 Histopathological and immunohistochemical characteristics of adult renal tumors: a five-year retrospective study in Mureş County, Romania 
Renal tumors account for approximately 3% of all adult neoplasms . The occurrence is higher in countries with high incomes compared to middle- and low-income ones, presently standing as the seventh most prevalent cancer among men and the tenth most prevalent among women, with an increasing prevalence. It is commonly seen in patients in their sixth and seventh decade of life, with a median age of 64 years . Apart from smoking, obesity, and hypertension, genetic factors have been linked in the development of renal cell carcinoma (RCC). Therefore, RCC can occur as a sporadic form (~96%) or can be associated with familial syndromes [4% – a small percentage being associated with von Hippel–Lindau (VHL) disease] . The 2022 World Health Organization (WHO) Classification of renal tumors includes a wide spectrum of tumors ranging from benign to malignant, with several new entities defined on cytological, architectural, immunohistochemical (IHC), and cytogenetic characteristics. Clear cell renal cell carcinoma (CCRCC) still remains the most frequent histopathological subtype, followed by papillary renal cell carcinoma (PRCC), and chromophobe renal cell carcinoma (ChRCC), while renal oncocytoma (RO) is the most common benign tumor . Histology currently represents the “gold standard” of the diagnosis  not only for establishing the tumor type, but particularly for identifying those factors which are directly correlated with the severity and prognosis of RCC : tumor stage and grade, presence of sarcomatoid/rhabdoid features and necrosis. Immunohistochemistry is an additional tool for establishing the histological subtype in cases where the histology is not conclusive . Unfortunately, most of the cases are discovered incidentally, in advanced stages, following ultrasonography (US), magnetic resonance imaging (MRI) or computed tomography (CT) examination for various medical conditions . Despite the progress made in diagnosing and treating RCC over the past 20 years, it remains the deadliest urological cancer, with a mortality rate of approximately 40% . Diagnosis in early stages would be an important step in order to improve the patients’ chance of survival . Aim The aim of our study was to assess the prevalence trend, as well as demographic and pathological characteristics of renal tumors over the last five years in Mureş County Clinical Hospital, Romania, and border areas.   The aim of our study was to assess the prevalence trend, as well as demographic and pathological characteristics of renal tumors over the last five years in Mureş County Clinical Hospital, Romania, and border areas.   Case selection We performed a retrospective study between January 2018 to December 2022 at the Pathology Department of Mureş County Clinical Hospital, including all patients who underwent a total or partial nephrectomy for renal tumor. All data were processed with the informed consent of the patients. This study was approved by the Ethics Committee of Mureş County Clinical Hospital (Approval No. 6817/2022). Clinical and pathological data Patient demographics (age and gender group) were collected from the Medical Records of Urology and Pathology Departments, respectively. All cases were reviewed by two pathologists specialized in uropathology (AB, AL). The histopathological features [tumor subtype, tumor stage, vascular invasion, necrosis, lymph node metastasis (LNM) and distant metastasis, when it was included in the resection specimen] were re-assessed based on Hematoxylin–Eosin (HE)-stained slides according to latest 2022 WHO Classification of Urinary and Male Genital Tumours (5th edition). We considered CCRCC as a tumor with optically clear cytoplasm cells, arranged in nests, tubes, or alveoli with a distinctive vascular pattern as a diagnostic indicator to distinguish it from other tumors . All cases of papillary carcinoma, regardless of whether they were type 1 or 2, were included in a single category according to the latest 2022 WHO Classification of Urinary and Male Genital Tumours (5th edition). Thus, a diagnosis of PRCC was made when the tumor had papillary or tubulo-papillary architecture with foamy macrophages in the axis of the papillae, lined by cuboidal cells with pale basophilic cytoplasm and uniform nuclei. Other morphological patterns included a solid growth, or thinly branching papillae lined by a pseudostratified layer of tumor cells, with abundant eosinophilic cytoplasm and nuclear atypia . All tumors with a solid architecture and with two types of cells (one with finely reticulated and translucent appearance, of the cytoplasm, often exhibiting a clear to foamy aspect and another type with densely eosinophilic and granular cytoplasm) were diagnosed as ChRCC. The nuclei were hyperchromatic, with irregular and wrinkled (raisinoid) appearance, with the presence of perinuclear haloes as a distinguishing characteristic, frequently with binucleation . Sarcomatoid and rhabdoid differentiation were assessed in all histological subtypes. Sarcomatoid differentiation was considered when spindle cells organized in sheets and fascicles with cellular atypia and high nuclear pleomorphism were identified. Rhabdoid differentiation was considered when either cohesive groups of cells or individual round to polygonal cells with a loose arrangement and eosinophilic inclusions within their globular cytoplasm and large, irregular nuclei situated off-center were present . A diagnosis of RO was established when the tumor was well-circumscribed with a solid, microcystic, macrocystic or tubular architecture, and a characteristic central scar. The tumor cells were round to polygonal, displaying densely granular eosinophilic cytoplasm with round, uniform nuclei and a small nucleolus at the center, embedded in myxoid or hypocellular hyalinized stroma . Other rare histological subtypes were defined by a set of histopathological criteria in accordance with latest 2022 WHO Classification of Urinary and Male Genital Tumours (5th edition). Tumors included in the study were graded according to Fuhrman’s and WHO/International Society of Urological Pathology (ISUP) grading systems. All tumors graded before 2019 according to Fuhrman’s grading system were re-assessed in line with the WHO/ISUP grading system (4th edition), as follows: grade 1 – absent or not easily noticeable nucleoli at high magnification (40×); grade 2 – not prominently visible nucleoli at a low magnification (10×), but visible, eosinophilic nucleoli at high magnification (40×); grade 3 – clearly visible, reddish nucleoli at low magnification (10×); grade 4 – nuclei with extreme variation in shape, presence of multinucleated cells, displaying features of rhabdoid and/or sarcomatoid differentiation. The pathological stage was assessed according to the latest 2022 WHO Classification of Urinary and Male Genital Tumours (5th edition) . In cases with misleading morphology, a panel of five antibodies was used: anti-paired-box 8 (PAX8; mouse monoclonal primary antibody, clone MRQ-50, Cat# 760-4618), anti-cluster of differentiation 10 (CD10; rabbit monoclonal antibody, clone SP-67, Cat# 790-4506), anti-alpha-methylacyl-coenzyme A (CoA) racemase (AMACR; mouse monoclonal antibody, clone SP116, Cat# 760-501), anti-cytokeratin 7 (CK7; rabbit monoclonal primary antibody, clone SP52, Cat# 790-4462), anti-cluster of differentiation 117 [CD117 (c-Kit); monoclonal primary antibody, clone 9.7, Cat# 790-2951]. Staining procedures were performed on the Ventana BenchMark ULTRA (Ventana Medical Systems, Inc., Tucson, AZ, USA) automated stainer following the manufacturer’s protocols. The IHC reactions were considered positive as follows: nuclear staining for PAX8, membranous staining for CD10 and CD117, cytoplasmic staining for AMACR, cytoplasmic and membranous staining for CK7. Statistical analysis Statistical analysis was performed using Microsoft Excel and Statistical Package for the Social Sciences (SPSS; IBM v29.0) program for macOS. Descriptive statistics were applied to analyze the data.   We performed a retrospective study between January 2018 to December 2022 at the Pathology Department of Mureş County Clinical Hospital, including all patients who underwent a total or partial nephrectomy for renal tumor. All data were processed with the informed consent of the patients. This study was approved by the Ethics Committee of Mureş County Clinical Hospital (Approval No. 6817/2022).   Patient demographics (age and gender group) were collected from the Medical Records of Urology and Pathology Departments, respectively. All cases were reviewed by two pathologists specialized in uropathology (AB, AL). The histopathological features [tumor subtype, tumor stage, vascular invasion, necrosis, lymph node metastasis (LNM) and distant metastasis, when it was included in the resection specimen] were re-assessed based on Hematoxylin–Eosin (HE)-stained slides according to latest 2022 WHO Classification of Urinary and Male Genital Tumours (5th edition). We considered CCRCC as a tumor with optically clear cytoplasm cells, arranged in nests, tubes, or alveoli with a distinctive vascular pattern as a diagnostic indicator to distinguish it from other tumors . All cases of papillary carcinoma, regardless of whether they were type 1 or 2, were included in a single category according to the latest 2022 WHO Classification of Urinary and Male Genital Tumours (5th edition). Thus, a diagnosis of PRCC was made when the tumor had papillary or tubulo-papillary architecture with foamy macrophages in the axis of the papillae, lined by cuboidal cells with pale basophilic cytoplasm and uniform nuclei. Other morphological patterns included a solid growth, or thinly branching papillae lined by a pseudostratified layer of tumor cells, with abundant eosinophilic cytoplasm and nuclear atypia . All tumors with a solid architecture and with two types of cells (one with finely reticulated and translucent appearance, of the cytoplasm, often exhibiting a clear to foamy aspect and another type with densely eosinophilic and granular cytoplasm) were diagnosed as ChRCC. The nuclei were hyperchromatic, with irregular and wrinkled (raisinoid) appearance, with the presence of perinuclear haloes as a distinguishing characteristic, frequently with binucleation . Sarcomatoid and rhabdoid differentiation were assessed in all histological subtypes. Sarcomatoid differentiation was considered when spindle cells organized in sheets and fascicles with cellular atypia and high nuclear pleomorphism were identified. Rhabdoid differentiation was considered when either cohesive groups of cells or individual round to polygonal cells with a loose arrangement and eosinophilic inclusions within their globular cytoplasm and large, irregular nuclei situated off-center were present . A diagnosis of RO was established when the tumor was well-circumscribed with a solid, microcystic, macrocystic or tubular architecture, and a characteristic central scar. The tumor cells were round to polygonal, displaying densely granular eosinophilic cytoplasm with round, uniform nuclei and a small nucleolus at the center, embedded in myxoid or hypocellular hyalinized stroma . Other rare histological subtypes were defined by a set of histopathological criteria in accordance with latest 2022 WHO Classification of Urinary and Male Genital Tumours (5th edition). Tumors included in the study were graded according to Fuhrman’s and WHO/International Society of Urological Pathology (ISUP) grading systems. All tumors graded before 2019 according to Fuhrman’s grading system were re-assessed in line with the WHO/ISUP grading system (4th edition), as follows: grade 1 – absent or not easily noticeable nucleoli at high magnification (40×); grade 2 – not prominently visible nucleoli at a low magnification (10×), but visible, eosinophilic nucleoli at high magnification (40×); grade 3 – clearly visible, reddish nucleoli at low magnification (10×); grade 4 – nuclei with extreme variation in shape, presence of multinucleated cells, displaying features of rhabdoid and/or sarcomatoid differentiation. The pathological stage was assessed according to the latest 2022 WHO Classification of Urinary and Male Genital Tumours (5th edition) . In cases with misleading morphology, a panel of five antibodies was used: anti-paired-box 8 (PAX8; mouse monoclonal primary antibody, clone MRQ-50, Cat# 760-4618), anti-cluster of differentiation 10 (CD10; rabbit monoclonal antibody, clone SP-67, Cat# 790-4506), anti-alpha-methylacyl-coenzyme A (CoA) racemase (AMACR; mouse monoclonal antibody, clone SP116, Cat# 760-501), anti-cytokeratin 7 (CK7; rabbit monoclonal primary antibody, clone SP52, Cat# 790-4462), anti-cluster of differentiation 117 [CD117 (c-Kit); monoclonal primary antibody, clone 9.7, Cat# 790-2951]. Staining procedures were performed on the Ventana BenchMark ULTRA (Ventana Medical Systems, Inc., Tucson, AZ, USA) automated stainer following the manufacturer’s protocols. The IHC reactions were considered positive as follows: nuclear staining for PAX8, membranous staining for CD10 and CD117, cytoplasmic staining for AMACR, cytoplasmic and membranous staining for CK7.   Statistical analysis was performed using Microsoft Excel and Statistical Package for the Social Sciences (SPSS; IBM v29.0) program for macOS. Descriptive statistics were applied to analyze the data.   Two hundred twenty cases of total/partial nephrectomies were included in our study. The distribution of cases during the study period is shown in Figure . Notably, there was a decrease of cases during the initial phase of the coronavirus disease 2019 (COVID-19) pandemic (2020), followed by a significant increase in 2021. Table (gender, site of the tumor, histological subtype) summarizes the demographic and pathological data for the study cases. Among the 220 patients included in this study, the majority (n=138, 62.7%) were men, less than half (n=82, 37.2%) being women. Over half of the patients (n=146, 63.63%) were ≥60 years old, 32.27% (n=71) were between 40–59 years old, while only 1.36% (n=3) were less than 40 years old. The mean age was 62.72 years (range: 33–84 years). We found a predominance of right kidney tumor masses, with 52.2% (n=115), compared to 47.7% in the left kidney. As shown in Table , the most common histological subtype was CCRCC (n=181, 82.27%), some of the cases with sarcomatoid/rhabdoid differentiation (n=24, 10.9%) (Figures , ), followed by RO (n=16, 7.27%), PRCC (n=15, 6.81%) (Figure ), ChRCC (n=6, 2.72%) (Figure ), and rare subtypes [Xp11.2 translocation RCC, n=1, 0.45%; thyroid-like follicular carcinoma (TLFC), n=1, 0.45%]. IHC was performed for cases with atypical or overlapping morphology (n=41, 18.63%). IHC staining with PAX8, CD10 and AMACR confirmed the CCRCC diagnosis in 18 out of 181 cases, while AMACR and CK7 were performed for PRCC in 10 out of 15 cases. CD117 and CK7 were used to differentiate ChRCC from RO [n=6 (2.7%) and n=16 (7.2%), respectively]. Table documents the demographic and pathological characteristics of the renal malignant tumors according to the histological subtype. We observed a minimal variation in the distribution of cases among different stages of RCC, therefore pT3a was the most frequent stage (n=64, 29.09%), followed closely by pT1b (n=58, 26.4%) and pT1a (n=57, 25.9%), while the least common was pT4 stage (n=3, 1.36%). We examined each histological subtype according to different pathological characteristics and found that most CCRCC cases were pT1b (n=51, 23.2%), closely followed by pT1a (n=48, 21.8%) and pT3a (n=41, 18.6%). All pT3a cases were accompanied by vascular invasion (n=30, 13.6%), tumor necrosis (n=38, 17.3%), sinus fat invasion (n=20, 9.0%), perinephric fat invasion (n=11, 5.0%) and distant metastasis (n=1, 0.9%), showing a more aggressive behavior. Moreover, CCRCC with sarcomatoid/rhabdoid differentiation was more frequently identified in advanced stages such as pT3a (n=18, 8.2%), all of them associated with LNM, vascular invasion, tumor necrosis, sinus fat invasion and perinephric fat invasion, without distant metastasis. Out of 15 analyzed cases of PRCC, pT1a stage (n=6, 2.7%) was most commonly identified, followed closely by pT3a stage (n=4, 1.8%) associated with LNM, tumor necrosis and vascular invasions, and pT2a stage (n=3, 1.4%) associated with tumor necrosis. ChRCC was one of the least common histological subtypes, identified in pT1b (n=3, 1.4%) and pT2a (n=2, 0.9%) stages, with no LNM, distant metastases or vascular invasions showing a less aggressive profile compared to other types of renal carcinoma. Although sinus fat invasion was observed in 35 cases, primarily of CCRCC with and without sarcomatoid/rhabdoid differentiation (n=32, 91.4%), perinephric fat invasion was noted in 21 (9.54%) cases of CCRCC, including 10 (4.54%) cases with sarcomatoid/rhabdoid features, one (0.45%) case of ChRCC, and one (0.45%) case of Xp11.2 translocation. Necrosis was identified in tumors with a higher stage, over half of them in pT3a and pT4 stages. There were 55 cases of CCRCC of which 17 cases with sarcomatoid/rhabdoid features, five cases of PRCC, one case of ChRCC and one case of Xp11.2 translocation. In terms of distant metastasis, one case of CCRCC had ipsilateral adrenal gland metastasis (found at the time of surgery). Histopathological analysis of the 181 cases of CCRCC and 15 of PRCC showed that that more than half (n=122, 62.24%) of the cases were low-grade tumors (WHO/ISUP grade 2) including pT1b (n=42), pT1a (n=39) and pT3a (n=17) stages for CCRCC and pT1a (n=4), pT2a (n=3) and pT3a (n=2) stages for PRCC, with WHO/ISUP grade 3 as the second most common finding. Most of the high-grade tumors (WHO/ISUP grade 3 and WHO/ISUP grade 4) were observed in a higher stage such as pT3a. All cases with sarcomatoid/rhabdoid features were graded as high-grade tumors (WHO/ISUP grade 4) (Table ).   The results of our study provide a comprehensive overview of the demographic (gender, age) and pathological characteristics (RCC subtypes, tumor stage, vascular invasion, necrosis, LNM and distant metastasis) of renal tumors over a five-year period in our region and border areas. The incidence rates of RCC show notable variations across different regions worldwide. Globally, North America stands out with the highest estimated incidence (12/100 000), indicating cumulative risks of 1.8% for males and 0.9% for females. In Western Europe, the highest incidence rates (9.8%) are for both genders. In contrast, Africa exhibits the lowest incidence and mortality rates, with cumulative risks less than 0.2% for both genders . The impact of COVID-19 has been widely documented in the literature. This epidemiological emergency has led to a decline in clinical and surgical activities, affecting patients’ access to high-quality medical services . In our department, we observed a decrease of renal tumors cases during the initial phase of the COVID-19 pandemic (year 2020), followed by a significant increase in 2021. This trend was also reported by Mariotto et al., with a decrease of cases by 10% in 2020 compared to 2019, due to delays in cancer diagnosis and screening caused by the pandemic. However, they observed, that the incidence rates increased in 2021 by 9.4% compared to 2020, indicating a partial recovery in cancer detection and treatment services . Our study found a male predominance (62.7%) compared to female patients (37.2%), with a male-to-female (M:F) ratio of 1.6:1, similar to the literature where there is described a higher occurrence of renal tumors in males compared to females with a M:F ratio of 1.5:1 . Tang et al. reported in their study that the highest incidence of RCC was found in the sixth or seventh decades of life, with a mean age of 61 years . The mean age in our study was 62.6 years, with more than half of the patients being over 60 years old (range 33–84 years). In a study conducted by Padala et al., there was a higher prevalence of right-sided kidney tumors in 68.6% of cases which corresponds with our results where over half of the cases had right kidney renal tumors . According to the data reported in the literature, the most common histological subtypes of RCC are CCRCC, PRCC and ChRCC. Regarding benign tumors, RO is the most common benign epithelial tumor . In the study reported by Sheenu et al., there was a lower prevalence of RO, with only one (1.9%) case identified . However, the exact percentages can vary across different studies . The findings of this present study aligned with the literature, showing that CCRCC is the most common histological subtype (82.3%), with a significant number of cases with sarcomatoid/rhabdoid features (13.3%), followed by PRCC (6.8%), ChRCC (2.7%) and other rare subtypes [Xp11.2 translocation RCC (0.5%) and TLFC of the kidney (TLFC-K) (0.5%)]. RO accounted for only 7.2% of our cases. Mohamed et al.  reported frequencies of 67.8% for CCRCC, 16.6% for PRCC, and 7.1% for ChRCC, respectively, while Ali et al.  found 71.1% for CCRCC, 13.6% for PRCC, and 11% for ChRCC. These findings underscore a lower prevalence of the chromophobe subtype and the highest prevalence of the clear cell subtype. In rare cases, morphology and immunohistochemistry are not specific and molecular biology can help in establishing the histological subtype. In one case of CCRCC, although the microscopic appearance (tubular, microcystic and focally papillary architecture) and an atypical IHC profile (CK7+, CD10–) were not specific for CCRCC, the molecular study that was conducted revealed a VHL gene mutation. These findings underscore that CCRCC can have an unusual microscopic appearance. Ancillary tests are essential for tumors with misleading morphology, because each subtype has a different outcome. In one case, based on a unique histological pattern, exhibiting a combination of clear cells and papillary architecture a suspicion of RCC with Xp11.2 translocation was raised, and the case was referred to a specialized center, Hospital Lyon Sud, France. Ancillary advanced tests confirmed the diagnosis. Xp11.2 translocation-associated RCC has a prognosis that is relatively less understood due to the rarity of reported cases of this neoplasm. The final diagnosis requires confirmation of the Xp11.2 translocation through fluorescence in situ hybridization (FISH) . Another rare subtype of RCC was TLFC-K. Due to the rarity of this entity (<50 cases described in the literature), it was removed from the classification of the latest 2022 WHO Classification of Urinary and Male Genital Tumours (5th edition) . In a study performed by Kuthi et al., the WHO/ISUP grading system for CCRCC indicated that most of the cases were low-grade tumors classified as WHO/ISUP grade 2 (n=364, 47.02%) and WHO/ISUP grade 1 (n=157, 20.28%) . These findings are similar to our results, where the majority of cases were classified as WHO/ISUP grade 2 (n=112, 61.87%). In contrary, WHO/ISUP grade 3 (n=38, 21%) was the second most common finding in our CCRCC cases. Khor et al. showed no significant difference in outcomes between grades 1, 2, and 3, but the difference was significant for grade 4, with a poorer prognosis . In a study conducted by Qian et al., the WHO/ISUP grading system for PRCC indicated that 56 (64.4%) individuals were classified as WHO/ISUP grade 1, 17 (19.5%) as WHO/ISUP grade 2, seven (8.05%) as WHO/ISUP grade 3, and seven (8.05%) as WHO/ISUP grade 4 . In our study, the patients were classified mostly as WHO/ISUP grade 2 (n=10, 66.7%) and WHO/ISUP grade 3 (n=5, 33.3%). Regarding the tumor stage, in Mohamed et al. study, tumor pT2 stage was observed in 50% of the patients, while pT1 stage accounted for 21.4%, pT4 stage for 15.5%, and pT3 stage for 13.1% . These findings are different from the results reported in the majority of other studies . Salako et al. (similar to many other studies in the literature), indicated that most of the cases were in tumor pT3 stage (n=18, 35.3%), followed by pT2 stage (n=14, 27.5%) and pT1 stage (n=10, 19.6%), with the least common pT4 stage (n=9, 17.6%)  and sustain our results. Our study shows that pT3 stage was predominant (66.3%), followed by pT1b stage (28.9%) and pT1a stage (27.9%), with the least common pT4 stage (1.5%). Over 50% of RCCs are detected incidentally due to routine imaging for various medical conditions. Only 30% of RCC patients are diagnosed based on symptoms because small masses often remain asymptomatic. Therefore, up to 20–30% of patients have metastasis at diagnosis, while the classic triad of flank pain, hematuria, and abdominal mass is rare, presenting in only 4–17% of cases. As a result, the tumors are most commonly identified at an advanced stage such as pT3, with a higher nuclear grade as our study also demonstrated (WHO/ISUP grade 3 was the second most common finding). Early diagnosis would significantly improve prognosis . Sinus fat invasion, perinephric fat invasion or invasion into the renal vein are included in pT3a stage, independently of tumor size. In our study, sinus fat invasion was identified in 35 (15.9%) cases: 32 CCRCC cases of which 12 with sarcomatoid/rhabdoid features, two of PRCC and one of Xp11.2 translocation. Twenty-three cases had perinephric fat invasion: 21 cases of CCRCC, one case of ChRCC and one case of Xp11.2 translocation. Some studies, as the one conducted by Stühler et al. revealed that tumors with sinus fat invasion are more aggressive, with a poorer prognosis, compared to those with perinephric fat invasion . These findings emphasize the importance of a well done macroscopy, with multiple sections sampled from the hilum, in order to identify sinus fat invasion. LNM was found in five cases of CCRCC with sarcomatoid features and in two cases of PRCC. All tumors with LNM were of pT3a stage. The presence of LNM is correlated with a higher tumor stage , as our findings also demonstrate. There is also a higher probability of distant metastases for tumors in advanced stages . In our study, we found only one case of CCRCC with distant metastasis. In a comprehensive retrospective study conducted across seven Latin American countries and Spain, it was described that the five-year survival rate for surgically resected RCC reached 86.1%. Several factors identified as significantly influencing survival outcomes leading to a poor prognostic were age, LNM, fat and/or vascular invasion, tumor necrosis, and tumor size exceeding 7 cm . The presence of sarcomatoid/rhabdoid features and vascular invasion were identified as morphological aspects with prognostic value, with the former being associated with a higher grade of the disease and a poor long-term prognosis . In our study, vascular invasion was found in 46 out of 220 (20.9%) cases, most of them in CCRCC (n=43, 19.5%), including some with sarcomatoid/rhabdoid features (n=13, 5.9%), indicating a more aggressive behavior that leads to an unfavorable prognosis. Tumor necrosis is another important histological feature with prognostic value and can be associated with larger tumor size and a higher grade, leading to aggressive tumor behavior. It has been documented in 21–32% of CCRCCs. Several studies have also associated the presence of tumor necrosis with poorer survival outcomes. Researchers found that analyzing both WHO/ISUP grading system and tumor necrosis changed the prognostic compared to WHO/ISUP grading alone. They observed that tumor necrosis significantly influenced prognosis, particularly in WHO/ISUP grade 3 tumors . In our study, tumor necrosis was documented in 28.18% (n=62) of cases, most of them in CCRCC (n=55, 25%) of which 7.7% (n=17) with sarcomatoid/rhabdoid features. Over half of cases were identified in advanced stages such as pT3a, closely followed by pT2a and pT1b stages, and were associated with higher nuclear grades, as demonstrated by our findings with WHO/ISUP grade 3 being the second most common identified, suggesting an aggressive behavior and a poorer prognosis.   The spectrum of adult renal tumors in our region (Mureş County, Romania) aligns with the data reported in the literature. CCRCC was the most frequent histological subtype and pT3a the most common stage identified. Even if in most cases the diagnosis is based on the morphological aspect and IHC profile, in rare cases molecular biology and genetics can help in establishing an accurate diagnosis. Our study contributes to the understanding of renal tumors characteristics, identifying potential factors with impact in the progression and prognosis of the disease.   The authors declare that they have no conflict of interests.   