الفهرس 
IntroductionOnly 14 pages are availabe for public view
 |  | from | 198 |  |  |
| | | from | 198 | | |
Abstract
The incidence and mortality of thyroid carcinomas are rapidly rising worldwide accounting to around 3.4% of newly diagnosed cases of cancer in 2017 (Siegel et al., 2017). The global thyroid cancer burden is estimated, according to the National Cancer Institute statistics in 2017, to have increased to 56,870 new cases and 2010 deaths (Siegel et al., 2016). The most common histopathological type is papillary thyroid carcinoma (PTC) which accounts to around 60% to 80% of all thyroid carcinomas in adults (Halkova et al., 2016; Haugen et al., 2015).
In Egypt, according to the National Cancer Registry Program, thyroid cancer is the fifth most frequent cancer in females accounting for 3.6% of all malignancy in women. The estimated number of thyroid cancer in Egypt in 2015 was 2448 cases of whom 1876 were females (Amal et al., 2014).
The diagnosis of PTC depends upon the architectural characteristics together with nuclear clearing, overlapping, intranuclear grooves and intra-nuclear pseudoinclusions. The diagnosis of PTC based on these histological features is still the most effective current method in classical unequivocal cases (Baloch and Li Volsi, 2008). However, some of these morphological features can exist in other benign and malignant thyroid lesions. This creates some diagnostic challenges and sometimes significant biases.
The encapsulated follicular patterned nodule with PTC like nuclear features is a newly implemented category in the borderline thyroid lesions. It is defined as non-invasive follicular tumor with papillary nuclear features (NIFTP) (Nikiforov et al., 2016). This category is among the cases which creates a significant dilemma with diagnostic challenge to differentiate it from follicular adenoma.
Benign thyroid lesions with papillary hyperplasia and focal PTC-like nuclear features are other lesions which also cause diagnostic difficulties (Bychkov et al., 2016).
Accordingly, TROP-2 has recently emerged as a new immunohistochemical marker with promising results in the diagnosis of papillary thyroid carcinoma (Simms et al., 2016) and it may be useful to differentiate it from other benign thyroid lesions (Bychkov et al., 2016).
The trophoblast cell surface antigen (TROP-2) is a human trophoblastic transmembrane glycoprotein, initially recognized in choriocarcinoma and human trophoblast cells (Zhang et al., 2016). It is overexpressed in diversity of malignant tumors (Shvartsur and Bonavida, 2015) and is coded by the tumor associated calcium signal transducer gene located on p32 of chromosome 1. It has a notable role in the regulation of intracellular calcium concentration.
Few studies were performed to assess TROP-2 diagnostic value in PTC and no studies conducted to evaluate its diagnostic role in the newly adopted borderline category.
The aim of this study is to assess the diagnostic value in the differentiation between benign, borderline and PTC thyroid lesions.
This study included 55 cases of different thyroid lesions which were collected from the Pathology-Faculty of Medicine- Ain Shams University, during the period from 2011-2016. The selected blocks were sectioned 5µm thick sections and immunostained using concentrated Rabbit polyclonal IgG antibody against TROP-2 from Genetex Company, USA. Evaluation of immunostaining results followed by statistical analysis was carried out.
We found that TROP-2 is expressed in 86.67% of PTC compared to only 6.25% of the benign thyroid lesions. As regard the FVPTC, TROP-2 was expressed in 70% of the cases. We also reported TROP-2 immunoreactivity in 55.6% of the borderline thyroid lesions.
The immunoreactivity of TROP-2 was significantly different among different thyroid lesions (P <0.0001). TROP2 immunoreactivity was higher in the PTC group compared to benign thyroid lesions group (P <0.0001). There was a significant difference in TROP-2 expression between FVPTC compared to the benign follicular patterned lesions including hyperplastic nodules and follicular adenoma (P = 0.019). However, there was no significant difference in TROP-2 immunoreactivity between FVPTC and borderline thyroid lesions group (P = 0.649). The immunoreactivity of TROP-2 was significantly higher in the borderline thyroid lesion group compared to benign thyroid lesions group (P = 0.01).
We reported high sensitivity and specificity of TROP-2 in the diagnosis of PTC; 86.67% and 93.75% respectively with overall diagnostic accuracy 89.13%. TROP-2 expression in FVPTC can differentiate it from benign follicular nodules with 70% sensitivity, 90% specificity and diagnostic accuracy 80%.
Also the diagnostic value of TROP-2 in the newly implemented borderline category can’t be undervalued as it can differentiate this category from benign lesions with 55.6% sensitivity, 93.75% specificity and diagnostic accuracy 80%.
Furthermore, TROP-2 expression in the borderline category stratifies this category into low risk group which is TROP-2 negative and high risk group which is TROP-2 positive. The risk stratification needs further follow up studies to be confirmed. Close strict clinical follow up for this category especially TROP-2 positive cases should be performed to pick up any early invasive features and malignant transformation.
TROP-2 is valuable marker that can aid the diagnosis of PTC in the indefinite histopathological cases, specifically the classic variant, and differentiate it from other non-PTC lesions with high sensitivity and specificity