Cutaneous squamous cell carcinoma: a comprehensive clinicopathologic classification. Part one.

Area of Science:

• Dermatopathology
• Oncology

Background:

• Cutaneous squamous cell carcinoma (SCC) exhibits diverse clinical behaviors, from indolent to aggressive with metastatic potential.
• Current classification often treats all SCCs generically, lacking a system to differentiate aggressiveness.
• A definitive clinicopathological system for categorizing SCC based on malignant potential is needed.

Purpose of the Study:

• To propose a novel clinicopathological classification system for cutaneous SCC based on risk stratification.
• To categorize SCC variants into low, intermediate, high, and indeterminate risk groups according to their metastatic potential.

Main Methods:

• Categorization of SCC subtypes based on established or estimated metastatic rates.
• Grouping includes low (< or = 2%), intermediate (3-10%), high (>10%), and indeterminate risk categories.
• Identification of specific SCC variants within each risk category.

Main Results:

• Low-risk SCCs: actinic keratosis-associated, HPV-associated, tricholemmal carcinoma, spindle cell SCC (non-radiation).
• Intermediate-risk SCCs: adenoid SCC, intraepidermal epithelioma with invasion, lymphoepithelioma-like carcinoma.
• High-risk SCCs: de novo SCC, SCC with predisposing factors (radiation, scars, immunosuppression), invasive Bowen's disease, adenosquamous carcinoma, malignant proliferating pilar tumors.
• Indeterminate category: signet ring cell SCC, follicular SCC, papillary SCC, SCC in adnexal cysts, squamoid eccrine ductal carcinoma, clear-cell SCC.

Conclusions:

• Subclassification of cutaneous SCC into risk-based categories is crucial for prognostication.
• Integrating risk stratification with factors like tumor size, differentiation, depth, and perineural invasion optimizes patient management.
• This system provides prognostically relevant information to guide optimal treatment strategies for cutaneous SCC.