Can Squamous Cell Carcinoma In Situ (SCCIS) be sent for castle testing?

Castle Testing for Squamous Cell Carcinoma In Situ (SCCIS)

Squamous Cell Carcinoma In Situ (SCCIS) should not be sent for Castle testing, as Castle testing is not an appropriate or recommended diagnostic or management tool for SCCIS.

Understanding SCCIS and Appropriate Testing

SCCIS, also known as Bowen's disease, is a pre-invasive form of squamous cell carcinoma confined to the epidermis without dermal invasion. According to the British Association of Dermatologists' guidelines 1, the diagnosis and management of SCCIS involves:

• Histological confirmation through biopsy
• Assessment of lesion characteristics (size, location, thickness)
• Selection of appropriate treatment modality based on these characteristics

Diagnostic Approach for SCCIS

The standard diagnostic approach for SCCIS includes:

1. Clinical examination - Identifying suspicious lesions (indurated, nodular, keratinizing or crusted tumors)
2. Biopsy - Establishing histological diagnosis
3. Histopathological assessment - Confirming in-situ nature without dermal invasion

The guidelines do not mention Castle testing as part of the diagnostic or management algorithm for SCCIS 1.

Why Castle Testing Is Not Appropriate for SCCIS

Castle testing (Castle Biosciences) typically refers to gene expression profiling tests used primarily for:

1. Uveal melanoma prognostication
2. Cutaneous melanoma risk assessment
3. Certain other specific cancer types

These molecular tests are designed to provide prognostic information for specific cancer types, but they are not validated or recommended for SCCIS management according to current guidelines 1.

Recommended Management Approaches for SCCIS

The British Association of Dermatologists provides clear treatment recommendations for SCCIS based on lesion characteristics 1:

For small, single/few lesions in good healing sites:

• 5-Fluorouracil
• Imiquimod
• Cryotherapy
• Curettage with cautery
• Excision
• Photodynamic therapy (PDT)

For large or multiple lesions:

• PDT (particularly effective)
• Topical treatments (5-FU, imiquimod)
• Surgical approaches for selected cases

For challenging locations (lower leg, digital, facial):

• Treatment selection should consider healing potential and functional outcomes
• PDT may be preferred for lower leg lesions
• Mohs micrographic surgery for tissue-sparing in digital or facial lesions

Treatment Efficacy Comparison

Recent meta-analysis evidence shows that 2:

• Electrodessication with curettage has a low recurrence rate (2.0%)
• Cryotherapy with curettage also shows low recurrence (1.6%)
• Higher recurrence rates are seen with PDT (29.0%), 5-fluorouracil (26.6%), and imiquimod (16.1%)

Common Pitfalls in SCCIS Management

1. Misdiagnosis: Failing to distinguish SCCIS from invasive SCC or other conditions
2. Inappropriate treatment selection: Not considering site-specific healing challenges
3. Inadequate follow-up: Missing progression to invasive disease
4. Unnecessary testing: Ordering molecular tests like Castle testing that are not indicated for SCCIS

Conclusion

For SCCIS, the appropriate approach is histological diagnosis followed by selection of treatment based on lesion characteristics, location, and patient factors. Castle testing is not part of the standard management algorithm for SCCIS according to current guidelines and evidence.