Aging is a natural intrinsic process associated with the loss of fibrous tissue, a slower cell turnover, and a reduction in immune system competence. In the skin, the continuous exposition of environmental factors superimposes extrinsic damage, mainly due to ultraviolet radiation causing photoaging. Although not usually considered a pathogenic event, photoaging affects cutaneous biology, increasing the risk of skin carcinogenesis. At the cellular level, aging is typified by the rise of senescence cells a condition characterized by reduced or absent capacity to proliferate and aberrant hyper-secretory activity. Senescence has a double-edged sword in cancer biology given that senescence prevents the uncontrolled proliferation of damaged cells and favors their clearance by paracrine secretion. Nevertheless, the cumulative insults and the poor clearance of injured cells in the elderly increase cancer incidence. However, there are not conclusive data proving that aged skin represents a permissive milieu for tumor onset. On the other hand, tumor cells are capable of activating resident fibroblasts onto a pro-tumorigenic phenotype resembling those of senescent fibroblasts suggesting that aged fibroblasts might facilitate cancer progression. This review discusses changes that occur during aging that can prime neoplasm or increase the aggressiveness of melanoma and non-melanoma skin cancer.

Basal cell carcinoma (BCC) is the most common skin cancer, predominantly affecting sun-exposed areas. It typically grows slowly and rarely metastasizes, though untreated cases can cause significant tissue destruction and morbidity. Its pathogenesis primarily involves dysregulation of the Hedgehog (HH) signaling pathway, mainly through mutations in PTCH1 or SMO genes, leading to chronic activation of downstream GLI transcription factors. Accordingly, current targeted therapies for locally advanced, unresectable, or metastatic BCC focus on SMO inhibition, using orally administered drugs such as vismodegib and sonidegib. Although these therapies have shown success, many patients develop resistance, with about 50% harboring mutated SMO. In numerous cases, genetic determinants (sometimes pre-existing) of resistance remain unidentified, complicating patient management. Here, we report a case of a 58-year-old female with advanced BCC who initially exhibited a favorable response to sonidegib but developed resistance after approximately one year. This resistance was not attributable to the acquired mutations in SMO but rather to intra-tumor heterogeneity and additional mutations in critical driver genes, including TP53, APC, FGFR1 and NOTCH1, which likely enable HH pathway inhibition. To our knowledge, this is the first report documenting a sonidegib resistance mechanism in BCC that is independent of HH pathway mutations. This case highlights the complexity of resistance mechanisms to HH inhibitors and underscores the critical need for comprehensive molecular tumor profiling prior to initiating targeted therapy.