Joanna Moser MBChB, Presenter: Nothing to Disclose

Joy Barber MBBS, MA, Abstract Co-Author: Nothing to Disclose

Brendan Tinwell MBBS, Abstract Co-Author: Nothing to Disclose

Cathy Corbishley, Abstract Co-Author: Nothing to Disclose

Uday Patel MD, Abstract Co-Author: Nothing to Disclose

Type 2 pRCC are more aggressive than type 1 pRCC. Recent studies have described CT features of types 1 and 2 pRCC, but without non-pRCC controls. The aims of this study were: 1. Define the accuracy of CT for differentiating pRCC from non-pRCC 2. Define the accuracy of CT for differentiating type 1 pRCC from type 2 pRCC 3. Assess the diagnostic value of individual CT features for diagnosis of pRCC

CT scans of 114 patients (mean age =64 years, range 32-85 years) with histologically confirmed malignant renal masses underwent blinded radiological review without knowledge of the pathology. Each mass was assigned as type 1 pRCC, type 2 pRCC or non-pRCC, using previously described radiological features of each subtype. The presence of individual CT features was noted. Separate pathological review confirmed 26 as type 1 pRCC, 9 as type 2 pRCC, 63 as clear cell RCC and the rest as miscellaneous tumour types. Results were used to calculate overall diagnostic accuracy and odds ratios (OR) for individual CT features.

Patients with pRCC and non-pRCCs were matched for age/sex/tumour stage. Specificity and sensitivity of CT for the diagnosis of pRCC was 75% and 55% respectively, with a negative predictive value of 78%. Comparable figures for subtyping of type 1 and 2 pRCC were specificity 75% and sensitivity 20%. Regarding the value of individual CT signs, pRCC enhanced less than non-pRCCs, with a mean post contrast density rise of 31HU vs. 55HU (p=0.0001; unpaired t-test). pRCCs were significantly more likely to demonstrate homogenous enhancement (OR 2.9), round or oval vs. complex shape (OR 7.4), calcification (OR 5.7), solid vs. cystic or necrotic appearance (OR 8.8) and have a smooth vs. irregular edge (OR 3.9). Centripetal growth was less common in pRCC. Regarding subtyping of pRCC, a smooth tumour edge was more common in type 1 (p=0.007). Other described subtyping CT signs of pRCC were not found to be useful (p>0.5).

A homogenous, solid, round or oval shaped renal mass with a smooth edge and low-level enhancement is more likely to be a pRCC with odds ratios of 2.9-8.8. Types 1 and 2 pRCCs cannot be reliably differentiated from each other.

Papillary RCC can be reliably predicted from CT features using the described CT signs. However, there is an overlap between the described CT signs of types 1 and 2 pRCC, and biopsy for subtyping of pRCC should be considered.

Moser, J, Barber, J, Tinwell, B, Corbishley, C, Patel, U, Identifying Subtypes of Papillary Renal Cell Carcinoma (pRCC) on CT – Accuracy and Distinguishing Features.  Radiological Society of North America 2014 Scientific Assembly and Annual Meeting, - ,Chicago IL. http://archive.rsna.org/2014/14015187.html