1. Indications for Mohs Surgery
Chrys Schmults, MD, MSCE
Christine Liang, MD

2. Overview
Brief review of Mohs technique and how it differs from standard excision
Review of data comparing outcomes with Mohs vs. standard excision
2010 NCCN guidelines
Cost-effectiveness of Mohs as compared to excision
Indications for Mohs
Too small
Too big
Just right
Enough to share (multidisciplinary approach)
Role of Mohs surgeon as cutaneous oncologist/care coordinator, especially for large and complex cases

3. What is Mohs surgery? Technique for removing skin cancer
Developed by Frederick Mohs, M.D. beginning in 1930’s
2 key features:
Nearly 100% of surgical margin is evaluated microscopically
The surgeon is also the pathologist
If another pathologist makes call on margin, it’s not Mohs and should not be billed as such

4. Mohs Surgery Advantage
All of peripheral & deep margin examined microscopically
Less than 1% is examined in standard vertical sections

5. Mohs Surgery Advantage

6. Mohs Surgery Procedure
Debulk visible tumor
Hatch marks made on skin for orientation

7. Mohs Surgery Procedure
Tumor excised with small (1mm - 2mm) border

8. Mohs surgery procedure
Tissue is placed on map preserving orientation
Tissue is inked
Locations and colors of ink replicated on map
Tissue inked
Corresponding Mohs map

9. Mohs Surgery Procedure
Tissue is frozen so it can be cut
in thin layers (frozen sections)

10. Mohs Surgery Procedure
Tissue pieces stained with hematoxylin and eosin

11. Mohs Surgery Procedure
Positive areas are recorded on the map

12. Mohs Surgery Procedure
Additional tissue is taken from positive areas

13. Mohs Surgery Procedure
Tissue is again inked, mapped, frozen, cut, and read by surgeon
Process repeated until margins are clear

14. Mohs Surgery Procedure
Wound is reconstructed so as to minimize scarring

15. Why is Mohs surgery used?
Highest reported cure rates (97-99% overall) for many types of skin cancer due to complete margin evaluation
Spares normal tissue so the wound is as small as possible while still fully removing cancer

16. Do we miss valuable information by not looking at entire tumor?
No. Clear margins are the crucial factor.
Used to look at debulk but stopped as almost never added information beyond the biopsy
Only evaluate debulk if
Diagnosis was in question
Biopsy location is in question
It is an unusual tumor (though looking at biopsy slides is usually sufficient to assess tumor appearance)
Mohs’ high cure rates have been established by looking only at the margins

17. Data comparing Mohs vs. excision and NCCN treatment guidelines regarding Mohs

18. BCC

19. Recurrence Rates for the Treatment of Primary Basal Cell Carcinoma
Rowe et al. J Dermatol Surg Oncol, 1989.

20. Summary of Recurrence Rates for Treatment of Recurrent BCC
Rowe et al. J Dermatol Surg Oncol, 1989.

21. RCT Mohs vs Excision of facial BCC 5 year local recurrence rate
Lesion
Mohs surgery
Excision
Primary BCC
n=408
2.5%
4.1%
Recurrent BCC
n=204
2.4%
12.1%
(p=0.01)
Mosterd et al, Lancet Oncol 2008

22. SCC

23. Mohs vs non-Mohs treatments in SCC 5 year local recurrence rate
Location
Mohs surgery
Non-Mohs treatment
Lip
2.3% (952)
10.5% (7022)
Ear
5.3% (337)
18.7% (214)
Recurrent SCC
10.0% (151)
23.3% (34)
(surgical excision)
From Rowe et al JAAD 1992

24. Overall cure rates for SCC: Mohs vs. non-Mohs treatments
Tumor factor
Mohs surgery
Non-Mohs treatments
Size > 2cm
75% (652)
58% (1205)
Poorly differentiated
67% (387)
46% (222)
From Rowe et al JAAD 1992

25. Treatment outcomes for perineural SCC (determinate cases)
Mohs surgery
Surgical excision
Local recurrence rate
0% (17)
47% (72)
Metastatic rate
8% (24)
47% (112)
**Surgical clearance of tumor is critical and may require head and
neck surgeon to pursue tumor into parotid or cranium
From Rowe et al JAAD 1992

26. 2010 NCCN treatment guidelines for BCC and SCC

27. 2010 NCCN Guidelines
Consensus category 2A –based on lower level evidence/NCCN uniform consensus

28. 2010 NCCN treatment guidelines
High risk BCC and SCC can only be treated with standard excision (using 1cm clinical margin) if:
it’s on trunk/extremities AND
diameter ≥2cm is only risk factor AND
it can be closed primarily
Otherwise, Mohs or complete circumferential peripheral and deep margin assessment with frozen or permanent sections (CCPDMA) is indicated

29. Use of Mohs in other tumors
Dermatofibroma sarcoma protuberans
Microcystic adnexal carcinoma
Extramammary paget’s disease
Atypical fibroxanthoma
Merkel cell carcinoma
Lentigo maligna, melanoma in situ
Standard of care for some tumors, controversial for others

30. Dermatofibromasarcoma protuberans
Study
Study Design
Results
Meguerditchian et al., 2010
Retrospective cohort
28 WLE (50 mo f/u)
20 Mohs (40 mo f/u)
Recurrence rate
-Wide local excision: 3.6%
-Mohs: 0% (p = 1.0)
Paradisi et al., 2008
38 WLE (4.8 yr f/u)
41 Mohs (5.4 yr f/u)
-Wide local excision: 13%
-Mohs: 0% (p = 0.015)
Gloster et al., 1996
39 WLE (36 mo f/u)
15 Mohs (40 mo f/u)
-Wide local excision: 12.8%
-Mohs: 6.6%
2010 study positive margins in 21% with WLE than mohs, but recurrence rates similar
NCCN treatment guidelines- excision with clear surgical margins, given significant subclinical extension – mohs, modified mohs, 30

31. Microcystic adnexal carcinoma
Study
Study Design
Results
Chiller, et al, 2000
Retrospective cohort
26 Excision
22 Mohs
Recurrence rate (3 yr mean f/u)
-Excision 1.5% pp/yr
-Mohs: 2.4% pp/yr
MMS exhibited a clear benefit over simple excision in that 30% of tumors treated with simple excision required at least another office visit
Leibovitch et al 2005
Prospective cohort
20 Mohs
Recurrence rate (5 yr f/u)
-Mohs: 5%
(Local recurrence rates of up to 30-47% have been reported with standard surgical excision)
MMS treatment of choice and is excellent for following the subclinical extension and tracing perineural involvement
The size of the defect can be up to 6 times the clinical appearance of the lesion1
In a series of 48 pts, MMS showed a clear benefit vs standard excision, with 30% of standard surgical excisions requiring at least another procedure to clear the margins4
Recurrence rates for standard excision range from 40-60%, compared to 0-12% after MMS
Some have suggested the use of an additional layer for permanents after complete clearance of margins with MMS for further histologic control, as frozen sections can be more difficult to interpret.5 No outcome data exist for this method 31

32. Extramammary Paget’s Disease
Study
Study Design
Results
Lee et al., 2008
Retrospective cohort
22 wide excision
11 Mohs
Recurrence rate (mean f/u 62 months)
-Wide excision: 36.4%
-Mohs: 18.2%
O’Connor et al,
38 WLE
41 Mohs
Recurrence rate
-Wide local excision: 22%
-Mohs: 8%
Study of 22 patients with EMPD retrospective study using radiotherapy, The 2- and 5-year local progression-free rates were 91% and 84%, respectively. Morbidity of the surgery is considerable, so radiotherapy may be highly considered. No comparison of radiotherapy to surgical treatment.
Recurrence with Mohs is still high and surgery can carry a very high morbidity in this disease
Superficial (electron beam) radiation warrants further study and has been used with success in our experience 32

33. Atypical fibroxanthoma
Study
Study Design
Results
Ang et al, 2009
Retrospective cohort
23 wide excision
59 Mohs
Recurrence rate
-Wide excision: 8% (8.7 yr)
-Mohs: 0% (4.5 yr f/u)
Treatment of choice in AFX 33

34. Merkel Cell Carcinoma Study Study Design Results O’Connor et al., 1997
Retrospective cohort
41 wide local excision
13 Mohs
Local recurrence rate
-Wide local excision: 31.7%
-Mohs: 8.3%
Regional metastasis rate
-Wide local excision: 48.8%
-Mohs: 33.3%
Boyer et al 2002
25 Mohs alone
20 Mohs +XRT
Mohs alone: 16% (28 mo f/u)
Mohs+XRT =0% (27 mo f/u)

35. Lentigo Maligna/MMIS Study Study Design Results Walling et al., 2007
Retrospective cohort
41 staged excision
16 Mohs
Recurrence rate
-Staged excision: 7.3% (mean f/u 95 months)
-Mohs: 33% (p < 0.025)
(mean f/u 117 months)
Bene et al., 2008
Prospective study
167 MIS pts
116 LM pts
Recurrence rate 1.8%
Frozen sections accurate 95.1% compared to paraffin sections
Controversy over the data for LM/MIS – no prospective RCTs, all data is single institution retrospective data.
Reliability of Interpretation of frozen sections an issue – rates vary depending on operator (Zitelli, coldiron >95% accuracy), vs 60-80% by other authors.
Recurrence rates following excisional surgery for MIS have
ranged from 6 to 20% in studies with a follow-up period of 3 years or more (Table 2). Mohs surgery offers significantly improved
recurrence rates of 0% to 3.6% over a minimum follow-up period of 18 months
Multiple studies showing that MART-1 staining helpful, now there is a 16 minute MART-1 that is effective. 35

36. Cost Considerations

37. Is Mohs cost-effective?
When something is more effective and cheaper/equivalent in price, it is superior
When something is both less effective and more expensive, it is inferior
If something is more effective but also more expensive, when is it cost-effective?
Available data indicate Mohs is more effective in curing non-melanoma skin cancer
Is it cost-effective?

38. Cost of Mohs vs. excision for 1cm tumor on cheek (2010 BWH Medicare professional + technical)
11643 (2-3cm excision) $249 + $664
13132 (Complex repair >2.5cm) $513 +$366
88305 (path) $154 +$311 (plus $176 + $310 for each immunostain if needed)
Total for excision: $2,257
Mohs:
99214 (Level 4 established) $82 (+ ? technical)
17311 (stage 1) $417 (+ ?$644 technical)
Total for Mohs: $2,022

39. Is Mohs cost-effective? YES!
When something is both more effective and cheaper/equivalent in price, it is superior
Mohs is in this category since reimbursement was cut 2 years ago

40. Indications for Mohs Too small (or too superficial)
Used to be lesions less than 2cm on trunk and proximal extremities
Now this is more case by case with cost equivalency
But the tumor should require surgery
Avoid biopsy of AK/SCCIS
Usually lie on a field of histologically similar damage
Hard to locate biopsy site
When is it “clear”?
Try cryotherapy (with light curettage) or topical 5FU
Biopsy and refer for surgery only if fails to clear with non-invasive treatment

41. Indications for Mohs Too big?
Extremely large tumors may require large excisions, bone removal, and reconstructions difficult to perform under local anesthesia
Still, we prefer to evaluate as we have experience in managing difficult tumors
assessing need for nodal staging, pre-op imaging, adjuvant therapy
coordination of multidisciplinary care via DFCI relationships and tumor board

42. Team Approach for Extensive Tumors
Recurrence after multiple standard excisions
Involvement of bone on CT
Mohs established peripheral margin to level of periosteum
Complete excision including bone performed by Head and Neck and Neurosurgery

43. Team Approach for Extensive Tumors
Recurrent SCC s/p excision and adjuvant XRT
MRI w/ bone involvement
Mohs for peripheral margin including periosteum
Neurosurgery removed bone
Head and neck reconstructed with free flap

44. Team Approach for Extensive Tumors
Mohs for peripheral margin including periosteum
Head and neck excised deep margin including bone
Patient opted for prosthesis

45. Indications for Mohs
In summary, no case is too big but some are too small
Please send us all invasive non-melanoma skin cancer (BCC, SCC, DFSP, AFX, MAC sebaceous carcinoma, etc.) meeting NCCN guidelines
On head, neck, hands, genitalia, below knees
2cm tumors on trunk/extremities
Deeper than dermis/4mm
Recurrent (including SCCIS that failed non-invasive treatment)
Moderate-poorly differentiated, infiltrative, micronodular, perineural/vascular/lymphatic invasion
Immunocompromised patient (CLL, RA, transplant)
Any others you don’t want to excise

46. Regarding Merkel
Though Mohs may be excellent in controlling primary tumors ≤2cm, SLN biopsy is standard care for almost all cases
This is currently difficult to coordinate at Faulkner

47. Regarding melanoma
We do not do Mohs on invasive melanoma (due to skip areas)
Happy to do wide excisions on melanomas that do not need SLN
No mitoses and <1mm
We currently do staged excision with en fasse margins for lentigo maligna and malignant melanoma in situ
May consider Mohs with MART1 in future

48. Staged excision “Slow Mohs” for lentigo maligna
Clear margin after 2 stages
Slow Mohs = staged excision
Use sutures or ink to orient tissue
Margins read by pathologist
Not closed until clear margins obtained
7 days after rotation flap

49. “Slow Mohs” for lentigo maligna
3 months post-op