Dermatology
Mohs Micrographic Surgery
Built from Dermatology, 5th Edition
What’s inside
18 sections · 105 slides
Overview
- What this topic covers
- 99%
Introduction and concept
What Mohs surgery is, and why checking the whole margin improves cure rates.
- What tissue-sparing means
- Four components of MMS
- Mohs sectioning versus standard bread-loaf sectioning
History
How Dr Frederic Mohs developed this technique and how it evolved into today's method.
- Origins of Mohs surgery
- Limits of the fixed-tissue method
- Move to the fresh-frozen technique
Training and appropriate use
How surgeons train for MMS, and the criteria that guide when it should be used.
- Training pathway
- Appropriate Use Criteria (AUC)
- Risk zones of the head and neck used in AUC
- Cost-effectiveness of MMS
- Current use in practice
Indications
Which skin cancers need Mohs surgery, based on tumor features, site, and patient history.
- Why complete margin exam matters
- Reading the indications table
- Indications for Mohs surgery in keratinocyte (non-melanoma) skin cancer
- Indications for Mohs surgery in keratinocyte (non-melanoma) skin cancer (continued)
- Tumors treated with MMS and their cure rates
- Cutaneous tumors treated with Mohs surgery and reported cure rates
- Cutaneous tumors treated with Mohs surgery and reported cure rates (continued)
Basal cell carcinoma
The most common skin cancer, and the best-studied indication for Mohs surgery.
- BCC cure rates
- Five-year cure rates for primary BCC and SCC by treatment modality
- High-risk BCC subtypes
Squamous cell carcinoma
SCC risk factors, high-risk anatomic sites, and related tumors on the SCC spectrum.
- Why MMS for SCC
- Recurrent squamous cell carcinoma of the ear
- Immunosuppression and rapid growth
- High-risk anatomic sites for SCC
- Erythroplasia of Queyrat
- Mohs technique notes for EQ
- Keratoacanthoma and verrucous carcinoma
Cutaneous melanoma
The role of Mohs surgery for melanoma in situ and its staged-excision variants.
- The lentigo maligna debate
- Why frozen sections are hard here
- Melan-A/MART-1 immunostaining of melanocytes
- Margins and recurrence data
- Improving margin accuracy
- Better immunostains for melanocytes
- Invasive melanoma
- Staged excisions ('slow Mohs')
- Staged excision techniques for melanoma
- Square technique in detail
- Geometric and spaghetti techniques
- Where the evidence stands
Uncommon and rare tumors
Less common cancers where MMS evidence relies mostly on case series rather than trials.
- Evidence base for rare tumors
- Atypical fibroxanthoma and pleomorphic dermal sarcoma
- Dermatofibrosarcoma protuberans (DFSP)
- Merkel cell carcinoma (MCC)
- Microcystic adnexal carcinoma (MAC)
- Recurrent BCC found to be a coexisting MAC
- Perineural invasion by three tumor types
- Sebaceous carcinoma
- Other adnexal and miscellaneous tumors
Contraindications
When Mohs surgery is not the right choice.
- When MMS may not be right
Preoperative assessment
What happens before the first surgical cut.
- History and consent
- Confirming the right site
- Preoperative imaging
- Complex, multidisciplinary cases
Technique
The step-by-step process, from first cut to tumor-free wound.
- Overview of the MMS visit
- Mohs micrographic surgery (MMS) flow sheet
- Mohs micrographic surgery (MMS) flow sheet (continued)
- The Mohs cycle, step by step
- Mohs surgery technique: excision and mapping
- Mohs surgery technique: re-excision and repair
Variations and refinements
Modifications that speed up processing or improve margin control for specific tumors.
- Single section method
- Non-beveled and wide-excision variants
- Rapid immunohistochemical (IHC) staining
- Strongly reactive immunostain highlighting duct-like structures
- Special and IHC stains used in MMS
- Special and immunohistochemical stains used in Mohs micrographic surgery
Challenges and pitfalls
Sources of error during MMS, and how surgeons and technicians work to avoid them.
- Two kinds of error
- Histopathologic look-alikes and pitfalls in Mohs surgery
- When to send tissue for permanent sections (1 of 2)
- When to send tissue for permanent sections (2 of 2)
- Collision tumor: BCC and SCC in the same site
- Tumors that invade bone
- Managing exposed bone
- Common pitfalls across the Mohs workflow
- Mohs micrographic surgery - challenges, pitfalls, and recommendations
- Mohs micrographic surgery - challenges, pitfalls, and recommendations (continued)
- Mohs micrographic surgery - challenges, pitfalls, and recommendations (continued)
- Mohs micrographic surgery - challenges, pitfalls, and recommendations (continued)
- Mohs micrographic surgery - challenges, pitfalls, and recommendations (continued)
- Perineural invasion on frozen versus formalin-fixed sections
- Artifacts causing false-negative and false-positive readings
Reconstruction
Rebuilding the wound once the tumor is confirmed gone.
- Planning the repair
Postoperative care and complications
Pain control, infection prevention, surveillance, and how safe MMS really is.
- Postoperative care
- How safe is MMS?
- Bleeding and medication risks
- Other complications
Future trends
Where Mohs surgery is heading next.
- What's next for MMS
- Key takeaways
References
Sources cited in this chapter.
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- References (continued)
- Dermatology, 5th Edition (2-Volume Set)