No Detection of Pseudocapsule of Tumor-Parenchyma Interface on Multidetector Computed Tomography (MDCT) Images: Clinical Significance and Histological Reflections in Renal Cell Carcinoma

Objective: Pseudocapsule (PS) of tumor-parenchyma interface (TPI) can be detected by MDCT (ctPS) in renal cell carcinoma (RCC) with exceptions. We aim to study the prognostic implications and histological reflections of no detection of ctPS in RCC.

Patients and methods: A total of 210 RCC patients who had MDCT examination and received nephrectomy in our institution were included in the analysis. Absence or presence of ctPS was recognized, and its associations with overall survival (OS) and progression-free survival (PFS), pathological PS (pPS) and vasculature were studied.

Results: A total of 172 (81.9%) patients were recognized to have a ctPS and 38 (18.1%) had no detection of it. They had comparable histology, stage, grade, and necrosis. Patients without a ctPS had significantly shortened overall survival (OS, p = 0.001) and progression-free survival (PFS, p <0.001), the significance of which persisted in multivariable analysis (OS, HR 3.104, p = 0.003; PFS, HR 3.313, p = 0.001). Nearly all tumors (34/38, 89.4%) without a ctPS actually had a pPS being detected and incompleteness of pPS was also irrelevant (p = 0.739). Compared with ctPS presence, those without a ctPS had significantly thinned pPS (0.36 vs 0.43 mm, p = 0.005). In clear-cell histology, those without a ctPS also contained increased vascular density and cross-sectional area of vessels with long diameter ≥200 um in the pPS layer (p = 0.005 and 0.011) and increased vascular density in the 500 um layer outside pPS (p = 0.017).

Conclusion: Absence of ctPS on MDCT significantly increases the risk of adverse clinical outcome in RCC. It is the reflection of a thinner pPS and enriched vasculature of TPI rather than absence of pPS itself.