Advanced Cutaneous Squamous Cell Carcinoma Extending to the Temporal Bone

Introduction: Primary temporal bone tumors are rare and aggressive, with an estimated incidence of 1–6 cases per 1 million population. However, cutaneous malignancies extending to the temporal bone, particularly squamous cell carcinomas (SCC), are a problem that deserves more attention. These tumors can be as difficult to manage and are often quoted to be more common than the primary subtype around the world. This certainly holds true in regions such as Queensland (Australia) and southern United States, where nonmelanoma skin cancer (NMSC) rates are extraordinarily high. Yet, a greater paucity of evidence exists on cutaneous malignancy involving the temporal bone, with very few series exclusively examining this specific disease entity. Thus, staging systems, treatment protocols, survival data, and prognostic factors, which are often applied interchangeably for all temporal bone tumors regardless of origin, may be unreliable and not entirely applicable for cutaneous malignancy extending to the temporal bone.

Objective: To evaluate the epidemiology, patterns of spread, survival outcomes, and prognostic factors of patients with advanced periauricular cutaneous SCC extending to the temporal bone managed with temporal bone resection.

To develop a unique staging system for preauricular cutaneous SCC extending to the temporal bone, leading to more accurate prognostication and standardized operative recommendations.

Methods: This is a multi-institutional retrospective study of 150 patients* who underwent temporal bone resection for advanced periauricular cutaneous SCC at 2 tertiary care centers between 2000 and 2019. Data were collected on demographics, disease extent, treatment, histopathology, and survival outcome. All patients were staged according to the modified Pittsburgh Staging System (mPSS) and AJCC 8th edition TNM Staging System. Kaplan–Meier survival analysis was performed, and prognostic factors were identified through uni- and multivariate analysis.

A human cadaveric dissection series was conducted to identify potential fascial planes of dissection and barriers of spread in relation to advanced preauricular cutaneous malignancies. Relevant planes were mapped on cross-sectional imaging and correlated with survival outcomes. These findings, together with other prognostic factors identified, were used to formulate a novel staging system. The predictive accuracy of this staging system was compared with the mPSS and AJCC systems.

Results: This is the largest ever case series of cutaneous SCC extending to the temporal bone. Data collection is being finalized and analysis will be completed before the end of 2019.

The most cranial part of the carotid sheath, specifically the tensor-vascular styloid fascia, is an important barrier to medial spread of disease, and could be a useful plane of dissection in extirpative surgery (see picture as example of dissection).

Conclusion: Conclusions will be drawn once data analysis is complete.

*Final patient numbers TBD but will be at least 150.

Fig. 1

No conflict of interest has been declared by the author(s).