The significance of regional metastasis location in head and neck cutaneous squamous cell carcinoma

Metastatic cutaneous squamous cell carcinoma accounts for nearly all squamous cell carcinomas of the parotid gland

Primary squamous cell carcinoma of the parotid gland (pSCCP) has long been recognized as a separate entity and is included in the WHO classifications of salivary gland tumors. However, it is widely accepted among head and neck pathologists that pSCCP is exceptionally rare. Yet, there are many publications describing series of pSCCP and data from SEER and other cancer register databases indicate erroneously an increasing incidence of pSCCP. Importantly, pSCCP and metastatic (secondary) squamous cell carcinoma to the parotid gland (mSCCP) have nearly identical histological features, and the diagnosis of pSCCP should only be made after the exclusion of mSCCP. Moreover, all of the histological diagnostic criteria proposed to be in favor of pSCCP (such as, for example, dysplasia of ductal epithelium) can be encountered in unequivocal mSCCP, thereby representing secondary growth along preexistent ducts. Squamous cell differentiation has also been reported in rare genetically defined primary parotid carcinomas, either as unequivocal histological squamous features (e.g., NUT carcinoma, mucoepidermoid carcinoma), by immunohistochemistry (e.g., in NUT carcinoma, adamantinoma-like Ewing sarcoma, basal-type salivary duct carcinoma, mucoepidermoid carcinoma), or a combination of both. Another major issue in this context is that the International Classification of Diseases (ICD) coding system does not distinguish between primary or metastatic disease, resulting in a large number of patients with mSCCP being misclassified as pSCCP. Immunohistochemistry and new molecular biomarkers have significantly improved the accuracy of the diagnosis of many salivary gland neoplasms, but until recently there were no biomarkers that can accurately distinguish between mSCCP and pSCCP. However, recent genomic profiling studies have unequivocally demonstrated that almost all SCCP analyzed to date have an ultraviolet light (UV)-induced mutational signature typical of mSCCP of skin origin. Thus, mutational signature analysis can be a very useful tool in determining the cutaneous origin of these tumors. Additional molecular studies may shed new light on this old diagnostic and clinical problem. This review presents a critical view of head and neck experts on this topic.

Surgical Management of Patients with Parotid Involvement from Non-Melanoma Skin Cancer of the Head and Neck

We conducted a retrospective, longitudinal study on a single-center series of patients who underwent parotidectomy in the management of advanced head and neck non-melanoma skin cancer (hnNMSC). The aim of this study was to identify prognostic factors associated with worse outcomes. Forty-one men and nine women were included. The mean age at the time of surgery was 78.9 years. The 5-year overall survival, disease-specific survival, locoregional recurrence-free survival, and distant metastasis-free survival calculated with Kaplan-Meier curves were 39.9%, 56.3%, 58.6%, and 82.1%, respectively. A univariate analysis showed that the status of the margins, facial nerve direct involvement, lymph vascular invasion, and histological grading were associated with worse outcomes (p < 0.05). Positive margins were associated with worse disease-specific survival also in a multivariate analysis (p = 0.001, HR = 32.02, and CIs 4.338 to 351.3). Because the resection in free margins is the most important prognostic factor, early diagnosis or, in the case of advanced disease, extensive surgical resection with concomitant reconstruction is needed. Adjuvant therapy is indicated in selected cases.

Primary and Secondary Tumors of the Parotid Gland: Clinical Features and Prognosis

Primary and secondary malignant tumors can affect the parotid gland. The aim of this retrospective study was to evaluate the clinical features and prognosis of malignant epithelial tumors of the parotid gland. In particular, a comparison between primary and secondary cancer and survival analyses were performed. Eighteen patients with primary cancer and fifteen with intraparotid metastasis from cutaneous squamous cell carcinoma were included. A chart review was performed to collect clinical data (age, sex, smoking, alcohol consumption, tumor stage, type of surgical procedure, complications, recurrence and death). The majority of primary tumors were early (T1-2 N0, 83%) with mucoepidermoid carcinoma being the most common (33%). Secondary tumors were mostly staged P2 (53%) and N0 (67%). Subjects with secondary tumors were older than those with primary cancer. Post-operative permanent facial palsy was observed in 5 patients (17%) with primary cancer and 9 (60%) with secondary tumors (p = 0.010). Two-year overall survival for primary and secondary parotid cancer was 76.58% and 43.51%, respectively (p = 0.048), while 2-year disease-free survival was 76.05% and 38.50%, respectively (p = 0.152). In conclusion, secondary cancer of the parotid gland has worse survival than primary tumors. In the future, the implementation of multimodality treatment of intraparotid metastases is necessary to improve oncologic outcomes.

Evolution of Head and Neck Cutaneous Squamous Cell Carcinoma Nodal Staging—An Australian Perspective

Simple Summary

Australia has the highest incidence of cutaneous squamous cell carcinoma of the head and neck (HNcSCC) in the world. Although the majority of HNcSCCs are cured by simple surgical excision, those that spread to lymph nodes require aggressive and debilitating surgery in conjunction with radiation therapy, with a significant risk of treatment failure and subsequent loss of life. Cancer staging is critical to guide prognosis, treatment (to maximise disease control and minimise morbidity), and for research. Australian institutions have been at the forefront of prognostication for HNcSCC with lymph node spread. Despite this, the search for a well performing staging system is ongoing. This review chronologically explores and summarises the Australian contribution to date and highlights the ongoing challenges.

Abstract

Cutaneous squamous cell carcinoma of the head and neck (HNcSCC) is one of the commonest malignancies. When patients present with regional metastatic disease, treatment escalation results in considerable morbidity and survival is markedly reduced. Owing to the high incidence, Australian institutions have been at the forefront of advocating for reliable, accurate, and clinically useful staging systems that recognise the distinct biological characteristics of HNcSCC. As a result, an extensive body of literature has been produced over the past two decades, which has defined critical prognostic factors, critiqued existing staging systems, and proposed alternative staging models. Notwithstanding, a suitable staging system has proved elusive. The goal of cancer staging is to group patients according to cancer characteristics for which survival differs between groups (distinctiveness), consistently decreases with increasing stage (monotonicity), and is similar within a group (homogeneity). Despite implementing major changes based on published data, the latest edition of the American Joint Committee on Cancer (AJCC) staging manual fails to satisfy these fundamental requirements. This review chronologically explores and summarises the Australian contribution to prognostication and nodal staging of HNcSCC and highlights the ongoing challenges.

Whole genome analysis reveals the genomic complexity in metastatic cutaneous squamous cell carcinoma

Metastatic cutaneous squamous cell carcinoma (CSCC) is a highly morbid disease requiring radical surgery and adjuvant therapy, which is associated with a poor prognosis. Yet, compared to other advanced malignancies, relatively little is known of the genomic landscape of metastatic CSCC. We have previously reported the mutational signatures and mutational patterns of CCCTC-binding factor (CTCF) regions in metastatic CSCC. However, many other genomic components (indel signatures, non-coding drivers, and structural variants) of metastatic CSCC have not been reported. To this end, we performed whole genome sequencing on lymph node metastases and blood DNA from 25 CSCC patients with regional metastases of the head and neck. We designed a multifaceted computational analysis at the whole genome level to provide a more comprehensive perspective of the genomic landscape of metastatic CSCC. In the non-coding genome, 3′ untranslated region (3′UTR) regions of EVC (48% of specimens), PPP1R1A (48% of specimens), and ABCA4 (20% of specimens) along with the tumor-suppressing long non-coding RNA (lncRNA) LINC01003 (64% of specimens) were significantly functionally altered (Q-value < 0.05) and represent potential non-coding biomarkers of CSCC. Recurrent copy number loss in the tumor suppressor gene PTPRD was observed. Gene amplification was much less frequent, and few genes were recurrently amplified. Single nucleotide variants driver analyses from three tools confirmed TP53 and CDKN2A as recurrently mutated genes but also identified C9 as a potential novel driver in this disease. Furthermore, indel signature analysis highlighted the dominance of ID signature 13 (ID13) followed by ID8 and ID9. ID9 has previously been shown to have no association with skin melanoma, unlike ID13 and ID8, suggesting a novel pattern of indel variation in metastatic CSCC. The enrichment analysis of various genetically altered candidates shows enrichment of “TGF-beta regulation of extracellular matrix” and “cell cycle G1 to S check points.” These enriched terms are associated with genetic instability, cell proliferation, and migration as mechanisms of genomic drivers of metastatic CSCC.