From the Guidelines
Surgical excision with 1- to 2-cm margins to the investing fascial layer is the standard technique for Merkel cell carcinoma. This approach is based on the recommendation from the Journal of the National Comprehensive Cancer Network, which emphasizes the importance of complete extirpation of the tumor at initial resection to achieve clear surgical margins when clinically feasible 1. The margins for Merkel cell carcinoma are as follows:
- 1- to 2-cm margins to the investing fascial layer for wide local excision
- Consideration of Mohs surgery, modified Mohs surgery, or complete circumferential peripheral and deep-margin assessment (CCPDMA) for tissue sparing, especially for facial MCC 1
- The depth of excision should extend to the fascia to ensure complete removal of the tumor
- Primary tumors should be excised with 1 cm margins for lesions less than 2 cm in size, and 2 cm margins for larger tumors The aggressive nature of Merkel cell carcinoma justifies these wider margins compared to other skin cancers, as the tumor has a tendency for dermal lymphatic invasion and spread 1. Complete surgical excision with appropriate margins remains the cornerstone of treatment for the primary tumor. It is also important to note that adjuvant radiation therapy should not be significantly delayed in pursuit of clear surgical margins, as preradiation margin status has been found to have no impact on time to locoregional failure 1.
From the Research
Margins for Merkel Cell Carcinoma
- The size of surgical margins for Merkel cell carcinoma (MCC) is a topic of debate, with various studies suggesting different margin sizes.
- A study published in 2021 in the Journal of the American Academy of Dermatology found that narrow excision margins (≤1.0 cm) were appropriate for MCC when combined with adjuvant radiation therapy, with a local recurrence rate of 1% 2.
- Another study published in 2025 in Dermatology and Therapy found that obtaining negative surgical margins was associated with enhanced overall survival, regardless of the type of surgery used (excision margin <1 cm, ≥1 cm, or Mohs micrographic surgery) 3.
- A study published in 2016 in the Journal of the National Cancer Institute found that adjuvant radiation therapy was associated with improved overall survival in stages I-II MCC, but not in stage III MCC 4.
- A study published in 2007 in the Journal of the American Academy of Dermatology suggested that adjuvant radiation therapy may be indicated for many MCC patients, while adjuvant chemotherapy should largely be restricted to clinical trials 5.
- A study published in 2021 in JAMA Dermatology found that local excision margins larger than 1.0 cm were associated with improvements in overall survival, regardless of tumor subsite or receipt of adjuvant radiotherapy 6.
Key Findings
- Narrow excision margins (≤1.0 cm) may be sufficient for MCC when combined with adjuvant radiation therapy 2.
- Obtaining negative surgical margins is associated with enhanced overall survival 3.
- Adjuvant radiation therapy is associated with improved overall survival in stages I-II MCC 4.
- Adjuvant chemotherapy is not well supported for MCC treatment 5.
- Local excision margins larger than 1.0 cm are associated with improvements in overall survival 6.