Frequency and radiological characteristics of previously overlooked renal cell carcinoma

Abstract

Background

A majority of renal tumors are incidentally detected and may therefore have been previously radiologically overlooked.

Purpose

To investigate the frequency of previously radiologically overlooked renal cell carcinoma (RCC), identify tumor characteristics and imaging factors that contribute to misdiagnoses and to investigate its consequences.

Material and Methods

All RCCs identified in a regional cancer registry over one year were retrieved (n = 87). All preceding radiological examinations were re-analyzed for overlooked RCCs.

Results

RCCs had been previously overlooked in 18 (21%) of the 87 patients (on 26 examinations: computed tomography [CT] = 16, magnetic resonance imaging [MRI] = 5, urography = 3, ultrasound = 2) or 18 (43%) of the 42 patients who had earlier radiological examinations. Overlooked RCCs were smaller than non-overlooked RCCs (median = 23 mm; range = 10–45 mm vs. 65 mm; range = 13–207 mm) (P < 0.0001), more frequently located in upper pole, 50% vs. 26% (P = 0.0836), and more frequently homogenous, 50% vs. 9% (P = 0.0003). There was no difference in exophytic growth (60% vs. 60%) (P = 0.74). Overlooked RCCs displayed poorer visualization on CT/MRI in all image planes (axial, coronal, sagittal) compared to non-overlooked tumors (P = 0.004, P = 0.001, P < 0.0001, respectively). Overlooked tumors had interval size progression of median 12 mm (range = 0–65 mm) to clinical detection (median = 1033 days).

Conclusions

RCCs are frequently overlooked at imaging in the clinical routine. Overlooked tumors were smaller and displayed poorer visualization in all image planes compared to non-overlooked tumors. Substantial delay to clinical diagnosis and variable size progression was noted. Careful attention to the kidneys in multiple image planes seems warranted, irrespective of clinical indication.