Introduction: Keratinocyte tumors (KT) are frequently observed. Surgery is the treatment gold standard. In some cases, a surgical approach might not be the best option. Radiotherapy (RT) and systemic treatments can frequently cause side effects or be contraindicated.

Sun exposure is the main risk factor for cutaneous malignant melanoma (CMM). However, the UV-related pathogenetic mechanisms leading to CMM are far to be fully elucidated. In this paper we will focus on what we still don't fully know about the relationship between UVR and CMM. In particular, we will discuss: the action spectrum of human CMM, how different modalities of exposure (continuous/ intermittent; erythemal/ suberythemal) relate to different CMM variants, the preferential UVR induced DNA mutations observed in different CMM variants, the role of UV-related and UV-unrelated genetic damages in the same melanoma cells. Moreover, we will debate the importance of UVA induced oxidative and anaerobic damages to DNA and other cell structures and the role of melanins, of modulation of innate and acquired immunity, of vitamin D and of chronic exposure to phototoxic drugs and other xenobiotics. A better understanding of these issues will help developing more effective preventative strategies and new therapeutic approaches.

Background Giant basal cell carcinoma (GBCC) is a basal cell carcinoma (BCC) enlarged in a diameter more than 5 cm. Since GBCCs are a highly infrequent entity and the occurrence rate is approximately 0.5-1% out of all BCC types, only anecdotal cases are reported, and causes and characteristics inducing development of this tumor are not defined.Objectives Evaluate causative factors and clinico-histological characteristics of GBCCs.Methods The study is a 6-month, hospital-based case series study performed in 12 Italian dermatologic centers.Results A total of 59 cases and 458 control BCCs were collected. No significant differences existed between the two groups if we take into account social or cultural factors. The average duration of GBCCs is considerably longer than controls. GBCCs are located on unexposed areas while BCCs are on areas not usually covered by clothes. Superficial histological subtype was more frequent in the BCCs group, while infiltrative in GBCCs.GBCCs showed significantly higher local invasiveness, and greater metastatic capacity.More than half of GBCCs had been previously treated with one or more treatments.Conclusions Patients with GBCCs appear to belong to two categories: (i) those who present with GBCC due to delay in accessing medical attention, and (ii) those who have BCCs previously treated with inappropriate strategies. Very few cases could be due to intrinsically aggressive, refractory, or recurrent (after appropriately treated) BCCs. Social and cultural conditions do not appear to be involved in the development of GBCCS. These observations may help clinicians in selecting correct therapeutic strategies in the treatment of BCCs, which give rise to GBCC.