Lung cancers are the most common cause of morbidity and mortality from malignant tumors in the World. The neodjuvant therapy in patients with locally advanced (IIIA-IIIB) lung cancer and affected N2 lymph nodes is one of the modes of multimodal treatment of patients with non-small cell lung cancer (NSCLC) in order to improve the outcome of their treatment. This involves converting patients from a higher to a lower stage of the disease - “downstaging”. There has been no significant connection between some forms of tumor response and types of therapy. Given the importance of complete pathological responses and tumor regression in the prediction of treatment outcomes, finding this relationship is of importance for the design of future neoadjuvant trails. In determining the histological tumor regression is very important measurement of area of residual tumor (ART). As the size of the tumor is one of the prognostic factors in patients with NSCLC who did not receive neoadjuvant therapy so the measurement of ART, as opposed to the macroscopic size of the tumor, one of the prognostic factors in patients with NSCLC, who had received neoadjuvant therapy. The ultimate goal of neoadjuvant therapy should be resectability and “downstaging” that could provide overall oncology benefit in specific clinical situations. The main objectives of this research were: to objectively estimate the size of ART in tumor tissue of lung and lymph nodes; to estimate the relation between the surface of ART with the size of the tumor on postoperative surgical material after neoadjuvant therapy; to analyze and estimate the relation between histomorphological parameters in tumor regression induced by neoadjuvant therapy and spontaneous tumor regression in tumors of the lung and lymph nodes in the postoperative surgical material and depending on the histological type of cancer; to estimate the relation between clinical response to neoadjuvant therapy according to criteria of the World Health Organization and histological parameters in lung tumors and lymph nodes in the postoperative surgical material after neoadjuvant therapy; to estimate the correlation of the pathological ypTN with clinical ycTN stage of the disease and the degree of tumor regression induced by neoadjuvant therapy and pathological ypTN and estimation of the relation between clinical and pathological involvement of N2 lymph nodes after neoadjuvant therapy. Measurement of the total size of the preserved ART is the most important objective parameter in the assessment of the grade of tumor regression. Size of residual tumor did not correlate with the size of the tumor after neoadjuvant therapy. There was a significant difference in the histological picture of tumor regression induced by neoadjuvant therapy and spontaneous tumor regression. There was no significant difference between the histologic type of tumor and histological tumor regression. There is no significant correlation between clinical response and the grade of tumor regression after neoadjuvant therapy. There is no correlation between clinical and pathological staging of the diseaSPECIAL SESSION: DEPARTMENT OF PATHOLOGY, MEDICAL FACULTY, UNIVERSITY NOVI SAD, SERBIA 34 MATERIA MEDICA • Vol. 34 • Issue 1, suplement 1 • april 2018. se after neoadjuvant therapy. There is no correlation between the grade of tumor regression induced by neoadjuvant therapy and ypTN stage of the disease. There is no correlation between the clinical and the pathological involvement of the N2 lymph nodes to neoadjuvant therapy. The grade of tumor regression and measurement ART after neoadjuvant therapy determined by histopathological analysis of the resected tumor is the most objective criterion for evaluation of chemotherapeutic response and prediction of treatment outcome in patients.

Aim: To determine the degree of correlation between TTF-1 (+) expression and EGFR mutation status in lung adenocarcinoma. Introduction: Adenocarcinoma of the lung is mainly diagnosed based on standard morphological criteria. The thyroid gland transcription factor (TTF-1) is currently the most commonly used immunohistochemical marker in the differentiation of invasive adenocarcinoma of the lung from another primary and metastatic carcinoma, has a prognostic significance and is a predictor of the EGFR mutation status. Material and Methods: This retrospective study enrolled 60 patients with histologically confirmed primary lung adenocarcinoma who underwent lung cancer surgery at Institute for lung disease Vojvodina between 2010 and 2015. Tumor specimens of these patients were investigated for TTF-1 expression and mutations in EGFR using immunohistochemistry and PCR analysis. Statistical analysis is in statistic software Statistica 12. Results: The study included 35 men and 25 women, with an average age of 61.8 ą 8.08 years. Of the 60 cases, TTF-1 ( ) expression was recorded in 52 (87%) (p <0.001), the statistical difference is not significant when comparing smoking habitsby gender, and tumor size among them. EGFR ( ) mutation status was found in 3/60 (5%) cases [egzon 21 (2) and exon 20 (1)], of which TTF-1 (+) expression was in two cases. Conclusion: There is a statistically significant difference between the TTF-1 (-) and TTF-1 (+) adenocarcinoma and a high degree of correlation between EGFR mutation status and TTF-1 (+) expression.

Aim: Analysis of two cases of IPA with an emphasis on the radiological and pathohistological findings of this entity. Introduction: Aspergillus spp. can cause a wide range of lung diseases, depending on the current state of immunity and the existing pulmonary diseases. Invasive pulmonary aspergillosis (IPA) is severe form of pulmonary mycosis, with the appearance of granulomatous inflammation with the development of necrosis and suppuration, as well as the invasion of hyphae into pulmonary parenchyma and the blood vessels and spreading the disease out of the lungs. Material and Methods: In the five-year period, two cases of IPA were diagnosed at the Institute of Pulmonary Diseases of Vojvodina. Material for pathohistological analysis, obtained by surgical method and on autopsy, was stained with standard H E staining, as well as with special staining methods: PAS and Grocott. Results: Patients were 67 and 48 years old and both were treated for acute lymphoblastic leukemia. They were admitted to our hospital in respiratory insufficiency and severe neutropenia with a radiologically diagnosed IPA based on HRCT finding of “halo sign”. This sign pathohistologically corresponds to foci of necrosis of lung parenchyma surrounded with the zone of hemorrhage. In addition to these foci of necrosis, in the wall and lumen of blood vessels, numerous septate hyphae with dichotomous branching at 45° were found. Conclusion: Although the pathohistological diagnosis is golden standard for diagnosis of IPA, given the invasiveness of the techniques for obtaining material for analysis, diagnosis can be made based on HRCT finding of “halo sign”.

Aim: The aim of this case was a correct diagnosis of mediastinal tumor in a 41-years old female patient. Introduction: The rarity of primary extraneural ependymomas, its great variations in morphology and rare occurrence of metastasis, increase chances of misdiagnosis. Case report: Macroscopic examination of received specimen was performed, followed by histological and immunohistochemical analysis of the tissue samples. In presented case, onset of the disease was 14 years ago, when after right salpingo-oophorectomy, patient was diagnosed with malignant mesothelioma. In following years patient had multiple and extensive surgical procedures, resulting in different patohistological diagnosis, and after seven years, a diagnosis of extraneural ependymoma was established. Later on, patient was surgically treated in several medical centers across the region, again with different patohistological diagnosis. At present, tumor metastasized to mediastinum, presenting as grey to brown, multicystic formation, with cysts filed with clear serous fluid or red-brown hemorrhagic fluid. Inner surface of the cysts had smooth to partly papillary appearance. Tumor cells exhibited several architectural paterns (solid, pseudorosette or rosette formations, papillary and pseudopapilary structures), and immunophenotype specific for extraneural ependymoma (GFAP, ER, PR positive, calretinin, WT-1, S100, synaptophysin, chromogranin, CK7 and pan-cytokeratin negative). Conclusion: This case demonstrates an important principle in tumor pathology. Neoplasms may occur in unusual and unexpected primary and metastatic sites. Pathologists need to be familiar with histologic features of a wide range of neoplasms and not just the appearance of neoplasms within their own limited subspecialty area.