Abstract
A significant increase in incidence of papillary thyroid carcinoma (PTC) has been noticed in recent decades worldwide. This is due to advances in medical surveillance, increased use of ancillary tests, and a minor component due to over diagnosis of PTC. Follicular variant of papillary thyroid carcinoma (FVPTC) is the second most common variant of PTC and comprises about 23-41%. It is difficult to diagnose histologically when the distinctive nuclear features are either not well developed or present focally within the lesion. Several immunohistochemical markers (CD56, HMCK, GAL3, HBME-1 and CK19) either alone or combined in panels can be used to improve diagnostic accuracy. This study was aimed to differentiate FVPTC from other follicular patterned lesion of thyroid by histopathology and immunohistochemistry (IHC). A total of 50 histologically diagnosed cases of thyroid neoplasm were studied. The neoplastic cases included 40 cases of follicular variant papillary carcinoma (FVPC), 04 classic papillary carcinoma (PTC), 04 follicular carcinoma and 02 follicular adenoma. All cases were evaluated by IHC for the expression of CD56 and CK19 antibody. In case of FVPTC (n=40), 21 cases (52.5%) were CK19 positive and CD56 negative as expected. Both markers were found positive in 06 (15%) cases and CD56+ alone was found positive in 11 (27.5%) cases of FVPTC, and a finding that goes against the diagnosis of FVPTC. The histopathological slides of these cases were reviewed and findings were recorded. All cases (n=4) of classic PTC were CK19 positive and 03 (75%) cases were found CD56 negative. Diagnoses of thyroid follicular lesions are primarily based on histological and cytomorphological criteria. However, there was a subset of follicular patterned tumors like FVPTC which lack unequivocal features of malignancy. Immunohistochemistry can improve diagnostic accuracy but needs additional studies for controversial cases. It may be considered these lesions as differentiated tumor of uncertain malignant potential (WDT-UMP) to avoid the using term carcinoma. Additional studies are needed for establishing more precise morphologic criteria and for identifying useful markers for differentiating benign from borderline or malignant thyroid lesions.
Highlights
Thyroid cancer represents 1.5% of all cancers.[1]
A total of 40 cases of histologically diagnosed follicular variant of papillary thyroid carcinoma with proper clinical information from all ages and both sexes were included. Another 10 cases of follicular carcinoma (n=4), follicular adenoma (n=2) and classic papillary carcinoma (n=4) were included for comparison in immunohistochemical study to see the pattern of expression of used antibodies in these tumours
Size of the tumor ranged from 0.7cm to 6.5 cm with a mean of 3.1±1.7 cm in cases of Follicular variant of papillary thyroid carcinoma (FVPTC)
Summary
Thyroid cancer represents 1.5% of all cancers.[1]. Butit is the commonest endocrine cancer accounting for 92%.2 The annual incidence of thyroid cancer varies from 0.5 to[10] per 100,000 populations worldwide. Thyroid cancer represents 1.5% of all cancers.[1] Butit is the commonest endocrine cancer accounting for 92%.2. The annual incidence of thyroid cancer varies from 0.5 to[10] per 100,000 populations worldwide. Exact incidence of thyroid cancer in Bangladesh is not known. Studies on histopathological features revealed 85-90 % of their study cases were papillary thyroid carcinoma (PTC) and 10-15 % were follicular carcinoma.[4] Incidence of these two types of carcinoma increased in many places around the world over the past three decades.[5] This is due to advances in medical surveillance of impalpable nodules and increased emphasis on ancillary tests.[6] Such increase reflects a minor component of over diagnosis of PTC. It is clear that some cases do raise controversy as being PTC or non PTC.[7]
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