Study of Pathological Variations of Solitary Thyroid Nodule

Objective: To find out the incidence of malignancy in patient with solitary thyroid nodule. Methods: This cross-sectional study was carried out with 100 solitary thyroid nodular patients who admitted in Otolaryngology & Head-Neck Surgery Department of Sir Salimullah Medical College Mitford Hospital (SSMCMH) & Bangabondhu Sheikh Mujib Medical Univercity (BSMMU), Dhaka, from July 2012 to December 2013,where all patients were admitted through out patient department.All patients were selected as per described criteria from the Department of Otolaryngology & Head-Neck Surgery,SSMCMH & BSMMU.Diagnosed the cases by detail history,clinical examination,investigations,analysed data presented by various tables,figures. Results: In this study mean age of the patients of solitary thyroid nodule was 35.613.54 years and the highest frequency (38%) was within 21-30 years of age with female predominance(78%).Thyroid swelling was the common presentation in all9100%) cases, some patients also presented with other symptoms like cervical lymphadenopathy 13(13%) cases, dysphagia 1(1%), dyspnoea 1(1%), hoarseness of voice 1(1%) case & no bone metastetic found.In this series of solitary thyroid nodules constituted 73% firm, 6% hard and 11% cystic. Malignancy was found more in firm nodule 13(72.22%).Isotopes scanning of the thyroid gland were done to see the functional status of the nodule. We found most 96(96%) of the nodules were cold & 4(4%) were warm nodule & no hot nodule found. In our study out of 96 cold nodular goiters we found 18(18.75 %) malignant & no malignant case found from rest of 4 warm cases. In our study, out of 89 solid nodule 72(80.89%) were benign & 17(19.10%) nodule were malignant and out of 11 cystic nodule 10(90.9%) were benign & 1 (9.1%) was malignant. In this study, most of the benign & malignant nodules were predominantly solid. Study showed the malignancy is significantly (p<0.001) more in solid than cystic solitary thyroid nodule. Final diagnosis in this study was on the basis of histopathological reports record. Out of 100 cases, 54 cases (54%) were proven as nodular goitre & 2 % were thyroiditis in non-neoplastic lesion & in neoplastic lesion we found 26(26%) 1. Junior Consultant, ENT&HNS, General Hospital, Narayanganj, Bangladesh 2. Ex.Professor & Director, National Institute of ENT, Tejgaon, Dhaka , Bangladesh 3. Assistant professor, Dept. of ENT & HNS, Rangpur Medical College, Rangpur, Bangladesh 4. Junior Consultant, National Institute of ENT,Tejgaon,Dhaka ,Bangladesh 5. MO, ENT & HNS, Sir Salimullah Medical College Mitford Hospital.Dhaka 6. Professor & Head,Dept. Of ENT & HNS, Sir Salimullah Medical College Mitford Hospital.Dhaka Address of Correspondence: Dr.Abdullah Al Mamun, Junior Consultant, ENT&HNS, General Hospital, Narayanganj, Bangladesh, E-mail:mamunmail24@gmail.com, Cell+88-01711457470. Original Article Bangladesh J Otorhinolaryngol 2018; 24(2): 105-114


Introduction
Thyroid gland and its enlargement are known since the time of Hippocrates. Among the endocrine organs, diseases of the thyroid gland are the most common. A good number of diseases affect the thyroid gland and almost all of them presents with nodular thyroid swelling. Nodular goiter remains a problem of enormous magnitude all over the world, although exact data on incidence and prevalence are unavailable. In our country the national prevalence rate is 10-15%, which indicates, the whole country is endemic. The endemicity varies from one place to another. The highest prevalence rate in Bangladesh is in the district of Rangpur and Jamalpur, the range varies from 21-30%. Nodular thyroid disease is more prevalent than diffuse goitre. In a report from the thyroid clinic, Bangabondhu Sheikh MujibMedicalUnivecity, Dhaka 32.67% of all thyroid patients had solitary nodules 1 .
The solitary or isolated thyroid nodule may be defined as a discrete swelling in an otherwise impalpable gland. It is usually a benign lesion. It is common in clinical practice. The swelling is often noticed accidentally by the patient or drawn to her attention by a family member, neighbor, or a friend. The nodule may also be encountered as an incidental finding when a patient is examined for some unrelated disease. About was benign (follicular adenoma) and 18(18%)  70% discrete thyroid swellings are clinically isolated. Thyroid nodules are common and are among 3-4% of the adult population in the UK and USA. They are 3-4 times more frequent in women than men. A nodule may be adenoma, cyst, multinodular goiter, thyroiditis and thyroid cancer 2 .
The importance of solitary thyroid nodule lies in the significant risk of malignancy compared with other thyroid swelling. Many studies have been published on the risk of malignancy in patients with thyroid nodules; these studies show that the risk of malignancy is low, approximately 5%, unless the patient has an underlying risk factor, such as a history of external neck irradiation 3 . If imaging investigations shows the nodule to be truly solitary, then the likelihood of it being malignant increases to about 5-20% 4 , of which papillary carcinoma comprises about 80%, follicular carcinoma 10% and medullary carcinoma 5% 5 , but in another study it showed papillary carcinoma comprises about 60% and follicular carcinoma 18% 6 .
Screening of large numbers of patients previously unsuspected of having goiter suggests that the incidence of the isolated thyroid nodule in the general population may be of the order of 4-7% 7 . A thyroid nodule larger than 1 cm in diameter is usually palpable. However, the detection of a nodule by palpation also depends on its location within the thyroid gland, on the structure of the patient's neck and on the experience of the examiner.
It has been estimated that palpable thyroid nodules are present in 4-7% of the population, but when examined by ultrasound, as many as 50-70% of subjects with no history of thyroid disease have been found to have incidentally discovered thyroid nodules, many of which are not palpable 8 . In addition, nodular thyroid disease is more common in the elderly, a population subgroup, which is steadily increasing 9 .
Laboratory investigations other than FNAC have limited role in finding out the nature of thyroid swelling. Isotope scan can demonstrate the functioning capacity of the nodule but cannot predict the histopathological character 10 .
Fine needle aspiration cytology (FNAC) is considered as the most reliable test for the diagnosis of thyroid nodules 11 . Many investigators have tried to point out few ultrasonographic features in order to identify those lesions, which are at a higher risk of malignancy, especially in non-palpable thyroid nodules 12 . Pre-operative assessment of thyroid nodules is generally performed by radio-nuclide scanning and fine needle aspiration (FNA). FNA biopsy is described as the most preferred test that has improved selection of patients for thyroid surgery. Several studies have concluded that the risk of thyroid cancer is less with multiple nodules than with solitary nodules 13, 14 but other studies have not found any difference in risk 15 . It is becoming increasingly clear that high-resolution ultrasonography is better than physical examination 9 or other imaging techniques 16 in detecting thyroid nodules.
This study has been carried out to find out the relative frequency of pathological types, incidence of malignancy in solitary thyroid nodule and its age & sex variation. This study also carried out to review the existing protocol for the management of solitary thyroid nodules in our country and to assess the accuracy of the available diagnostic modalities for appropriate selection of patients Data were processed and analyzed by using computer based programmed SPSS-16 (Statistical Package for Social Sciences). The quantitative data were analyzed by mean, standard deviation. The qualitative data were analyzed by Pearson Chisquare(x 2 ) test with 95% confidence interval to make inference.        21,22 .Where duration of swelling prior to the presentation was from 6 months to 3 yrs 17 .Nodular goiter with large swelling may be associated with difficulty in respiration or rarely in deglutition which is due to pressure on trachea or oesophagus 23 .

Results
In this series we have seen that nodules were found more in right lobe than left. There is yet no reported predilection for any specific site and no reason has been put forward for such a predilection. Similar findings were noted by many authors 24,25 .We found 56 nodules in right lobe, 38 nodules in left lobe, 4 nodules in both lobes and 2 nodules in the junctional region between isthmus and one lobe.
Firm nodules are the commonest form of solitary thyroid nodule. In this series of solitary thyroid nodules constituted 73% firm, 6% hard and 11% cystic. Malignancy was found more in firm nodule 13(72.22%).Islam  ) and cystic (11.02%). Malignant lesion was more common in hard nodule (70%).)Here hardness of nodule was due to malignancy and inflammatory conditions. Among 6 hard nodules, 4 were diagnosed as malignancy and 2 were diagnosed histopathologically as thyroiditis. So hardness in not conclusive but an important indication for malignancy. Hardness and irregularity, due to calcification, may simulate carcinoma 6 .
Investigations are essential to establish preoperative physical, function status and cytopathological nature of solitary nodule of thyroid 26 .
All patients of this study have done thyroid hormone profile and show value within normal limit. Isotopes scanning of the thyroid gland were done to see the functional status of the nodule. We found most 96(96%) of the nodules were cold & 4(4%) were warm nodule & no hot nodule found. In our study out of 96 cold nodular goiters we found 18(18.75 %) malignant & no malignant case found from rest of 4 warm cases.In a study showed that on thyroid scan out of 40 patients (80%) having cold nodule &10 patients (20%) had hot nodule 27 . Most of the nodules were cold (66.10%) among them 25.6% cases were malignant, followed by warm (30.5%) and hot (3.3%) 28 .
Fine needle aspiration cytology (FNAC) is a very important, highly sensitive and minimally invasive preoperative diagnostic tool 23 . According to a study FNAC is a gold standard for preoperative assessment of thyroid nodules. Early and accurate diagnosis reduces surgical intervention, morbidity and mortality 29  Our study correspond with a study where he showed of cystic thyroid lesions, 4% were simple cysts, 82% were degenerating benign adenomas or colloid nodules and 14% were malignant compared with 23% of solid lesions that were malignant 33 . Cathy Crenshaw Doheny also mentioned In a web journal found that a solid thyroid nodule is more likely than a cystic nodule to be malignant 34 . More than 90% of all solid nodules, however, are benign. A study showed 9% incidence of malignancy in solid nodules & no malignancy in cystic nodules 35 .
Whereas other found incidence of carcinoma in cystic lesion <2% 36 .
As this study had been carried out over a limited period of time with a limited number of patients, it could not have been large enough to be of reasonable precision. All the facts and figures mentioned here may considerably vary from those of large series covering wide range of time, but still then, as the cases of this study were collected from tertiary level hospitals in our country, this study had some credentials in reflecting the facts regarding distribution and type of malignancy in solitary thyroid nodules.

Conclusion
We have observed worldwide malignancy in STN ranging from 16-30% 37 .We found in our series containing 18% malignancy in solitary thyroid nodule. So significant percentage of malignancy in STN is very important though it is a small nodular lesion. As small lesion of STN sometimes is overlooked so it is an important message to our fellows and practitioners to get appropriate medical attention for early diagnosis & proper management to reduce the morbidity and mortality.