Predictors of Recurrence and Progression in Poorly Differentiated Cutaneous Squamous Cell Carcinomas: Insights from a Real-Life Experience

Introduction Surgery represents the primary treatment option for cutaneous squamous cell carcinoma (cSCC) aiming for complete tumor resection (R0). Recurrence and metastasis significantly affect survival and outcomes, and poorly differentiated (G3) cSCC is associated with a higher risk of recurrence. However, the specific clinical and histopathological features that predict recurrence and progression in G3-cSCC remain unclear. Methods A retrospective analysis was conducted on a series of patients with primary G3-cSCC diagnosed at the Turin University Hospital between January 2016 and January 2021. After independent histological revision, logistic regression models were used to identify clinico-pathological predictors of cutaneous recurrence, lymphnode/metastatic progression, and both types of progression. Results Among the 161 G3-cSCC patients, 80.1% (129/161) showed no signs of local recurrence or metastatic progression, while 19.9% (32 patients) had progressed. In the univariate logistic regression, tumor clinical diameter, depth of infiltration (DOI), and lymphovascular invasion (LVI) were identified as significant predictors across the various types of progression (p<0.05). In the context of multivariate logistic regression, distinct models proved to be significant. For skin recurrence, a 3-variable model incorporating DOI (OR 1.16, 95% CI 1.01-1.35, p=0.050), LVI (OR 3.61, 95% CI 1.11-11.8, p=0.034), and desmoplasia (OR 3.45, 95% CI 1.25-9.5, p=0.017) was selected. Regarding lymphnode/metastatic progression, a 3-variable model combining pT2 (OR 6.10, 95% CI 1.15-32.35, p=0.034), pT3 (OR 14.33, 95% CI 2.79-73.63, p=0.001), and LVI (OR 3.86, 95% CI 1.10-13.62, p=0.036) was identified. Lastly, a 2-variable model for both types of progression consisted of vertical tumor thickness (OR 5.45, 95% CI 1.11-27.32, p=0.039) and LVI (OR 1.15, 95% CI 1.04-1.26, p=0.006). Conclusion Tumor size, depth of infiltration, and LVI were significant predictors of recurrence and metastatic progression. Notably, the size of histologically defined tumor-free margins did not affect the risk of recurrence, whilst LVI emerged as a key predictor of all forms of progression. These findings provide insights into risk stratification and suggest that close monitoring and potential adjuvant therapies, such as radiation therapy, may be necessary especially for patients with lymphovascular involvement.