Invasive cutaneous verruco-cystic squamous cell carcinoma. A pattern commonly present in transplant recipients.

To determine whether certain histologic features are more common in cutaneous squamous cell carcinomas (CSCCs) arising in transplant recipients than in others, we assessed several features of CSCCs from 23 patients who had not undergone transplantation and 25 transplant recipients (size, depth of invasion, sun damage, nuclear atypia, keratinization, epidermal inclusion cyst [EIC]-like features, verrucous features [VFs], shape, and mitoses per 10 high-power fields). We analyzed relationships by using chi 2 and t tests and logistic regression analysis. Transplant recipients tended to be younger than control subjects (mean [SD] age, 56.2 [14.3]; 74.1 [10.6], respectively; P < .0001) and less likely to show severe sun damage (P = .0455; chi 2). CSCCs with VFs and EIC-like features were associated strongly with transplantation: odds ratio, 12.57 (95% confidence interval, 1.28-123.47; P = .0162). No other features were associated significantly with transplant status. Posttransplant tumors commonly showed verrucous and EIC-like features mimicking benign conditions. The younger age of these patients, the frequent absence of solar elastosis, and the infrequent occurrence of well-differentiated verruco-cystic CSCC in the nontransplant population suggest a different pathogenesis in the development of these neoplasms. Pathologists should be aware of this pattern, especially when diagnosing small biopsy specimens from transplant recipients.