DIAGNOSIS OF GERM CELL TUMORS OF EXTRAGONADAL LOCALIZATION IN TERMS OF ALGORITHMS FOR DETECTING METASTASIS OF CARCINOMAS OF UNKNOWN PRIMARY LOCALIZATION

Abstract

The analysis of cases of extragonadal teratomas makes it clear that tumours derived from germ cells and mainly characteristic of adult gonads can also occur in other areas, such as the anterior mediastinum (thymus) and midline brain (germinomas of the epiphysis and the area above the Turkish saddle), that requires differential diagnosis with metastases of carcinomas of other origin. Accurate diagnosis of estrogenic germ-cell tumours by only routine staining with haematoxylin-eosin requires high expertise and experience due to their non-specific clinical symptoms and variability of morphological characteristics. Tumour morphologists consider that immunohistochemical investigation plays an important role in accurate histological diagnosis of these tumours. The goal of this study is to explore the expression features of immunohistochemical markers and morphometric parameters of the area, perimeter and "roundness" of the nuclei in various types of extragonadal germ-cell tumours compared to similar primary ovarian / testicular tumours in order to improve diagnostic algorithms. A study was conducted on biopsy or postoperative samples taken from 8 patients (group 1) with extragonadal germ-cell tumours and from 16 patients with primary germ cell tumours of testicles / ovaries (group 2). The diagnoses were confirmed by immunohistochemical investigation on the basis of the pathologic department of the “Pharmacy of Medical Academy” Diagnostic Centre for 2015 to 2018. PLAP and CD117 had the highest percentage of expression in seminomas and gerninomas of both studied groups; morphological parameters were 3-fold higher in area and ̴2-fold higher around the perimeter then the values of normal lymphocytes (p<0.05). Expression of markers CD30, EMA and CK AE1/3 was diagnostically significant in samples of embryonic carcinoma, and morphological parameters ̴were ̴ 2.1 times higher in area and ̴ 1.7 along the perimeter that exceeded the values of normal lymphocytes (p<0.05). αFP-positive staining was indicative of yolk sac tumours, which morphological parameters were more than ̴ 1.7 times higher in the area and ̴ 1.5 times higher along the perimeter compared with the normal lymphocytes (p<0.05). Taking into account the variability of morphological characteristics and the possibility of extragonadal location of tumours derived from germ cells, immunohistochemical research supported by morphometry is an important tool in the differential diagnosis of carcinomas of unknown primary localization.