Clinical Correlation Between Computerized Tomography Findings and Pathologic Diagnosis in Patients Surgically Treated for Complex Renal Cysts in a Colombian Tertiary Center

Since 1986, the Bosniak radiological classification has become a useful tool for decision making pertaining to patients with renal cystic lesions [1]. In 1993, the IIF group was added to the classification, and since then, in spite of the multiple dilemmas generated around its limitations, there has been an implied understanding that the management of renal cystic lesions depends on the probability of malignancy: low probability (Bosniak I, II, and IIF) vs. high probability (Bosniak III and IV) ) [2,3,4].

For years, clinical practice guidelines have suggested that the management of cystic lesions with a high probability of malignancy should be similar to that of renal masses [5,6]. However, recent studies have demonstrated a more favorable oncological behavior for renal cysts Bosniak III, even reaching the conclusion that this type of lesions could benefit from active surveillance since overtreatment rates have been shown to be as high as 49% [7,8].

In Colombia, there have been no studies that demonstrate the oncological behavior of complex renal cysts. Hence, the present study aims to define and analyze the percentage of malignancy in surgically treated patients for complex renal cysts (Bosniak IIF, Bosniak III, and Bosniak IV) in the urology department of a university hospital in Bogotá, Colombia with the aid of recent global data.

We performed a descriptive study of a series of cases by reviewing the clinical records of patients who had undergone renal surgical procedures (open or laparoscopic nephrectomy/heminephrectomy) at the Hospital Universitario Mayor - Mederi in Bogota, Colombia from February 2010 to January 2018. The records were filtered by surgical indication (renal tumor, non-functioning kidney, complex renal cyst, trauma, etc.), and those cases with a surgical indication for the management of complex renal cyst were selected for analysis. A review of the medical record of every case was performed, including the diagnostic images and/or their official radiology reports, along with the results of the histopathological studies. The frequency of the different pathological diagnoses assigned to each patient was evaluated. Cases with incomplete clinical information (demographic data, surgical indication, CT images or their official reports, and pathology results) were excluded from our analysis. The results are expressed in absolute and relative frequencies for the qualitative variables, while the quantitative variables are presented in the form of average measures.

During the study period, 235 renal surgical procedures were performed (open or laparoscopic nephrectomy/heminephrectomy) in the urology department of the Hospital Universitario Mayor- Mederi. Nine patients were excluded from our analysis as they did not have complete information for the study. Of the remaining 226 patients, 14 (6.19%) were found to have been surgically treated for complex renal cysts. All of these patients had taken a scan of the abdomen and pelvis as part of their imaging studies; only one patient had an MRI performed in addition to CT.

Of the patients who had undergone surgery for the management of complex renal cyst, five (38.46%) presented image findings compatible with Bosniak IIF, six (46.15%) with Bosniak III, and two (15.38%) with Bosniak IV; and one patient was excluded because there was no radiological image or report available (Table 1).

Five (38.46%) of the patients were females, and 8 (61.54%) were males. The average age was 59.23 years (range: 34-72 years). The average size of the renal cystic lesion was 50.81 x 38.72 mm. None of the patients had presented metastatic involvement at the time of diagnosis. In the group of patients with imaging lesions classified as Bosniak IIF (n = 5), three (60%) had an oncological diagnosis in the pathology report (100% clear cell renal carcinoma). Within the group corresponding to the Bosniak III classification (n = 6), two cases (33.33%) had been initially classified as Bosniak IIF but had progressed to Bosniak III during the follow-up. In this group, four (66.7%) patients had presented pathological diagnosis after surgical resection (50% clear cell renal carcinoma, 25% multilocular cystic neoplasm, and 25% nonspecific tumoral cystic lesion). In the group corresponding to the Bosniak IV classification, both (100%) patients had received a pathological diagnosis of clear cell renal carcinoma.

Surgical indications in the group of patients with Bosniak IIF renal cysts are described in Table 2. Four (80%) patients undergoing surgical management for Bosniak IIF lesions had received treatment by laparoscopic heminephrectomy. The remaining case was managed by radical laparoscopic nephrectomy. One case had presented a tumor recurrence after three years of follow-up, which had required a new laparoscopic tumorectomy.

Four (66.7%) patients with complex renal cysts Bosniak III had undergone surgical management by laparoscopic heminephrectomy; the remaining two (33.3%) had undergone radical laparoscopic nephrectomy. All patients with Bosniak IV complex kidney cysts had had laparoscopic radical nephrectomy performed because of the described proximity of the lesions to the interpolar region and the collecting system.

The modified Bosniak radiological classification is an immensely useful tool for surgical decision making pertaining to patients at risk of renal cystic neoplasia. Historically, it has been estimated that between 5 and 10% of cases of renal cancer originate from renal cystic pathology [8,9]. Recently, an update to the Bosniak classification was proposed, with the addition of MRI criteria, with an intention to improve the ability of the original classification to predict the likelihood of malignancy in a cystic renal lesion [10]. In our study, which focused on the group of patients with an indication of surgical management, we found that 6.9% of cases of renal cancer were initially associated with complex renal cysts.

Unlike the global studies conducted in recent years, the percentage of patients with oncological disease was higher in our sampled population [11-17]; 60% and 66.7% of malignancy evidenced in patients with renal cysts Bosniak IIF and III in this study are a far cry from the results recently reported by Schoots et al. (14% and 51%, respectively) [8]. When we performed a comparative analysis against the published literature of recent years, the percentage of malignancy found in our group of patients with renal cysts Bosniak IIF and III was found to be higher (Table 3).

Despite the limitations derived from our sample size, it is necessary to highlight that, of the patients with a reported Fuhrman nuclear grade in this study, 50% of patients presented grades 3 and 4 (high grades). These results contrast with the experiences described by Hwang et al., Mousessian et al., and Donin et al., who described a higher proportion (73%, 91%, 93.7%, respectively) of patients with low-grade Fuhrman grades (1 or 2) in patients with cystic renal carcinoma [11,13,14]. In spite of the significant percentage of patients with high-grade oncological lesions, none of the patients included in this study had metastatic compromise at the time of diagnosis and only one patient had a tumor recurrence. In the group analyzed, of the total number of patients who received an oncological diagnosis by histopathological analysis, 77.7% (n = 9/14) of cases had clear cell renal carcinoma; this finding in terms of frequency is similar to that described in recent literature globally [17].

We are aware that the present study has limitations, mainly related to the size of the sample, the selection of patients who were taken solely to surgical management (selection bias), and the interpretation of the diagnostic images by different radiologists (interobserver variability). But regardless of these limitations, the percentage of patients with complex renal cysts Bosniak IIF and Bosniak III who received oncological diagnosis was found to be higher than the average described in the current medical literature. Therefore, based on the results found, it is not possible to assume that renal cysts Bosniak IIF and III present a low proportion of malignancy in our environment. The results presented here constitute the first study of its kind conducted in Colombia, and demonstrate the need to pay close attention to the risk-benefit ratio generated by any medical intervention in patients with complex renal cysts (active surveillance vs. surgical management).

Thus, the management of complex renal cysts in a local setting must have an individualized approach, which should be adapted to the individual risk characteristics for cancer, and to the possibilities and assurances in providing a strict follow-up for patients with Bosniak IIF and III complex cysts. The findings presented in this article endorse the idea of tailoring a management strategy not very different from that found in current clinical practice guidelines for patients with complex renal cysts (Bosniak III and IV) and localized renal masses. Furthermore, the results call for a stricter periodical follow-up for patients with renal cysts Bosniak IIF given the high percentage of malignancy observed.

The Bosniak radiological classification is a useful tool for estimating the probability of malignancy in renal cysts. In this study, the percentage of malignancy in patients with renal cysts Bosniak IIF and III was found to be greater than that described in recent literature. The most frequent type of cancer was clear cell renal carcinoma, and no patient had metastatic involvement at the time of diagnosis. The findings demonstrate the need to provide strict monitoring in a local environment for patients with Bosniak IIF renal cysts, and to offer oncological management similar to localized renal masses for patients with renal cysts Bosniak III and IV.