Superficially Invasive Squamous Cell Carcinoma: Aggressiveness Assessment
Superficially invasive squamous cell carcinoma (SISCCA) is considered a non-aggressive form of squamous cell carcinoma with low metastatic potential. 1
Definition and Classification
- SISCCA is defined as anal cancer that has been completely excised, with ≤3-mm basement membrane invasion and a maximal horizontal spread of ≤7 mm (T1, NX) 1
- It is typically found incidentally during biopsy or excision of what was thought to be a benign lesion such as a condyloma, hemorrhoid, or anal skin tag 1
- SISCCA falls into the low-risk category of squamous cell carcinomas, with a metastatic rate of ≤2% 2
Risk Assessment
Low-Risk Features of SISCCA
- Superficial invasion (≤3mm depth) 1
- Limited horizontal spread (≤7mm) 1
- Well-differentiated histology 1
- No perineural involvement 1
- No lymphovascular invasion 3
Factors That Would Increase Risk
While SISCCA itself is non-aggressive, certain factors would increase the risk profile:
- Perineural involvement (significantly increases risk of recurrence and metastasis) 1
- Poor differentiation (associated with worse outcomes) 1
- Desmoplastic features (associated with increased risk of recurrence and metastasis) 1
- Invasion into deep reticular dermis or subcutaneous fat 1
- Immunosuppression (particularly HIV infection can lead to more aggressive behavior) 4
- Location in high-risk anatomic sites 5
Management Implications
- For SISCCA with histologically negative margins in carefully selected patients, local excision alone with a structured surveillance plan may represent adequate treatment 1
- A careful surveillance plan is necessary as observational studies have reported detection of high-grade squamous intraepithelial lesions in 74% of patients after local excision 1
- For lesions with higher risk features, more aggressive treatment approaches may be warranted 3, 5
Clinical Outcomes
- A retrospective study of patients with completely excised invasive anal cancer, including those meeting criteria for superficially invasive disease, showed excellent outcomes with 5-year overall survival of 100% and 5-year cancer recurrence-free survival rates of 87% 1
- This supports the classification of SISCCA as a non-aggressive variant of squamous cell carcinoma 1, 2
Important Considerations
- Although the risk of metastasis from SISCCA is negligible, the risk of recurrence depends on the presence or absence of additional risk factors 1
- Regular follow-up is essential as these lesions can recur locally 1
- The NCCN guidelines specifically categorize superficial basal cell carcinoma as non-aggressive, and the same principle applies to superficially invasive SCC 1