Histopathological risk scoring system as a tool for predicting lymph nodal metastasis in penile squamous cell carcinoma

Abstract

Penile cancer is an aggressive neoplasm and nodal metastasis is a key factor in determining the outcome. While there is a paucity of tools predicting nodal metastasis, an elective groin node dissection (GND) may cause severe morbidity. We aimed to devise a histopathology-based risk stratification system to predict the risk of nodal metastasis in penile squamous cell carcinoma (SCC) patients. In this retrospective clinicopathological analysis, consecutive penile SCC patients who had undergone primary surgical treatment with GND from 2007 to 2012 were included. Histopathology slides were reviewed and a histopathological risk scoring system (ranging from 3 to 9) was devised by adding the values assigned to the following pathological variables: tumour grade (1-3); anatomical level of infiltration (1-3); and tumour infiltration pattern (1-3). Three risk groups were created based on histopathological risk scores. Final scores and risk groups were correlated with nodal metastasis, disease-free survival (DFS) and overall survival (OS). We also validated the earlier described prognostic index score (PIS) on our set of patients and compared it to our proposed scoring system. A total of 162 cases of primary penile resections with unilateral or bilateral groin node dissection were identified during the study period. Sixty-two of 68 patients (91.17%) and 58 of 94 patients (61.7%) had nodal metastasis on upfront and follow-up nodal basin surgeries, respectively. Chances of nodal metastasis for each risk group were as follows: low risk (score 3 and 4) 14.3%; intermediate risk (score 5) 52.6%; and high risk (scores 6-9) 83.7%. Follow-up was available in 145 patients (89.5%). Median follow-up was 21 months (1-96 months). The histopathological scoring system (p=0.04) and risk groups (p=0.005) had a statistically significant correlation with DFS but not with OS. Logistic regression model demonstrated that this stratification system was a good predictor of nodal metastasis. Further, this scoring system had better predictive sensitivity for detecting true node-negative cases and marginally better accuracy in detecting nodal metastasis as compared to the PIS. Our study demonstrates that the histopathological risk stratification can predict nodal metastasis and aid in planning management of penile cancer patients with judicious implementation of the morbid procedure of GND.

Keywords: Penile cancer; lymph node metastasis; penile squamous cell carcinoma; prognosis; risk stratification; scoring system.