Morphology and metastatic potential of papillary thyroid carcinoma
A. Abrosimov, S. Kozhushnaya & E. Lushnikov
Papillary thyroid carcinoma (PTC) is a malignant tumor of follicular cell origin that is characterized by a broad diversity of morphological features. There are 15 different histological types of PTC in the recent edition of WHO classification. Morphology of PTC is important to estimate a metastatic potential of tumor and to make an accurate prognosis of clinical behaviour.
Objective of the work is to study a relationship between frequency of regional metastasis and morphological variant of PTC, size of primary tumor and breadth of invasiveness.
Materials and methods. Histological sections, paraffin blocks and pathology reports of 325 PTCs in 322 patients (60 males and 262 females aged from 10 to 76 years) were studied. Histological typing was made in accordance with WHO classification (2004). Conventional type of PTC was subclassified into variants with and without focal tall cell component.
Results. Conventional type of PTC (86 tumors) is diagnosed in 85 patients, follicular variant - in 11, solid - in 26, encapsulated - in 7, oxyphilic type - in 4, Warthin-like - in 9, tall and columnar cell variant - in 7 cases. Conventional type of microPTC (122 tumors) is revealed in 120 patients, microcarcinoma with follicular architecture - in 25, with solid architecture - in 28 cases. Regional metastases are revealed with high frequency in PTCs of oxyphilic type (100%), tall and columnar cell (71%) and solid variants (62%); with moderate rate in PTCs of conventional (49%), follicular (45%), Warthin-like variants (44%) and microPTC of conventional type (32%); with low frequency in microPTC of solid-follicular type (11%). PTCs with regional metastasis have biger size of primary tumor and higher frequency of vascular invasion than PTCs without metastasis. MicroPTCs of conventional type with focal tall cell component are characterized by higher frequency of regional metastasis (50%) in comparison with microPTCs in patients of the same age, gender and tumor invasiveness without focal tall cell component (24%).
Conclusions. Frequency of regional metastasis is varied in different histotypes of PTC and is dependent on the size of primary tumor and vascular invasiveness. Papillary microcarcinomas of conventional type with focal tall cell component have higher metastatic potential in comparison with microcarcinomas without tall cell component in patients of the same age, gender, tumor size and invasiveness.
Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.
Funding: This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector