Objective: Metastatic colorectal cancer (mCRC) patients with BRAF mutation V600E present poor overall survival (OS). RAC1b, a RAC1 spliced variant, is overexpressed in CRC and impairs apoptosis by activation of nuclear-factor-KB. We evaluated if RAC1b was an independent prognostic factor in mCRC. Method: We examined BRAF (V600E) mutational status, RAC1b by immunohistochemistry, RAC1b/RAC1 expression ratio by mRNA RT-PCR, and mismatch repair (MRR) deficiency by microsatellite instability (MSI) analysis, in 186 mCRC patients treated in firstline therapy with FOLFOX or CAPOX from three Spanish institutions. We assessed whether these biomarkers were independently predictive of progression free survival (PFS) or OS. Results: 7 % CRC had BRAF mutations, 5 % MSI-H, 20 % high RAC1b/RAC1 ratio, and 25 % RAC1b protein overexpression. Five of 11 CRC (46 %) with BRAF mutations had high RAC1b/RAC1 ratio/protein vs 25/144 (18 %) without BRAF mutation (p=0.036). All BRAF mutated or RAC1b/RAC1 high were MSS. Low RAC1b/RAC1 ratio and BRAF WT had higher response rate (68 % vs 43 %; p= 0.035). Multivariate regression analysis identified ECOG PS as a significant variable for PFS and LDH levels, PS and high RAC1b/RAC1 ratio for OS. Conclusion: High RAC1b/RAC1 expression ratio or immunoexpression constitutes a marker of poor OS and a potential marker of acquired chemo-resistance in mCRC treated with oxaliplatin-based therapy. Objective: Annually more than 120.000 new cases of papillary thyroid cancer, that is 1 % of malignant tumors, are registered all over the world. Method: There are clinical and morphologiсal methods: immunohistochemistry (MMP-2, MMP-9, TIMP-1, TIMP-2), light, transmission, electron, probe and scanning microscopy with the trace element analysis. It was studied 1541 cases of thyroid cancer since. Results: At the papillary thyroid cancer progression matrix metalloprotease and specific tissue inhibitors of metalloprotease (TIMP-2) increased in the cytoplasm of tumor cells, but the concentration of TIMP-1 decreased. Tumors with low degree of ultrastructural differentiation were presented by cells with electron-dense dark cytoplasm and cells with poor cytoplasm organelles and differently formed nucleus with numerous deep invaginations. High level of some matrix metalloproteaseexpression (ММР-9) and low level of TIMP expression (ТIMP-1) were observed in current cases more (45 % and 58 % respectively), than at more differential papillary thyroid cancer (23 % and 37 %). At performance of atomic force microscopy it was shown that connection between cells had become weak at the decreasing of malignancy degree. It was revealed the significant increasing of oxygen, magnium, potassium, calcium in tumor nodes. Conclusion: Conducted comlex morpho-chemistry analysis display diagnostic patterns of papillary thyroid cancer. Objective: Cytological features of BTN-PH, sometimes interpreted as papillary carcinoma (PC) on fine-needle aspiration biopsies (FNAB), have not been studied extensively. Method: Available material from 48 BTN-PH was reviewed retrospectively and compared with 15 PCs. Results: FNAB diagnoses were: non-diagnostic (n=1), benign (n=18), AUS/FLUS (n=10), suspicious for follicular neoplasm (n=4), suspicious for malignancy (S-PC) (n=13), and malignant (P-PC) (n=2). The extent of papillary hyperplasia on histology was higher in S-PC/P-PC diagnostic categories (50 %; P=0.019; range: 5-90 %). On cytology, papillary structures, present in 53 % of BPN-PH cases, were more frequent and numerous in the S-PC/P-PC group (89 %; P= 0.0093). Focal nuclear atypia was seen in all S-PC/P-PC cases, including rare grooves (87.5 %), enlargement/crowding (75 %), chromatin clearing/rare pseudoinclusions (25 %), but were less than in PCs (P<0.0001). Nuclei were smaller in BTN-PH than in PCs (mean diameter/range (μm): 8.2/6-12 vs 14.2/7-26; P=0.0001). All BTN-PH tested (n=9) were immunonegative for HBME-1, galectin-3, and keratin-19. Conclusion: BTN-PH diagnosed as S-PC/P-PC often show papillary structures and focal nuclear features of PC but they are significantly less than in classical PCs, stressing the need to apply strict criteria for PC diagnosis.