Best Cases from the AFIP

The Modified Bosniak Classification for Intermediate-Risk Renal Cysts in Children

OBJECTIVES

To examine correlations of the modified Bosniak categories assigned by radiologists to histological results and inter-rater reliability, focusing on intermediate-risk lesions.

MATERIALS AND METHODS

The data of pediatric patients who underwent surgery for intermediate-risk complex renal cyst at a tertiary medical center in 2006-2019 were collected retrospectively. Four pediatric radiologists from 2 different medical centers reviewed the available imaging scans, and assigned each to one of the four modified Bosniak classification categories. Binary cohorts of the Bosniak categories (I-II vs III-IV) were compared to the histological results. Diagnostic accuracy (benign- vs intermediate-risk lesion) was calculated for each radiologist and for each imaging modality. Krippendorff's α test was used to measure inter-rater reliability.

RESULTS

The cohort included seven children, each with 1 complex cyst that was rated as intermediate-risk on pathological study. The median age was 1.5 years (IQR 1, 11.9). A correct classification was made in 41/56 imaging readings (sensitivity 73.2%). Applying Krippendorff's test to the binary Bosniak cohorts yielded poor inter-rater agreement (α = 0.08).

CONCLUSION

Implementation of the modified Bosniak classification in children caused a disconcerting underestimation of intermediate risk. There was a low inter-rater consistency for the categories intended to guide decisions regarding surgery or conservative management. The findings suggest that clinicians should be cautious using the modified Bosniak system for children.

Contemporary update on imaging of cystic renal masses with histopathological correlation and emphasis on patient management

This article presents an updated review of cystic renal mass imaging. Most cystic renal masses encountered incidentally are benign and can be diagnosed confidently on imaging and require no follow-up. Hyperattenuating masses discovered at unenhanced or single-phase enhanced computed tomography (CT) measuring between 20-70 HU are indeterminate and can be further investigated first by using ultrasound and, then with multi-phase CT or magnetic resonance imaging (MRI); as the majority represent haemorrhagic/proteinaceous cysts (HPCs). Dual-energy CT may improve differentiation between HPCs and masses by suppressing unwanted pseudo-enhancement observed with conventional CT. HPCs can be diagnosed confidently when measuring >70 HU at unenhanced CT or showing markedly increased signal on T1-weighted imaging. Although the Bosniak criteria remains the reference standard for diagnosis and classification of cystic renal masses, histopathological classification and current management has evolved: multilocular cystic renal cell carcinoma (RCC) has been reclassified as a cystic renal neoplasm of low malignant potential, few Bosniak 2F cystic masses progress radiologically during follow-up; RCC with predominantly cystic components are less aggressive than solid RCC; and Bosniak III cystic masses behave non-aggressively. These advances have led to an increase in non-radical management or surveillance of cystic renal masses including Bosniak 3 lesions. Tubulocystic RCC is a newly described entity with distinct imaging characteristics, resembling a pancreatic serous microcystadenoma. Other benign cystic masses including: mixed epithelial stromal tumours (MEST) are now considered in the spectrum of cystic nephroma and angiomyolipoma (AML) with epithelial cysts (AMLEC) resemble a fat-poor AML with cystic components.

Renal Tumors of Childhood: Radiologic-Pathologic Correlation Part 1. The 1st Decade: From the Radiologic Pathology Archives

Wilms tumor is the second most common pediatric solid tumor and by far the most common renal tumor of infants and young children. As most tumors are large at presentation and are treated with nephrectomy, the role of imaging is primarily in preoperative planning and evaluation for metastatic disease. However, with treatment protocols increasingly involving use of preoperative (neoadjuvant) chemotherapy (the standard in Europe) and consideration of nephron-sparing surgery, the role of imaging is evolving to include providing initial disease staging information and a presumptive diagnosis to guide therapy. Differential diagnostic considerations include lesions that are clinically benign and others that require more intensive therapy than is used to treat Wilms tumor. In part 1 of this article, the unique histologic spectrum of renal neoplasms of infants and young children is reviewed with emphasis on radiologic-pathologic correlation. Part 2 will focus on renal tumors of older children and adolescents.

Segmental multicystic dysplastic kidney in an adult: usefulness of enhanced CT in excretory phase

We present an adult case of segmental multicystic dysplastic kidney (SMCDK). The patient had a 10 × 6 cm oval-shaped mass consisting of a solid and multilocular cystic component at the right upper renal sinus. The solid component showed gradual and mild enhancement on dual-phase enhanced CT. Excretory-phase CT demonstrated the excretion of contrast medium into the septa and cysts. Dilation of the upper calices and renal pelvis and atretic renal pelvis in the mass were also clearly visualized in the excretory phase. The signal intensity of the solid component was slightly lower than that of the renal parenchyma on T2-weighted images and similar to that of the medulla on diffusion-weighted images. Right nephrectomy showed a multilocular cystic component within the renal sinus and some of the cysts contained blood. The renal pelvis of the upper moiety was blind, as suggested by CT. Microscopically, there were multiple non-communicating small cysts, as shown by CT, and the wall was lined with immature tubule-like cells. In addition, immature tubule-like cells were seen in the septa. Immature mesenchymal cells were seen around the cysts. The solid component mainly consisted of fibroconnective tissue with immature tubule-like cells. The pathological diagnosis was confirmed as SMCDK. Excretion of contrast media into the septum and cystic component might be a characteristic finding of SMCDK in addition to the finding of a multilocular cystic mass in the upper moiety with urinary tract abnormality.

Case report: a left upper quadrant complex cystic mass

A 61-year-old woman presented with left upper quadrant/flank pain and increasing abdominal girth. CT scan showed a large complex, multi-cystic lesion in the left abdomen. Laparotomy revealed a large retroperitoneal mass attached to the left kidney. Left nephrectomy was performed and pathology demonstrated a benign cystic nephroma. Surgical oncologists should be aware of this rare renal lesion as the clinical and radiographic presentation may mimic other intra-abdominal cystic lesions.

Bilateral cystic nephroma with pleuropulmonary blastoma

Cystic nephroma is a rare benign renal neoplasm that is purely cystic and is lined by an epithelium. Bilateral cystic nephromas are even rarer with only a handful cases reported in the literature. A case of a 2-year-old male child who presented with bilateral renal cystic masses later diagnosed as cystic nephromas is presented here. Ultrasound, CT scan and histopathological investigations aided in arriving at the correct diagnosis. The most concerning feature was the presence of a fluid filled cystic mass in the lungs, most probably a pleuropulmonary blastoma which is a rare malignant neoplasm known to be associated with bilateral cystic nephromas. The most common presenting symptoms of cystic nephroma are painless abdominal mass, abdominal or flank pain and haematuria. These tumours usually follow a benign course and nephrectomy alone is curative. A close surveillance of such patients is recommended because of elevated risk of other tumours.

Pleuropulmonary blastema with cystic nephroma - A rare presentation and surgical dilemma

Pleuropulmonary balstema with cystic nephroma is a rare dual pathology of pediatric age group. The etiopathogenesis of this entity is not known, still researches indicate towards a common genetic cause. We report a case of this dual pathology in a one and half year old male. Till now only 5 cases have been reported.

Unusual Case of Multilocular Cystic Nephroma Treated with Nephron Sparing Technique: A Case Report

Multilocular cystic nephroma is an unusual entity of uncertain etiology that can affect children and adults equally. This lesion is believed to be part of a spectrum of renal cystic disorders with multilocular cyst and cystic Wilms' tumor representing the two extremes and usually presents with a benign character. We report a 22-year-old female who presented with a painful right renal mass and gross hematuria. After a series of examinations including abdominal ultrasound, computed tomography, and angiography, she underwent partial nephrectomy under the impression of benign lesion. The pathologic examination showed that it was a multilocular cystic nephroma. At the 11-month follow-up, the patient was completely asymptomatic and free of recurrence and metastasis.