Sun-Exposed versus Sun-Protected Cutaneous Basal Cell Carcinoma: Clinico-Pathological Profile and p16 Immunostaining.

Introduction: Although widespread, BCC is still relatively poorly understood in regards to pathogenesis and prognosis, particularly the lesions formed on anatomical sites away from sun exposure. With the aim of deepening our understanding of the pathogenesis and clinico-pathological correlations of BCCs, we conducted this study.

Methods: Tissue blocks and data of 52 Egyptian patients diagnosed with BCC were retrieved for clinical information and inclusion criteria, then re-examined histologically; p16 immunostaining was carried out and evaluated for analysis and comparison between the two groups, i.e., sun-exposed and sun-protected.

Results: Sex, age, clinical suspicion, tumor size, recurrence status, and histologic variants did not show a significant difference between the sun-protected and sun-exposed groups; however, the mean ages recorded were 67.2 vs. 62.7 for the sun-protected and sun-exposed groups, respectively. A total of 52% of BCCs were positive for p16. The sun-protected lesions showed p16 positivity in 61% of cases, whereas 49% of the sun-exposed lesions were positive with no significant difference. There was a significant difference in p16 expression between the recurrent and non-recurrent lesions.

Conclusions: A significant difference was seen in the case of cancer recurrence, where all the recurrent BCCs in this study demonstrated negative p16 immunostaining of the primary lesions; however, the positively stained cases in total were 52% of BCCs. The mean patient age of the sun-protected group was much higher than in previous peer studies. We assume that the biological, prognostic, and clinical aspects of p16 protein expression in BCCs are still far from being clearly understood. Further studies are highly recommended, with more focus on its role in the pathogenesis and the prognostic factors.