- Overview: What "11 Domains" Actually Means
- Domain 1: Tumor Biology and Cutaneous Oncology
- Domain 2: Indications for MMS
- Domain 3: Surgical Technique
- Domain 4: Surgical Anatomy
- Domain 5: Local and Regional Anesthesia
- Domain 6: Preoperative Evaluation
- Domain 7: Histological Technique
- Domain 8: Wound Care and Wound Healing
- Domain 9: Dermatopathology
- Domain 10: Surgical Complications
- Domain 11: Instrumentation
- How the Domains Map to Exam Format
- A Domain-by-Domain Study Schedule
- FAQ
- AOBD's written exam coverage spans 11 editorial topic areas, from tumor biology to instrumentation.
- The written component is 110 multiple-choice questions in two hours - not the separate 100-question Mohs OCC exam.
- No official percentage weights exist per domain; any allocation you see in practice materials is editorial, not published.
- Passing requires a scaled score of at least 500 on AOBD's 200-800 scale.
Overview: What "11 Domains" Actually Means
Candidates preparing for the AOBD Subspecialty Certification in Mohs Micrographic Surgery (MMS) exam often search for a fixed "blueprint" with percentage weights per topic, similar to what other certifying boards publish. AOBD does not publish that kind of breakdown. Instead, its official materials list a set of content examples that the written exam draws from - tumor biology and cutaneous oncology, indications and technique, anatomy, anesthesia, preoperative evaluation, histological technique, wound care, dermatopathology, complications, and instrumentation.
This guide organizes those official examples into 11 distinct study domains so you can build a structured review plan. Treat this as an editorial framework for preparation - not an official domain count or a guaranteed item distribution on your specific 110-question form. For a broader walkthrough of the entire certification pathway, see our MMS Study Guide 2026: How to Pass on Your First Attempt.
Domain 1: Tumor Biology and Cutaneous Oncology
Tumor Biology and Cutaneous Oncology
This domain covers how basal cell carcinoma, squamous cell carcinoma, and other cutaneous malignancies behave biologically - growth patterns, subclinical extension, perineural invasion, and factors that predict recurrence.
- Aggressive vs. indolent histologic subtypes and their implications for margin planning
- Risk stratification for recurrence based on tumor size, location, and prior treatment
- Rare tumor types occasionally treated with Mohs (dermatofibrosarcoma protuberans, microcystic adnexal carcinoma, extramammary Paget disease)
Because tumor behavior drives every downstream decision - whether to offer Mohs, how many stages to expect, how to counsel a patient - this domain sits conceptually upstream of nearly everything else on the exam.
Domain 2: Indications for MMS
Indications for MMS
Knowing when Mohs is the appropriate modality - versus standard excision, curettage, or radiation - is tested through scenario-based questions describing tumor characteristics, anatomic location, and patient factors.
- Appropriate Use Criteria concepts applied to high-risk anatomic zones (H-zone of the face, genitalia, digits)
- Recurrent tumors and prior radiation as indications
- Special populations: immunosuppressed patients, genetic syndromes with multiple skin cancers
Expect vignette-style items rather than pure recall. This is a hallmark of AOBD's written format - clinical scenarios that require you to apply indication criteria, not just memorize a list.
Domain 3: Surgical Technique
Surgical technique questions test the mechanics of the Mohs process itself: mapping, debulking, tissue orientation, and the stage-by-stage decision logic that separates Mohs from standard excisional surgery.
Surgical Technique
- Debulking versus saucerization technique selection
- Accurate tissue mapping and orientation for pathology correlation
- Decision-making when margins are positive on subsequent stages
- Repair timing and staged reconstruction planning
Domain 4: Surgical Anatomy
Surgical anatomy is heavily represented in candidate discussions of the exam because facial danger zones carry outsized clinical consequences. Expect detailed questions on nerve courses, vascular territories, and tissue planes relevant to Mohs defects.
Surgical Anatomy
- Facial nerve branches and their surface landmarks
- Danger zones: temporal branch, marginal mandibular branch, spinal accessory nerve
- Layered anatomy of the scalp, eyelid, ear, and nose relevant to reconstruction
Domain 5: Local and Regional Anesthesia
This domain covers anesthetic agents, dosing limits, nerve blocks used in facial and extremity Mohs cases, and management of complications like toxicity or vasovagal response.
Local and Regional Anesthesia
- Maximum safe dosing of lidocaine with and without epinephrine
- Regional nerve blocks for the face, ear, and digits
- Recognizing and managing local anesthetic systemic toxicity
Domain 6: Preoperative Evaluation
Preoperative evaluation questions test judgment around anticoagulation management, informed consent, comorbidity screening, and patient selection before the first stage begins.
Preoperative Evaluation
- Anticoagulant and antiplatelet management before Mohs surgery
- Antibiotic prophylaxis indications (cardiac, prosthetic joint)
- Informed consent elements specific to staged excision
Domain 7: Histological Technique
Histological technique bridges the surgical and pathology sides of Mohs practice. This is one of the domains that most distinguishes MMS certification from general dermatology board content, since it tests frozen-section processing specific to the Mohs lab.
Histological Technique
- Frozen section preparation and embedding for complete margin assessment
- Common staining protocols (H&E, toluidine blue) and when each is used
- Artifacts that mimic residual tumor and how to identify them
Domain 8: Wound Care and Wound Healing
This domain covers the biology of second-intention healing, dressing selection, and postoperative wound management across different anatomic sites and defect types.
Wound Care and Wound Healing
- Phases of wound healing and factors that impair them
- Second-intention healing candidacy by anatomic location
- Dressing selection for exposed cartilage, bone, or tendon
Domain 9: Dermatopathology
Dermatopathology overlaps with histological technique but focuses more on interpreting the slide itself - distinguishing tumor from normal adnexal structures, scar, and inflammation under frozen-section conditions.
Dermatopathology
- Differentiating basaloid tumor nests from normal follicular epithelium
- Recognizing perineural invasion on frozen sections
- Distinguishing recurrent tumor from scar-related changes
Domain 10: Surgical Complications
Complications questions test recognition and management of bleeding, infection, nerve injury, and flap or graft compromise in the immediate and delayed postoperative period.
Surgical Complications
- Hematoma recognition and evacuation timing
- Signs of flap or graft failure and salvage options
- Postoperative infection versus expected inflammatory changes
Domain 11: Instrumentation
Instrumentation rounds out the written coverage examples with knowledge of the tools used throughout the Mohs process - from tissue processing equipment to the surgical instruments used in excision and repair.
Instrumentation
- Cryostat setup and troubleshooting for frozen sections
- Electrosurgical units and settings for hemostasis
- Instrument selection for delicate facial reconstruction
How the Domains Map to Exam Format
Understanding domain content is only half the picture - you also need to understand how AOBD tests it. The written component is 110 multiple-choice questions in two hours, which averages to just over one minute per question. That pace rewards candidates who have internalized concepts well enough to recognize the correct answer quickly rather than reasoning through unfamiliar material during the exam itself.
The written component sits alongside a practical component: six submitted representative cases, with an oral explanation required if AOBD requests one. If you fail to submit qualifying practical cases, you cannot sit for the written component at all - the two are sequentially linked, not independent hurdles. If a practical retake becomes necessary, AOBD requires three new cases, so case selection and documentation should be treated as seriously as content review. For a full breakdown of scoring mechanics, read MMS Passing Score 2026: Exactly What You Need to Pass, and for the underlying eligibility routes, see MMS Requirements 2026: Eligibility, Prerequisites & How to Qualify.
| Component | Format | Key Detail |
|---|---|---|
| Written exam | 110 multiple-choice questions | Two-hour time limit; covers all 11 domains |
| Practical component | Six submitted cases | Oral explanation possible if requested; retake needs three new cases |
| Passing standard | Scaled score | At least 500 on a 200-800 scale |
| Mohs OCC exam (separate) | 100 questions | Maintenance context, not the initial certification exam |
Key Takeaway
Submit and finalize your six practical cases well before your target written exam date - a missing or rejected case set blocks written exam eligibility entirely, regardless of how well you know the 11 domains.
A Domain-by-Domain Study Schedule
Generic study methods like spaced repetition and timed review blocks only help if they're anchored to MMS-specific content. Below is one way to sequence the 11 domains across a compressed review window, front-loading topics that require the most conceptual layering before moving into interpretation-heavy domains.
Foundations
- Domain 1: Tumor Biology and Cutaneous Oncology
- Domain 2: Indications for MMS
Surgical Core
- Domain 3: Surgical Technique
- Domain 4: Surgical Anatomy
Perioperative Management
- Domain 5: Local and Regional Anesthesia
- Domain 6: Preoperative Evaluation
Lab and Pathology
- Domain 7: Histological Technique
- Domain 9: Dermatopathology
Postoperative and Tools
- Domain 8: Wound Care and Wound Healing
- Domain 10: Surgical Complications
- Domain 11: Instrumentation
Timed Practice
- Full-length timed sets under two-hour, 110-question conditions
- Review missed items by domain, not by test number
Run timed practice sets that mirror the real 110-question, two-hour format at the main practice test platform, then review each missed question by domain rather than by the order it appeared. This exposes weak domains faster than reviewing tests linearly. If you're deciding how much lead time you need overall, our piece on How Hard Is the MMS Exam? Complete Difficulty Guide 2026 walks through pacing considerations in more depth.
Who Actually Tests on These Domains
These 11 domains aren't abstract - they reflect what a solo or group-practice Mohs surgeon needs day to day. Practices hiring board-certified Mohs surgeons expect fluency in anatomy-driven surgical planning (Domains 3 and 4), lab-based margin assessment (Domains 7 and 9), and complication management (Domain 10) because these are the areas where clinical judgment directly affects patient outcomes and practice liability. If you're weighing whether the credential translates into career opportunity, see MMS Jobs and Is the MMS Certification Worth It? Complete ROI Analysis 2026 for context beyond the exam itself.
Registration and Fee Details That Affect Your Prep Timeline
Domain mastery only matters if you're actually seated for the exam on the right date with the right documentation. The 2026 exam date is September 24, with a June 24 first application deadline and July 24 final deadline. Published fees are USD 1,800 for the initial attempt, USD 900 for a one-component retake, USD 1,800 for a both-component retake, and USD 540 for late applications. Build your domain review calendar backward from the July 24 final deadline, not the September exam date, since incomplete case documentation or eligibility paperwork submitted late can cost you the entire cycle. For the full fee table and budgeting guidance, see MMS Certification Cost 2026: Complete Pricing Breakdown, and for the complete scheduling calendar, see MMS Exam Dates 2026: Testing Windows, Deadlines & Scheduling.
FAQ
No. AOBD publishes a list of content examples covering tumor biology, indications, technique, anatomy, anesthesia, preoperative evaluation, histological technique, wound care, dermatopathology, complications, and instrumentation. This guide organizes those examples into 11 domains for study purposes; it is not an official domain count with published weights.
The initial written component has 110 multiple-choice questions administered in two hours. The Mohs OCC exam, used for maintenance of certification rather than initial certification, has 100 questions. Keep these two separate when researching format details.
The practical component evaluates six submitted representative cases, with oral explanation if AOBD requests it, focusing on real-world application of technique, histology, and case management rather than testing each written domain discretely. Missing or incomplete practical cases prevents you from taking the written component at all.
AOBD's published passing standard is a scaled score of at least 500 on a 200-800 scale for the written component. There is no published minimum per individual domain, so overall performance across the 11 topic areas is what matters.
There's no published weighting to justify skipping any domain, but Domains 3, 4, 7, and 9 (surgical technique, surgical anatomy, histological technique, and dermatopathology) tend to require the most layered conceptual understanding and are worth extra timed-practice review. See our MMS Cheat Sheet 2026: One-Page Review of Must-Know Facts for a condensed reference.