Clinicopathological Features and Survival Data of Localized Renal Masses in Young Adults

Purpose: Renal tumors are rarely seen in young adults. In this study, was aimed to report the data of 18-40 years old patients with Renal Cell Carcinoma (RCC) whom we operated. Material and Method: We retrospectively reviewed the data of patients between the ages of 18 and 40 years old patients who have renal masses. All patients were evaluated with chest X-ray, Computed tomography (CT) and/or MRI. Radical or partial nephrectomy was performed for clinical localized masses with malignancy suspicion. Clinicopathological features and survival data of all the patients were recorded. In the follow-up protocol routine blood tests, chest X-ray and abdominal CT were used. Results: A total of 42 patients, [22 (52.4%) male and 20 (47.6%) female], with a mean age of 34.48 (range 18 to 40) were included in the study. Of these, 32 (%76) had RCC and 10 (24%) had benign pathologies. Female patients had more benign pathology (35% vs 13.6%). The most commonly subtype of RCC (n = 22% 69) was clear cell RCC (cRCC), while the most common benign mass was oncocytoma (n = 4% 40). At the mean follow-up period of 42.34 months, overall survival rate was found to be 93.8%. Conclusion: Young adults with localized renal mass have benign pathology in a considerable rate. All of the malign masses in this population have low Furhman grade (1 or 2).


Introduction
While RCC is the 8th most commonly diagnosed primary cancer among all adult tumors, it is in 3rd place among all urinary system tumors. Moreover, it the most lethal urinary system tumor (Landis et al., 1999). Approximately 85-90% of RCCs are parenchymal solid tumors (Gunes et al., 2012). It is seen most frequently in the 7th decade. In young adult patients under 40 years it is seen in a very low ratio (3-7%) (Denzinger et al., 2007). Renal tumors at a younger age can be seen as secondary to hereditary syndromes or as sporadic tumors due to undiagnosed gene mutations (Daugherty et al., 2015). It is thought that kidney tumors seen in young adults are different from those seen in older ages. Particularly, it has been claimed that the tumor characteristics, recurrence interval, and treatment response differ from each other (Denzinger et al., 2007;Thompson et al., 2008). In the literature, published data about young adult kidney tumors are contradictory. Some studies have reported that RCC has negative histological features in young adults, but the others have reported it has more favorable histological subtypes and pathologic features than in older patients (Sánchez et al., 2004;Taccoen et al., 2007;Jung et al., 2009).
In the present study, we aimed to report clinicopathological features and survival data of guideline. The follow-up time was calculated as the time from the surgery to the death or the last follow-up. In pathological examination, tumor stage was evaluated according to the 2002 TNM classification and Furhman grading system was used for nuclear evaluation. The disease-free survival (DFS) and overall survival (OS) were used as survival data.

Statistical analysis
Data were analyzed by using Statistical Package for the Social Sciences software package version 20 (SPSS Inc., Chicago, IL, USA). Quantitative data were expressed as mean and range values; categorical data were expressed with frequency (n) and percentages (%). The data were analyzed at 95% confidence level and the threshold for statistical significance was accepted as p < 0.05 for all analyses.

42
(22 male and 20 female) patients were included in the study. The mean diagnose age was 34 year (range: 18-40). All of the patients had unilateral mass. Majority of the patients (79%) were detected incidentally. The majority of the patients (79%) had solid mass. The mean mass sizes were 5.11 cm (range; 2-16) and 5,60 cm (range; 3-10) in malign tumors and in benign tumors, respectively. None of the patients had lymph node positivity or metastases (Table 1).
In RCC patients, grade of tumor is the most important parameter affecting survival (Golimbu et al., 1986;Thrasher et al., 1993). Mohsin et al., (2012) reported survival rates of 1 year and 5 years for stage-1 RCC patients below 40 years of age in 98% and 84%, respectively, whereas in stage-3 RCC patients, these rates were reported as 62% and 50%, respectively. In another study, 5-year survival rate for stage-1 tumors was reported as 88% in patients younger than 40 years (Abou El Fettouh et al., 2002). In our study, mean survival was about 90% over 3.5 years of follow-up. Another important prognostic factor for RCC is the Fuhrman grading system. Prognosis of Fuhrman grade 1-2 tumors are known to be better than grade 3-4 (Gudhjartsson et al., 2005). Fuhrman grade 3-4 was not detected in our series. therefore, it is thought that RCC has better prognosis in this age group.
The retrospective nature of our study, the low number of patients and the lack of comparisons with elderly patients can be regarded as main limitation of our study. On the other hand, the study will contribute to the literature because this study is focused on clinically localized renal masses of 18-40 years of age with restricted data.
In conclusion, young adults with localized renal mass have benign pathology in a considerable rate. Moreover, all of the malign masses in this population have low Furhman grade (1 or 2). So, nephron sparing surgery should be more preferred over radical nephrectomy for localized renal mass in young adults. while 3 patients had distant metastases. Two of these patients were dead. Overall survival rate was 93.8%; disease-free survival rate was calculated as 87.5% (Table 4).

Discussion
In recent years, the incidence of clinically localized renal masses has increased due to improvements in radiological imaging systems (Smith et al., 1989). Despite technological developments it is not possible to distinguish between benign and malignant masses radiologically. In particular, it is not always possible to definitively diagnose benign masses such as focal xanthogranulomatous pyelonephritis, oncocytoma, chronic pyelonephritis and angiomyolipoma before surgery (Remzi et al., 2007). In the literature, of the patients operated with RCC suspicion has been reported to be benign pathologies in 14% -21% of cases (Frank et al., 2003;Thompson et al., 2009). Angiomyolipomas, oncocytomas, adenomas and simple cysts are the most common of these benign lesions. (Duchene et al., 2003;Licht et al., 1995 ). The studies mentioned are related to general populations. In the young adult patient population, the proportion of bening pathologies was reported by Mohsin et al., (2012) as 11%, Yıkılmaz et al., (2015) as 16%, Eggener et al., (2004) as 20.2%. In these studies, benign pathologies such as angiomyolipoma, oncocytoma, simple cyst, hidatic cyst, pyelonephritis and schwannoma were determined at different rates. In our study, benign pathologies were detected in 24% of patients who were operated due to clinically localized renal masses between 18 and 40 years of age. This rate may be considered as high compared to the literature.
It is known that most of the renal masses in young patients are RCC. Earlier studies have shown that kidney masses are approximately 80% malignant; more than 95% of them were found to have RCC (Yıkılmaz et al., 2015;Eggener et al., 2004). Kang et al., (2016) reported that 82% of RCCs in young adults are clear cell RCC, 6% are papillary RCC, and 7% are chromophobe-cell RCC, and 90% of these tumors are T1-2. In another study, 69.5% of malignant masses were reported to be clear cell, 9% to papillary cell and 2% to chromophobe cell carcinoma (Mohsin et al., 2012). In addition to this, there are studies that reported chromophobe cell carcinoma rates higher than 10% in the literature (Lopez et al., 2010;Renshaw et al., 1999). In our study, the most common clear cell carcinoma and at least chromophobe cell carcinoma were determined as similar to the literature.
In studies evaluating the relationship between mass size and histopathology, it was reported that the entire benign masses were smaller than 7 cm (Landis et al., 1999;Duchene et al., 2003). In our study, it was determined that 20% of benign masses were larger than 7 cm, while no significant difference was found between benign and malignant mean mass sizes. This suggests that benign masses larger than 7 cm can be seen in patients aged 18-40 years. Only 2 patients in our series were diagnosed with malignant mass larger than 10 cm and both were reported