Association between the clinical and histopathological classifications of actinic keratosis and the efficacy of topical imiquimod treatment

The emerging role of mast cells in skin cancers: involved cellular and molecular mechanisms

Skin cancers are the most common cancers worldwide. They can be divided into nonmelanoma skin cancers (NMSC) including basal cell carcinoma (BCC), squamous cell carcinoma (SCC), and less common lymphomas and merkel cell carcinoma, and melanomas. Melanomas comprise less than 5% of skin cancer rate but are responsible for more than 90% of skin cancer death. Mast cells (MCs) are multifunctional cells that play an important role in inflammatory and allergic reactions. They attract other key players of the immune system by releasing cytokines. Healthy human skin comprises MCs under physiological status, and the number can increase under certain conditions including skin malignancies postulating their possible role in pathogenesis of and immunity against skin cancers. MCs respond to cytokines released by tumor stromal cells, release mediators (including histamine and tryptase), and induce the neovascularization, degradation of extracellular matrix (ECM), and induce mitogenesis. However, MCs may use molecular mechanisms to exert immunosuppressive activity including releasing complement C3, lower expression of CD40L, and overexpression of enzymes with vitamin D3 metabolizing activity including CYP27A1 and CYP27B1. This review summarizes the current knowledge on the role of MCs in pathogenesis and immunity against skin cancers.

Follicular extension of atypical keratinocytes predicts the resistance of actinic keratosis to topical imiquimod treatment: A single-center retrospective analysis

Topical imiquimod therapy has been widely used for actinic keratosis (AK). However, some cases are refractory to treatment. Therefore, an indicator that can predict its efficacy is desired. Herein, we retrospectively analyzed 52 AK lesions treated with imiquimod to investigate the characteristics of refractory lesions. Imiquimod was applied in a cycle of three times weekly for 4 weeks, followed by a 4-week break. This treatment cycle was repeated up to three times and treatment responses were evaluated. As a result, a complete response (CR) was observed in 78.8% (41/52) of lesions. Next, treatment response of lesions was correlated with clinicopathological characteristics including clinical morphology and thickness, pathological morphology and thickness, and presence of follicular extension (FE). Of these, lesions with FE were significantly less responsive to imiquimod treatment; while 92.6% of AK lesions without FE achieved a CR, only 64.0% of AK lesions with FE achieved a CR (p = 0.029). Logistic regression analysis revealed that FE was the sole significant predictor of its efficacy (p = 0.019). These results suggest that preliminary histological evaluation of FE may be useful to predict the efficacy of imiquimod for AK.

Current developments in pharmacotherapy for actinic keratosis

INTRODUCTION

Actinic keratosis (AK) is a superficial squamous cell carcinoma (SCC) where chronic sun exposure playing central role in its pathogenesis. UVB causes direct damage to DNA, producing pyrimidine dimers, and suppressing the protective role of p53. The stepwise progression of AK, with increased expression of anti-apoptotic Bcl-2, favors progression to SCC. Moreover, the dermal response characterized by inflammation and mediated by prostaglandins is a critical component of tumorigenesis that promotes tumor growth, tissue invasion, angiogenesis and metastasis. Other risk factors are represented by age, gender, phototype and drugs.

AREAS COVERED

In this review, the authors document the recent developments of different therapies used to treat AK and provide their perspectives on current and future treatment strategies.

EXPERT OPINION

The usefulness of long-term treatment with piroxicam and sun filters or diclofenac targeting the inflammation phases of skin tumorigenesis favors AK's healing and provides greater control of the cancerization field. Nonsteroidal anti-inflammatory drugs can be safely used in patients who use photosensitizing drugs and, therefore, are more at risk of developing skin tumors. Immunomodulatory therapies, which require shorter treatment, are characterized by more common local side effects, and need more attention by the dermatologist in the concern of patient education, resulting essential to improve adherence and outcomes.