Aim: Pathohistological diagnostics (PD) of the Yolc Sac tumor (YST) of primary mediastinal localization. Introduction: YST are malignant germ cell tumors of primitive endodermal gonadal differentiation. In 1% -5% of cases their localization is extragonadal, including mediastinal in 50% -70% published cases. Case report: A 30-year-old man was admitted to the Thoracic Surgery Clinic for diagnosis and treatment of mediastinal tumor with lungs and liver metastases. Laboratory analyzes revealed high elevations in serum alpha-fetoprotein (AFP), in addition moderate elevation of beta-chorionic gonadotropin (ß-HCG). No pathological changes in testis and retroperitoneum have been found. An open biopsy of the mediastinal change was made for PD. Histologically, tumor tissue showed a significant degree of necrosis. There were reticular, microcystic and pseudopapillary forms of neoplastic cell growth, surrounded by myxomatosis stroma. Tumor cells cytoplasm was scarce and vacuolated with high nuclear polymorphism and hyperchromasia. Positive immunohistochemical (IMH) reaction was obtained for panCK, AFP, PLAP. Immunoreactivity for TTF-1 was found in about 50% of tumor cells, as well as the focal reaction for ß-HCG in rare multinuclear cells. Reactions for D2-40, CD5, CK-7, CK-20, p63, CD117, CD30, napsin A and calretinin were negative. Conclusion: The results of our analysis showed the expression of divergent endodermal linear markers in the mediastinal YST, especially TTF-1 expression. The diagnosis of YST in small biopsies can be difficult and requires using of a wide range of IMH markers in order to closer the differentiation of primary tumor localization and the application of appropriate chemotherapy

Aim: Determining the immunohistochemical characteristic of parathyroid glands (PG) proliferative activity in patients with primary and secondary hyperparathyroidism (HPT) using cell cycle and proliferation immunohistochemical markers, Ki -67 and PCNA. Introduction: A few studies results have shown A few studies results have shown significant detection of Ki-67 in hyperplasia due to secondary hyperparathyroidism (sHPT), whereas it s demonstrated only in adenomas in primary HPT (pHPT). The highest PCNA expression is detected in hyperplastic PG in sHPT and in adenoma in pHTP, but in pHTP hyperplasia it s extremely low. Material and Methods: We analyzed the surgically removed PG of 96 patients with HPT. In POSTER SESIJA 64 MATERIA MEDICA • Vol. 34 • Issue 1, suplement 1 • april 2018. addition to standard histopathological parameters the results of immunohistochemical reaction of Ki-67 and PCNA in 23 normal, 73 hyperplastic PG and 23 adenoma were analyzed. Results: 41 (42.7%) patients had pHPT, and 55 (57.3%) sHPT. Within pHPT adenoma was diagnosed in 23 (56.1%) patients and hyperplasia in 18 (43.9%). Detection of PCNA was 94.4% in pHPT hyperplasia, 91% in sHPT hyperplasia, and 83% in adenoma. 22 (98%) of the normal PG didn t have PCNA expression. The expression of Ki-67 was found in 13 (56.5%) adenomas and in 11 (18.3%) nodular hyperplasia. The high statistical significance for Ki-67 (p <0.0001) was found between adenoma and pHPT and sHPT. Conclusion: The results of our analysis showed high Ki-67 and PCNA expression in parathyroid adenomas. Increased Ki-67 expression corresponds with increased cellular proliferation and contributes to tumorigenesis in many organs, but doesn t distinguish accurately benign from malignant PG tumors.