carcinoma and follicular carcinoma are more common. Both are arising from thyroid follicular cell 9 . Papillary carcinoma is about 80% among all thyroid malignancy. It occurs in all age groups and is only thyroid cancer of children 10 . It is firm, encapsulated, multicentric and frequently involves both lobe. It has high incidence of lymph node metastasis 11 . May present as occult carcinoma as lymph node metastasis without palpable thyroid gland 12 . Follicular carcinoma commonly occurs in older age usually between 50-59 yrs. It is accounts for 10-20% of all thyroid malignancy. Lymph node metastasis is less common.
Medullary thyroid carcinoma is about 5% of all thyroid malignancy arise from perifollicular cell (c cell). It may occur as part of MEN syndrome, as familial NON MEN disease or it be sporadic. Lymph node metastasis are common. Anaplastic carcinoma are common in elderly. It is more aggressive and highly metastatic potential. Majority of patient with anaplastic carcinoma usually die within 6 months 12 . Primary thyroid lymphomas are uncommon. Usually high-grade B cell lymphoma tends to occurs middle aged and older patient.
Exact incidence of thyroid cancer in Bangladesh is not known but an estimate of 2.58% of 2,629 patients attending at the Institute of Post-graduate Medicine and Research (IPGMR, Currently BSMMU) from January 1994 to June 1995 were suffering from thyroid carcinoma 13 . Moreover, incidence of malignancy of solitary thyroid nodule is significantly high in Bangladesh (18.65%) as like others country 14 .

Methods:
Study design: Cross sectional observational study.

Place of study: Department of Otolaryngology, Dhaka Medical College Hospital, Dhaka
Study periods: Study was conducted from June 2019 to November 2019.
Study Population:Patients with thyroid swelling undergone operative management were included. Total 50 cases were selected after careful history taking, thorough general, local examination and appropriate investigations fulfilling inclusion and exclusion criteria.
Sample size: 50 samples were taken in this study.

Results:
In this study 50 cases of thyroid swelling were analyzed to find out the incidence of malignancy. The result and observation of the study are shown below.

Discussion:
The aim of this study was to find out the incidence of malignancy among thyroid swellings in hospitalized patients and 50 cases of thyroid swelling were studied in Dhaka Medical College Hospital during study periods.
In this study highest number of patients were in the 31-40 years of age group numbering 20 (40%) followed by 15 (30%) in the 21-30 years age group. Age distribution of this series more or less in general agreement with similar reports in literature 15,16 . The youngest patient of our series was a girl of age 11 years, suffering from papillary carcinoma. The oldest patient of our series was a male of age 59 years, a case of follicular carcinoma.
The extreme of ages shows more chance to be malignant and less chance to be benign thyroid disease 17 . The youngest and oldest patient of our study have been suffering from malignant thyroid disease that correspond to that study.
In this study out of 50 cases, 42(84%) were female and 8(16%) were male. Female to male ratio is 5.25:1. It is due to thyroid disorder is more common in female than male 18 .
In our study, we have detected one case with cervical lymphadenopathy along with goitre which was diagnosed as malignancy. In this study we have found 4 cases suffering from dysphagia and 1 case suffering from dyspnoea, all are diagnosed as multinodular goitre. Multi-nodular goitre with large swellings may be associated with difficulty in respiration or rarely in deglutition which is due to pressure on trachea or oesophagus 19 .
In this study we found solitary thyroid nodule in 30%, multinodular goitre in 68% and diffuse goitre in 2%. All solitary thyroid nodule is not a single clinical entity 16 . So, it is very difficult to comment regarding the nature of solitary nodule purely on the basis of clinical ground 20 . But hoarseness of voice, hard irregular nodule, palpable cervical lymph node, extreme of ages, male sex is always suspicious for malignancy in solitary nodule 21 .
Solid nodules are the commonest form of solitary thyroid nodule. In this series solid nodules were 70%, 30% were cystic as reveled by USG 22 .
Fine needle aspiration cytology (FNAC) is very important, specific, most sensitive, minimally invasive preoperative diagnostic tool 23 . In this study 76% cases were colloid goitre 12% papillary carcinoma and 12% were follicular neoplasm. FNAC cannotdistinguishedfollicular carcinoma and follicular adenoma. FNAC diagnosis of this series is supported by postoperative histopathological reports.
Final diagnosis of this study was on the basis of histopathological confirmation. Out of 50 cases, 37 cases (74%) are proven as colloid nodular goitre on histopathology and it is  24 . whereasanother Bangladeshi study found a higher incidence of 21.11% 25 . It can be explained by the fact that our study was carried out in only hospitalized patients in a short span of time.

Conclusion:
In this study, incidence of thyroid malignancy among thyroid swellings in hospitalized patients was 14% .Incidence was higher in male 25% than female 11.9% and also higher in age below 20 and above 50 years. Papillary carcinoma was most common pattern. It can be concluded that as significant proportion of thyroid swellings (in this study 14%) may be malignant. Chance of malignancy is higher in extreme age groups, male sex with goitre. So, it should get serious medical attention.