Comment
This case highlights the challenge in managing patients with high-risk cSCC, as the current guidelines provided by the American Joint Committee on Cancer (AJCC) and the National Comprehensive Cancer Network (NCCN) vary on the inclusion of intravascular involvement of cSCC as high risk and treatment is at the discretion of the provider in such circumstances.5-7 Both the AJCC and the NCCN have defined high-risk factors and staging for cSCC. The AJCC 8th edition (AJCC-8) revised guidelines include several high-risk factors of cSCC, including tumor diameter of 4 cm or larger leading to upstaging of a tumor from T2 to T3, invasion into or beyond the level of the subcutaneous tissue, depth of invasion greater than 6 mm, and large-caliber perineural invasion, and removed poorly differentiated histology from the AJCC-8 guidelines compared to the AJCC-7 guidelines. According to the AJCC-8 guidelines, location on the ear or lip, desmoplastic or spindle cell features, lymphovascular invasion, and immunosuppression do not affect tumor staging. The AJCC’s criteria for its TNM staging system strictly focus on features of the primary tumor and do not include clinical risk factors such as recurrence or immunosuppression. In contrast, the NCCN does include lymphovascular invasion as a high-risk factor of cSCC.
Intravascular invasion plays a considerable role in patient survival in certain cancers (eg, breast, gastric, prostate). In cutaneous malignancies, such as melanoma and SCC, metastasis more commonly occurs via lymphatic spread. When present, vascular invasion typically coexists with lymphatic involvement. The presence of microscopic lymphovascular invasion in cSCCs has not been definitively proven to increase the risk of metastases.8 However, multivariate analysis has shown that lymphovascular invasion independently predicts nodal metastasis and disease-specific death.9 As such, there are no guidelines on sentinel lymph node biopsy or adjuvant therapy in the setting of lymphovascular involvement of cSCCs. A survey-based study of 117 Mohs surgeons found a lack of consistency in their approaches to evaluation and management of high-risk SCCs. Most respondents noted perineural invasion and in-transit metastasis as the main findings that would lead to radiologic nodal staging, sentinel lymph node biopsy, or adjuvant radiotherapy, but they highlighted the lack of evidence-based treatment guidelines.4 High-risk cSCC can be treated via MMS or conventional surgery with safe excision margins. Adjuvant radiotherapy can reduce tumor recurrence and improve survival and therefore should be considered in cases of advanced or high-risk cSCCs, such as in our case.
The lack of consensus over the definition of high-risk cSCCs, a lack of high-quality therapeutic studies, and the absence of a prognostic model that integrates multiple risk factors all have made the prediction of outcomes and the formation of definitive management of cSCCs challenging. Multidisciplinary teams and vigilant monitoring are crucial in the successful management of high-risk cSCC, but further studies and reports are needed to develop definitive treatment algorithms.