Cutaneous squamous cell carcinoma and related entities: Epidemiology, clinical and histological features, and basic science overview

Keratoacanthoma versus Squamous-Cell Carcinoma: Histopathological Features and Molecular Markers

Considerable controversy exists within the field of dermatopathology in differentiating keratoacanthoma (KA) from squamous-cell carcinoma (SCC). KAs are rapidly growing, benign squamous tumors that are typically well differentiated. This controversy stems from the diverging perspectives on the management, classification, and diagnosis of each entity. Many believe that KAs are benign neoplasms in which intervention may be unnecessary since they are self-limiting and resolve on their own. On the other hand, SCC needs to be treated, as it carries significant morbidity and mortality risks. Early diagnosis and treatment are vital to prevent serious consequences of SCC. Nevertheless, KAs may resemble SCC grossly and microscopically. Various ancillary tests, including immunohistochemical (IHC) staining, have been proposed to differentiate between these entities, though mixed patterns of expression can limit the diagnostic utility of these techniques. Research into this topic is ongoing, with newer genetic and molecular findings illuminating the previously difficult-to-understand aspects of KA and increasing our understanding of this entity. In this review, KA and SCC will be compared along the lines of histological features, genetic, immune, and molecular markers, differential diagnosis, and management to clarify the similarities, differences, and misconceptions about both entities.

Management Approaches for High-Risk Cutaneous Squamous Cell Carcinoma with Perineural Invasion: An Updated Review

Cutaneous squamous cell carcinoma (cSCC) stands as the second most prevalent non-melanoma skin cancer worldwide, comprising approximately 20% of all cutaneous malignancies. Determining its precise incidence poses challenges; however, reports indicate a global increase in its prevalence. At the time of diagnosis, the majority of cSCCs are localized, resulting in favorable 5-year cure rates surpassing 90%. Nevertheless, a subset of patients (3-7%) encounters locally advanced or metastatic cSCC, leading to substantial morbidity and mortality. The risk of metastasis ranges from 0.1% to 9.9%, carrying an associated mortality risk of 2.8%. Factors influencing recurrence, metastasis, and disease-specific mortality underscore the significance of perineural invasion (PNI) as a key indicator. Patients with PNI may manifest clinical symptoms and/or radiologic signs of PNI, while the majority remain asymptomatic, and PNI is frequently identified upon histologic examination. Despite its lower frequency compared to other cancer types, PNI serves as a recognized adverse prognostic factor for cSCC. Surgery is the elective treatment for these patients, while the role of adjuvant radiotherapy (ART) is yet contentious and have not been conclusively assessed, particularly in clear surgical margin. Prospective comparative studies are required to comprehensively evaluate the benefit and the risks of ART for cSCC and PNI patients.

Reconceiving Perineural Invasion in Cutaneous Squamous Cell Carcinoma: From Biological to Histopathological Assessment

BACKGROUND

Perineural invasion (PNI) is a complex molecular process histologically represented by the presence of tumor cells within the peripheral nerve sheath and defined when infiltration into the 3 nerve sheath layers can be clearly identified. Several molecular pathways have been implicated in cSCC. PNI is a well-recognized risk factor in cutaneous squamous cell carcinoma (cSCC) and its accurate assessment represents a challenging field in pathology daily practice.

SUMMARY

As a highly intricate and dynamic process, PNI involves a contingent on bidirectional signaling interactions between the tumor and various nerve components, such as Schwann cells and neurons. The current staging systems recommend the identification of PNI as a dichotomous variable (presence vs. absence) to identify a subgroup of high-risk patients. However, recent further insights revealed that the evaluation of morphological PNI-related features in cSCC may enhance the prognostic stratification of patients and may optimize the current staging guidelines for recurrence risk assessment and improvement of patient selection for postoperative adjuvant treatments. Furthermore, recent emerging biomarkers could redefine early PNI detection.

KEY MESSAGES

This review provides updated insights into cSCC with PNI, focusing on molecular and cellular pathogenic processes, and aims to increase knowledge on prognostic relevant PNI-related histological features.

From the Cochrane Library: Visual Inspection and Dermoscopy, Alone or in Combination, for Diagnosing Keratinocyte Skin Cancers in Adults

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Innovative Topical Patches for Non-Melanoma Skin Cancer: Current Challenges and Key Formulation Considerations

Non-melanoma skin cancer (NMSC) is the most prevalent malignancy worldwide, with approximately 6.3 million new cases worldwide in 2019. One of the key management strategies for NMSC is a topical treatment usually utilised for localised and early-stage disease owing to its non-invasive nature. However, the efficacy of topical agents is often hindered by poor drug penetration and patient adherence. Therefore, various research groups have employed advanced drug delivery systems, including topical patches to overcome the problem of conventional topical treatments. This review begins with an overview of NMSC as well as the current landscape of topical treatments for NMSC, specifically focusing on the emerging technology of topical patches. A detailed discussion of their potential to overcome the limitations of existing therapies will then follow. Most importantly, to the best of our knowledge, this work unprecedentedly combines and discusses all the current advancements in innovative topical patches for the treatment of NMSC. In addition to this, the authors present our insights into the key considerations and emerging trends in the construction of these advanced topical patches. This review is meant for researchers and clinicians to consider utilising advanced topical patch systems in research and clinical trials toward localised interventions of NMSC.

Research on Correlations of miR-196a Expression with Progression and Prognosis of Cutaneous Squamous Cell Carcinoma

PURPOSE

This study aimed to investigate the correlation between miR-196a expression and the progression and prognosis of cutaneous squamous cell carcinoma (CSCC).

PATIENTS AND METHODS

Tissue samples and corresponding paracancerous tissue samples from 117 patients with CSCC were collected. The qRT-PCR analysis was used to detect the expression levels of miR-196a. Kaplan-Meier curve and Cox regression analyses were used to analyze the relationship between miR-196a expression and patients' prognosis. The CCK-8 and transwell assays were used to explore the effects of miR-196a on the abilities of cell proliferation, migration, or invasion.

RESULTS

miR-196a expression was significantly up-regulated in CSCC tissues or cell lines, compared with adjacent normal tissues or cell lines, respectively. High expression of miR-196a was associated with positive lymph node metastasis, high TNM stages, and a lower five-year survival rate. The expression level of miR-196a was up-regulated and the proliferation, migration or invasion ability of cells were significantly increased accordingly.

CONCLUSION

miR-196a is highly expressed in CSCC, thus affecting the occurrence and development of CSCC. More importantly, miR-196a was shown to have potential as a prognostic marker for CSCC.

Factors accelerating recurrences and secondary tumors in cutaneous squamous cell carcinoma

To investigate factors that affect and also decrease the duration for recurrences and secondary tumors in cSCC. A retrospective study was conducted for all patients who were treated for a cSCC of the head and neck between 2009 and 2016. Anamnestic as well as epidemiological and histological data were noted and correlated with the occurrence of recurrences and secondary cancers. The duration between surgery and these events was used to determine if histological factors accelerate their occurrence. The highest risk for recurrences was seen in patients with previous skin cancers (RR 3.23). Histological ulceration (p = 0.003) and grading (p = 0.031) of the tumor were found as significant factors accelerating the time to relapse. Surrounding chronic precancerotic lesions (p < 0.001) and poor tumor grading (p = 0.035) were found as significant factors accelerating the time until a secondary cSCC was observed. Known risk factors increase not only the risk for a cSCC but also for recurrences. Specific histologic findings can help to adjust follow-up intervals to identify recurrences and secondary tumors at an early stage as these were shown to decrease the duration for a further event.

Retrospective evaluation of the performance of the electrical impedance spectroscopy system Nevisense in detecting keratinocyte cancers

BACKGROUND

Keratinocyte cancers, also referred to as non-melanoma skin cancers (NMSCs), are one of the most common malignant skin tumors. We performed a retrospective analysis of lesions from patients of a private dermatology practice to evaluate the use of electrical impedance spectroscopy (EIS) in detecting keratinocyte malignancies. The aim of the study is to assess the accuracy of the technique and to rate its use as supportive tool in NMSC diagnosis.

MATERIAL AND METHODS

The period evaluated ranges from September 2015 to November 2019. In total, 1712 lesions from 951 patients were included. All lesions suspicious for malignancy were gauged with the Nevisense device. Excised lesions were sent in for histopathological classification, and the results were compared to the Nevisense score.

RESULTS

A total of 767 lesions (44.8%) received a negative score (0-3) from the Nevisense system and 945 lesions (55.2%) a positive score (4-10). The combination of the dermatologist's visual assessment plus the technical determined Neviscore resulted in the excision of 52.5% of all 1712 suspicious lesions whereof 15% were found to be malignant. The sensitivity of Nevisense was 98.4% for NMSC detection.

CONCLUSION

Electrical impedance spectroscopy was found to be a valuable adjunct support tool in clinical decisions for cases with suspicion for NMSC.

Immunotherapies in cutaneous pathologies: an overview

Skin is a vital protective organ, the main role of which is to provide a physical barrier and to prevent the entry of pathogens. Various pathologies, such as atopic dermatitis (AD), psoriasis (PSO), or skin cancers, can affect the skin, and all show a high and increasing prevalence. Many antibodies are currently used in the treatment of these diseases. However, various studies are underway for the development of new biologics directed against specific targets. In this review, we describe current biologics used in skin pathologies as well as antibodies in development. We also discuss various immunotherapy examples that use new delivery technologies, such as microneedle patch, nanoparticles (NPs), liposomes, or gel formulation.

Targeting 14-3-3ε-CDC25A interactions to trigger apoptotic cell death in skin cancer

Non-melanoma skin cancer is the most common form of cancer worldwide. We previously documented an anti-apoptotic role for CDC25A in cutaneous squamous cell carcinoma (SCC), an activity dependent on its association with 14-3-3 proteins. We hypothesized that targeting CDC25A-14-3-3ε interactions may be an effective strategy for inducing skin cancer cell apoptosis. Co-immunoprecipitation revealed that CDC25A associated with 14-3-3ε, 14-3-3γ and 14-3-3ζ in SCC cells but not normal keratinocytes. 14-3-3ε and CDC25A activated Akt/BAD/Survivin pro-survival signaling. To target the interaction of 14-3-3ε with CDC25A for cancer therapy, we developed two novel phospho-peptides, pS and pT, corresponding to each of the 14-3-3 binding sites of CDC25A, to specifically interfere with 14-3-3ε binding to CDC25A. Peptides pT (IC₅₀ = 22.1 μM), and pS (IC₅₀ = 29 μM) induced SCC cell death and blocked 14-3-3ε binding to CDC25A. pS or pT treatment of SCC xenografts increased apoptotic cell death and decreased pro-survival P-Akt (S473) and Survivin, demonstrating the effectiveness of the peptides in vivo. These findings lay a framework for the further development of peptides to target 14-3-3ε-CDC25A interactions for skin cancer treatment.

Sex-specific differences in patients with nonmelanoma skin cancer of the pinna

Background

Generally, it is known that men are affected more frequently by nonmelanoma skin cancer (NMSC) than women. The aim of our study was to investigate the effect of sex on the characteristics of NMSCs of the pinna at the population that our center serves and to compare it with the international data.

Methods

We analyzed retrospectively the data of 225 patients with NMSC of the pinna. Sex‐specific differences were investigated for basal cell carcinoma (BCC) and cutaneous squamous cell carcinoma (cSCC) subgroups.

Results

The ratio of BCC to cSCC was determined in male patients at 1:1.3, in contrast in females it was identified at 4:1 (P = .001).

Conclusion

In our study, a new aspect of the sex‐dependent distribution of cSCC and BCC of the pinna was demonstrated. Women are affected four times more frequently by BCC than by cSCC, whereas in men this ratio is approximately equal.

An assessment of histological margins and recurrence of completely excised cutaneous SCC

There is a paucity of data relating to histological margins of cutaneous squamous cell carcinoma (cSCC) and local recurrence. Retrospective data were collected for 721 patients with cSCC treated at Queen Victoria Hospital, UK, and followed up for five years. The local recurrence rate was 6.1%, the mean time to recurrence was 12.61 months and 93% of recurrences occurred within two years. Sixty-six per cent of recurrences had a deep margin of 2.5 mm or less (p 0.041). The Pearson's correlation coefficient showed a strong correlation with tumour grade (r=0.82, p, 0.05), lymphovascular invasion (r=0.73. p<0.05), medium correlation with deep histological margin(r= -0.55, p<0.05), a weak correlation with male sex (r= 0.31, p<0.05) and the anatomical site of head and neck (r=0.31, p<0.05).The multiple regression analysis model using the 5 variables generated an r value of 0.71 and adjusted r square of 0.7. In conclusion, our findings are consistent with previously mentioned prognostic indicators and also demonstrate that deep histological margin is a significant predictor of local recurrence of cSCC. We recommend larger multi-institutional studies to confirm the above results to subsequently guide the specialist skin multidisciplinary teams' recommendations.

MicroRNA-186 promotes cell proliferation and inhibits cell apoptosis in cutaneous squamous cell carcinoma by targeting RETREG1

MicroRNAs (miRs), a class of small non-coding RNAs, have been demonstrated to be involved in the development and progression of human malignancies, including cutaneous squamous cell carcinoma (CSCC). miR-186 serves a suppressive role in certain common types of human cancer; however, its exact function in CSCC has not been reported previously. In the present study, the expression of miR-186 was significantly increased in CSCC tissues compared with adjacent non-tumour tissues. Overexpression of miR-186 significantly promoted CSCC cell proliferation while inhibiting cell apoptosis. Reticulophagy regulator 1 (RETREG1), a gene that is significantly downregulated in CSCC tissues and cell lines, was identified as a novel target of miR-186. In addition, the expression of RETREG1 was inversely correlated with miR-186 expression in CSCC tissues. Furthermore, the expression of RETREG1 was negatively regulated by miR-186 in CSCC cells, and restoration of RETREG1 attenuated the effects of miR-186 on CSCC cells. Taken together, the results of the current study suggest that miR-186 serves an oncogenic role in CSCC and may be used as a potential therapeutic target for the treatment of this disease.

miR-186 promotes tumor growth in cutaneous squamous cell carcinoma by inhibiting apoptotic protease activating factor-1

Cutaneous squamous cell carcinoma (cSCC) accounts for 20% of non-melanoma skin cancer worldwide. MicroRNAs (miRNAs or miRs) are a subtype of non-coding RNA associated with the progression of various types of human cancer. MiR-186 has been demonstrated to act as an oncogene in human tumors. However, the role of miR-186 in cSCC remains unclear. The expression of miR-186 and apoptotic protease activating factor 1 (APAF1) was examined using reverse transcription-quantitative polymerase chain reaction, western blotting and immunofluorescence. The correlation between miR-186 and APAF1 was determined using a dual-luciferase assay. Mimics or inhibitors of miR-186 were transfected into A-431 cells to establish cell lines with overexpressed or knocked-down miR-186, respectively. EdU staining and colony formation assays were performed to detect cell proliferation. Transwell and wound-healing assays were performed to analyze cell invasion and migration, respectively. Hoechst staining and flow cytometry were performed to assess cell apoptosis and cell cycle distribution. MiR-186 expression was significantly increased, while APAF1 expression was significantly decreased in cSCC tissues compared with the controls. An miR-186 binding site was predicted in APAF1 and their expression was negatively correlated in cSCC tissues. Cell proliferation, invasion and migration were significantly enhanced in the miR-186-overexpressed A-431 cells and attenuated in miR-186 knockdown cells compared with the control. APAF1 expression was regulated by miR-186, while APAF1 knockdown significantly promoted cell invasion and inhibited cell apoptosis. In summary, the results of the present study indicate that miR-186 serves as an oncogene in cSCC by inhibiting APAF1.

Cutaneous Squamous Cell Carcinoma With Sclerosing Features: An Uncommon and Potentially Aggressive Variant

Sclerosing squamous cell carcinoma (SCC), also known as "desmoplastic" SCC, is a rare subtype of cutaneous malignancy. This variant is clinically significant because it is associated with an increased risk of local recurrence and metastasis. We herein present 16 examples of sclerotic SCC of the skin in 8 men and 3 women, with a median age of 66 years. The most common site of origin for this tumor is the skin of the head and neck, including the scalp (5 tumors in 2 different patients), forehead (3 cases), nasal ala (2 cases), neck (2 cases in the same patient), ear (2 cases), cheek (1 case), and chest (1 case). Microscopically, sclerosing SCCs are characterized by cellular cords, nests, and islands, as well as scattered single cells infiltrating densely desmoplastic and collagenized connective tissue. The differential diagnosis principally includes sclerosing basal cell carcinoma, microcystic adnexal carcinoma, and desmoplastic trichoepithelioma. The main goals of this study are to further characterize these lesions pathologically, and increase general awareness of this SCC subtype.

Cutaneous Human Papillomavirus Infection and Development of Subsequent Squamous Cell Carcinoma of the Skin

The role of cutaneous human papillomavirus (HPV) infection in the development of subsequent cutaneous squamous cell carcinoma (SCC) is unknown. Pathologically confirmed cases of SCC (n = 150) enrolled in a previously conducted case-control study were included in a retrospective cohort study to examine the association of cutaneous HPV at the time of SCC diagnosis with the risk of subsequent SCC development. Data on HPV seropositivity, HPV DNA in eyebrow hairs (EB) and SCC tumors were available from the parent study. Incidence of subsequent SCC was estimated using person-years of follow up. Cox Proportional Hazards ratios were estimated to evaluate the associations of both, HPV seropositivity and HPV DNA positivity with subsequent SCC. The five year cumulative incidence of subsequent SCC was 72%. Seropositivity to cutaneous HPV was not associated with the risk of subsequent SCC (HR = 0.83, 95% CI = 0.41-1.67). Any beta HPV infection in EB was associated with reduced risk (HR = 0.30, 95% CI = 0.11-0.78) of subsequent SCC among cases who were positive for beta HPV DNA in tumor tissue. Infection with beta HPV type 2 (HR = 0.32, 95% CI = 0.12-0.86) in EB was associated with reduced risk of subsequent SCC among HPV DNA positive SCCs. In conclusion, beta HPV infection was inversely associated with the risk of subsequent SCC.

Cutaneous Squamous Cell Carcinoma: A Review of High-Risk and Metastatic Disease

Non-melanoma skin cancer represents one-third of all malignancies and its incidence is expected to rise until the year 2040. Cutaneous squamous cell carcinoma (cSCC) represents 20 % of all non-melanoma skin cancer and is a deadly threat owing to its ability to metastasize to any organ in the body. Therefore, a better understanding of cSCC is essential to strengthen preventative measures and curable treatment options. Currently, research demonstrates that cSCC is diagnosed at a rate of 15-35 per 100,000 people and is expected to increase 2-4 % per year. With respect to metastatic cSCC, this disease is more common in men; people over the age of 75 years; and inhabitants of the south and mid-west USA. In 2010, the American Joint Committee on Cancer updated the Cancer Staging Manual's primary tumor designation to now include high-risk factors; however, factors such as immunosuppression and tumor recurrence were not included. Other staging systems such as Brigham and Women's Hospital have allowed for increased stratification of cSCC. High-risk cSCC is defined as a cSCC that is staged as N0, extends beyond basement membrane, and has high-risk features associated with sub-clinical metastasis. High-risk features are depth of invasion (>2 mm), poor histological differentiation, high-risk anatomic location (face, ear, pre/post auricular, genitalia, hands, and feet), perineural involvement, recurrence, multiple cSCC tumors, and immunosuppression. Epidermal growth factor receptor and nuclear active IκB kinase (IKK) expression are also predictive of metastatic capabilities. Clinically, the initial lesions of a cSCC tumor can present as a painless plaque-like or verrucous tumor that can ultimately progress to being large, necrotic, and infected. Tumors can also present with paresthesias or lymphadenopathy depending on the location involved. With respect to prognosis, metastatic cSCC is lethal, with several large studies demonstrating a mortality rate of >70 %. Therefore, treatment of metastatic cSCC is difficult and depends on the location involved and extent of metastasis. Treatment options include surgery, radiation therapy, chemotherapy, and any combination of the above. Surgery alone can be used for metastatic cSCC treatment, but is not as effective as surgery in conjunction with radiation therapy. Radiation therapy has some success as a monotherapy in low-risk or cosmetically sensitive areas such as the external ear, eyelid or nose. According to the 2013 National Comprehensive Cancer Network Guidelines, cisplatin as a single agent or combined with 5-fluorouracil hold the strongest support for the treatment of metastatic cSCC; however, the supporting evidence is inconsistent and a curative chemotherapeutic approach is still lacking. Epidermal growth factor receptor inhibitors are a newer class of agents being used in metastatic cSCC and hold some promise as a therapy for this disease. Other areas of interest in finding curative treatments for metastatic cSCC include p53, hypermethylation of specific genes, chromatin remodeling genes, and the RAS/RTK/PI3K pathway. This review addresses the epidemiology, staging, risk factors, clinical presentation, management, and new trends in the treatment of high-risk and metastatic cSCC.