Chronic lymphocytic thyroiditis is an autoimmune entity where in the thyroid follicles are rapidly destroyed. The cytological markers include lymphocytic infiltration of the interfollicular space, invasion of follicles by the lymphocytes giving a fire-flare appearance characterized by eosinophilic vacuolated cytoplasm and later, total destruction of follicles. In the long run, the follicular architecture is totally destroyed and replaced by fibrosis. The active phase of disease is transient with clinical manifestations of thyrotoxicosis while the evolution phase and destructive phase manifest with subclinical or overt hypothyroidism. The present study was designed to correlate the cytological grades of thyroiditis with rest of the parameters and to define the grading criteria for thyroiditis on cytological material.
Our patients were mainly young females. This is in contrast to a previous study [9
] from United Kingdom in which the patients were mainly older women with mean age at diagnosis being 59 years. This disparity may be due to occurrence of LT in young patients in iodine deficient areas such as ours, while it occurs in older individuals in iodine sufficient areas [2
]. Most of our patients had symptoms of hypothyroidism with a diffuse goiter although nodular presentation was also noted in few cases. Previous authors have also documented nodular presentation in LT which might mimic malignancy clinically [11
]. Friedman et al [12
] found nodular presentation in as many as 80% of their patients. The nodules represent early stage of the disease when the clinical and hormonal changes are not established. In our study the incidence of nodularity was low as the patients had either sub clinical or clinical disease, at the time of presentation. TSH was elevated in all but one case with either decreased or normal T3, T4. The normal T3, T4 levels in the presence of elevated TSH indicate sub clinical hypothyroidism (SCH). The incidence of SCH was higher in our study compared to a study by Bagchi et al [13
] who found subclinical disease in 8–17% of their subjects. Higher incidence of overt or subclinical hypothyroidism in our subjects is understandable as they were from a clinic population where individuals with subtle or significant symptoms are expected to seek medical advice. One of our patients was hyperthyroid with high T3, TSH and uptake levels and increased TMA titers. Her thyroid aspirate showed grade III thyroiditis. This phenomenon known as thyrotoxicosis is due to acute aggravation of thyroid autoimmunity induced destruction of follicles.
The RAIU values were normal or low in majority of the patients as was seen in previous studies [12
]. The low uptake values indicate the destruction of gland by the autoimmune process. The raised RAIU in some may be due to iodine deficiency.
Serum TMA titers were elevated in more than half of our patients in contrast to published reports where the serum TMA titers were elevated in up to 95% patients [14
]. Such variations are explained by chance inclusion of patients early in the course of disease as intrathyroidal immune destruction occurs much earlier to serological evidence and inclusion of non-immune LT in the patient group [15
In this study the sonographic goiter was found in less number of patients as compared to those with clinical goiter. This discrepancy may be due to lack of reference values in radiology for Indian population. Also it has been shown that thyroid volume varies significantly with factors like age, sex, height, weight and place of living [16
]. Hence the western data cannot be extrapolated to Indian population and may be the source of lower prevalence in our study. Micronodularity was the most frequently observed feature and showed a high positive predictive value which is in keeping with the observations in previous studies [18
]. Fifty percent patients showed septations on USG indicating fibrosis and hence disease of some duration. The low prevalence (4.16%) of diffuse hypoechogenic enlargement of thyroid gland in comparison to previous studies (18.5–95%) [8
] may also be due to relatively small number of patients in our study group. The USG helps not only in diagnosis of the condition but also in selecting the patients with suspicious nodules for work up for malignancy [20
]. In the present study no neoplastic lesion was found amongst the cases studied.
The diagnostic accuracy of fine needle aspiration cytology was high, multiple aspirations being helpful in almost all cases. The usefulness of increased number of aspirations has been stressed by Hamburger et al [21
] who found that as the number of aspirations increased, false negative results decreased. It has been emphasized in the past that in equivocal cases antibody testing is helpful, but if negative, a repeat FNA becomes the ideal choice [10
]. Only in one case with high serum TMA and TSH levels was the FNAC non-contributory due to inadequate material. A repeat sampling could not be performed in this case.
Grading of thyroiditis has been carried out on histological specimens in the past based upon number of foci of lymphocytes per standard representative section [23
]. On the other hand, grading on cytology smears has been done by only a few workers. In this study for the first time grading was carried out on FNAC smears using a set of predefined criteria. The grading using these criteria was found to be quite consistent and a high concordance rate was noted amongst the two observers. The grades were statistically correlated with clinical, biochemical, radionuclide, ultrasonographic features and serum TMA levels. It was observed that many of the patients with grade III disease had features of hypothyroidism and an altered hormonal profile however statistical correlation between the grades and above parameters was not significant. Kumar et al [10
] carried out correlation of severity of lymphocytic infiltration on smears with functional and antibody status however, in their study also no significant correlation was found. This may be due to the fact that grading on FNAC smears is also affected by other factors like dilution by blood, technique of the FNAC and the number of aspirations used. Furthermore, the aspirates are obtained from very tiny portion of thyroid gland and may not at times represent the pathology in entirety.
Therefore to conclude, lymphocytic infiltration of thyroid follicles is pathognomonic of lymphocytic thyroiditis and hence FNAC remains the gold standard for diagnosis. When graded into mild, moderate and severe the grades of thyroiditis correlate poorly with clinical, biochemical, ultrasonographic and radionuclide features and serum TMA levels.