Guidelines of Care for Mohs Micrographic Surgery
© American Academy of Dermatology Association, 2003 all rights reserved.
Guidelines/Outcomes Committee: Lynn A. Drake, MD, Chairman, Scott M.Dinehart,
MD, Robert W. Goltz, MD, Gloria F. Graham, MD, Maria K. Hordinsky, MD, Charles W.
Lewis, MD, David M. Pariser, MD, Stuart J. Salasche, MD, John W. Skouge, MD, Maria
L. Chanco Turner, MD, Stephen B.
Webster, MD, Duane C. Whitaker, MD, Barbara
Butler, CPA-SDR Consultant, and Barbara J. Lowery, MPH .Task Force on Mohs
Micrographic Surgery: Hubert T. Greenway, MD, Chairman, William L. Dobes, MD, Matthew
M. Goodman, MD, Stephen H. Mandy, MD, and Stuart J. Salasche, MD
Guidelines of Care for Mohs Micrographic Surgery
This report reflects the best data available at the time the report was prepared, but caution should be
exercised in interpreting the data; the results of future studies may require alteration of the conclusions or
recommendations set forth in this report.Copyright© 1995 by the American Academy of Dermatology
Guidelines of care for Mohs micrographic surgery
I. Introduction
The American Academy of Dermatology’s Guidelines/Outcomes Committee is developing
guidelines of care for our profession. The development of guidelines will promote the continued delivery
of quality care and assist those outside our profession in understanding the complexities and scope of care
provided by dermatologists. For the benefit of members of the American Academy of Dermatology who
practice in countries outside the jurisdiction of the United States, the listed treatments may include
agents that are not currently approved by the U.S. Food and Drug Administration.
II. Definition
Mohs micrographic surgery (MMS) is a surgical methods for the removal of
tissue including certain cutaneous neoplasms (see Section V.A.2.e.1 for
description of technique). It is characterized by precise margin control
that allows complete examination of all margins of tissue removed. The
technique has high potential for cure with maximal preservation of normal
tissue. The Mohs surgeon normally acts in two integrated, but separate and
distinct, capacities: surgeon and pathologist. If either of these
responsibilities is delegated to another physician who reports his or her
services separately, this is a variation from the traditional definition
of MMS. The current official name is Mohs micrographic surgery and will be
used in these guidelines. Originally designated as chemosurgery because
the tissues were chemically fixed in situ before excision, the name
eventually came to be synonymous with microscopically controlled surgery.
Many synonyms survive, including chemosurgery, fixed tissue technique,
fresh tissue technique, microscopically controlled surgery, Mohs
histographic surgery, Mohs technique, Mohs surgery.
III. Rationale
A. Scope
MMS is a surgical technique for the removal of both common and unusual tumors of the skin
and mucous membranes and is utilized by physicians with special expertise. The goal of MMS is complete
tumor removal with maximal preservation of normal tissue. Basal cell carcinomas and squamous cell
carcinomas are the two most common neoplasms for which MMS is utilized.
B. Issue
There are multiple well-accepted surgical and non-surgical approaches for the treatment of
cutaneous neoplasms and skin cancers. Certain tumors, by virtue of their characteristics (see
"Indications"), may require a more precise level of treatment. MMS offers high cure rates for malignant
skin tumors with maximum preservation of surrounding normal tissue. Several considerations pertaining
to the feasibility and relevance of MMS include evaluation of each of the lesions being treated, the history
associated with the lesion(s), general medical history, risk factors, and other individual patient
considerations. MMS is not indicated in the treatment of all skin tumors. This document presents the
factors that are relevant to and the indications for utilization of MMS for the treatment of skin tumors.
IV. Diagnostic criteria
A. Clinical
1. History
a. General medical history may include the following:
1) Previous surgeries and hospitalizations
2) Skin cancer history and treatment
3) Relevant family and social history (e.g., lives alone, ability to care
for self)
4) Known allergies
5) Current medications
6) Systemic illness
7) nfectious or immunosuppressive disease
8) Documentation of vascular disease, prosthetic joints, or valves
requiring antibiotic prophylaxis
9) History of bleeding disorders
10) Other
b. History related to the tumor or lesion may include the following
1) Duration
2) Rate of growth
3) Previous treatment
4) Characteristics related to the specific diagnosis (e.g., trauma,
development in a preexisting lesion)
5) Risk factors associated with the cause (e.g., sun exposure, previous
radiation therapy)
6) Risk factors associated with aggressive biologic behavior, increased
incidence of local recurrence or metastases
7) Other
2. Physical examination
a. General physical examination as appropriate
b. Examination and clinical evaluation of the tumor may include the
following:
1) Size
2) Ulceration
3) Color
4) Location
5) Induration
6) Invasion into deeper tissues
7) Associated scar or changes from previous treatment
8) Relation to the surrounding normal structures
9) Documentation of lesion location by photographs, drawings, or
description
10) Other clinical characteristics
c. Examination of areas of lymphatic drainage when indicated. The clinical
presence of lymphadenopathy may necessitate exclusion of metastatic
disease.
d. Regional or total body skin examination when indicated
3. Indications
MMS is indicated as appropriate therapy for some cutaneous carcinomas and
neoplasms that have the following characteristics:
a. Basal cell carcinoma (BCC)
1) High risk for local recurrence
a) Ill-defined clinical borders
b) Anatomic sites in which other types of treatment result in a higher
potential risk of recurrence
(1) Periorbital and canthal regions
(2) Central third of the face
(3) Columella
(4) Periauricular-tragal
(5) Postauricular sulcus
(6) Perioral
(7) Nasofacial sulcus and perinasal
c) History of incomplete removal
d) History of previous irradiation therapy
e) History of recurrence
f) Large size
g) Histologic pattern
(1) Morpheaform
(2) Keratinizing
(3) Metatypical
(4) Infiltrating
(5) Contiguous tumors (i.e., BCC and squamous cell carcinomas)
(6) Multicentric
(7) Deep tissue or bone involvement
(8) Perineural or perivascular involvement
h) Other
2) Areas of important tissue preservation
a) Nasal tip and alae
b) Lips, cutaneous and vermilion
c) Eyelids
d) Auricular helix and canal
e) Hands and feet
f) Genitalia
g) Other
3) Other
a) Rapid growth or aggressive behavior
b) Tumors in immunosuppressed patients
c) Field fire
d) Other
b. Squamous cell carcinomas (SCC)
1) High risk of local recurrence
a) Ill-defined clinical borders
b) Anatomic sites with high risk of recurrence
(1) Periorbital and canthal
(2) Central third of face
(3) Columella
(4) Preauricular-tragal
(5) Postauricular sulcus
(6) Lower extremities
(7) Genitalia
(8) Temple
(9) Scalp
(10) Lip
(11) Mucosal
(12) Nail bed and matrix
c) History of incomplete removal
d) Some ionizing irradiation-induced lesions
e) Large size
f) Perineural or perivascular tumor
g) Anaplastic histologic differentiation
h) Deep tissue or bone involvement
i) Other
2) Areas of important tissue preservation
a) Nasal tip and alae
b) Lips, cutaneous and vermilion
c) Eyelids
d) Auricular helix and canal
e) Hands and feet
f) Genitalia
g) Nail unit/periungual area
h) Other
3) Tumors associated with high risk of metastasis including those arising
in the following:
a) Bowen’s disease (SCC in situ)
b) Discoid lupus erythematosus
c) Chronic osteomyelitis
d) Lichen sclerosus et atrophicus
e) Thermal or radiation injury
f) Chronic sinuses and ulcers
g) Adenoid type
h) Other
4) Other
a) Rapid growth or aggressive behavior
b) Tumors in immunosuppressed patients
c) Long-standing duration
d) Certain genodermatoses
e) Other
c. Melanoma
Adequate excision is the essential element in the removal of a primary
lesion. Data continue to accumulate supporting the efficacy of narrow
surgical margins in the treatment of melanoma. MMS may prove a useful
technique for certain types and locations of melanoma.
d. Other tumors and lesions
MMS may be of value in the treatment of several less common malignancies
or tumors. These may have ill-defined clinical margins with subclinical
extension that can be identified microscopically. MMS may be used alone or
as an integral part of an overall treatment approach for the following:
1) Verrucous carcinoma
2) Keratoacanthomas (aggressive, recurrent, or mutilating)
3) Dermatofibrosarcoma protuberans
4) Atypical fibroxanthoma
5) Malignant fibrous histiocytoma
(6) Leiomyosarcoma
(7) Adenocystic carcinoma of the skin
(8) Sebaceous carcinoma
(9) Extramammary Paget’s disease
(10) Erythroplasia of Queyrat
(11) Oral and central facial paranasal sinus neoplasms
(12) Microcystic adnexal carcinoma
(13) Apocrine carcinoma of the skin
(14) Certain aggressive locally recurrent benign tumors
(15) Merkel cell carcinoma
(16) Other
e. Miscellaneous
MMS may be of value in certain other special circumstances. This may
include its use alone or in combination with other modalities, such as
radiation therapy or en bloc deep surgery.
B. Diagnostic tests
1. Histology
a. Histologic confirmation is required to establish the diagnosis and may
include the following:
1) Depth of invasion
2) Pathologic pattern
3) Cell morphology
4) Perineural invasion
5) Presence of scar tissue
6) Lymphatic or vascular invasion
7) Other
b. The timing of the initial histologic confirmation may vary. Some cases
may undergo biopsy in advance, whereas others may undergo biopsy at the
time of MMS.
2. Staging
If metastatic disease is suspected, the following may be helpful in defining the extent of local,
regional, or distant metastatic involvement.
Consultation with appropriate specialists may be indicated.
a. Fine needle aspiration or open biopsy of clinically palpable lymph nodes
b. X ray
Routine chest x ray and others as indicated
c. Magnetic resonance imaging
d. Computed tomography
e. Ultrasound
f. TNM classification nomenclature
T = Primary tumor
N = Regional lymph node involvement
M = Distant metastasis
g. Other
C. Inappropriate diagnostic tests
Not applicable
D. Exceptions
Not applicable
E. Evolving diagnostic tests
Monoclonal antibody staining of tissue sections is currently under
investigation.
V. Recommendations
A. Treatment
Skin cancer may be effectively treated by various modalities. Successful treatment of each
individual lesion and patient is dependent on several factors including the clinician’s skill and familiarity
with treatment, availability of treatment modalities, as well as tumor type and patient selection.
1. Nonsurgical
a. Ionizing radiation therapy
1) Superficial (low voltage)
2) Deep (orthovoltage)
3) Interstitial
b. Chemotherapy/immunotherapy
1) Systemic
2) Field
3) Topical
a) 5-Fluorouracil (superficial BCC’s)
b) Other
c. Palliation and/or observation
In some instances the patient’s general health or condition would indicate
palliation and/or observation. The risk/benefit ratio must be considered
individually.
d. Evolving therapy
1) Intralesional
a) Interferon alfa
b) 5-Fluorouracil
c) Other
2) Photodynamic
The patient is given a photoactive compound followed by photoirradiation.
3) Oral and topical retinoids are being evaluated for therapeutic and
chemoprophylaxis management.
4) Other
2. Surgical
a. Shave excision, curettage, and electrosurgery
b. Excision
c. Cryosurgery
d. Laser surgery
e. Mohs micrographic surgery
1) Methods
The fresh tissue technique is synonymous with MMS by today’s criteria and
is the procedure utilized in the vast majority of cases. However, the
original fixed tissue technique may be of value in certain selected cases.
a) Fresh tissue technique
After anesthesia (usually local), all clinically visible tumor is removed.
From the wound thus created, a thin layer of tissue is excised. Care is
taken that this saucer or bowl-shaped layer encompasses the entire wound
surface. The layer is divided into specimens of a size that can be
properly processed in a cryostat. The specimens are mapped on paper, and
the edges of the specimens are painted with dyes to maintain proper
orientation. The specimens are inverted, cut on the cryostat, and stained,
usually with hematoxylin and eosin or toluidine blue. The prepared
specimens are examined by the Mohs surgeon. If residual cancer is seen,
its proper location is noted on the map. Additional surgery is carried out
only at the precise location of residual cancer. All additional tissue
removed is processed and examined exactly as described earlier. The
stepwise procedure is continued until the cancer is removed. In most
instances repair or reconstruction of the wound is required.
b) Fixed tissue technique
The original Mohs chemosurgery technique involved the application of a 40%
zinc chloride fixative followed by excision of the neoplasm and an outer
thin layer of clinically normal-appearing tissue that was processed and
evaluated via the Mohs micrographic technique with successive layered
excisions and accompanying microscopic examinations as required to obtain
a tumor free plane. After a tumor free plane is achieved, the final layer
of fixed tissue is allowed to separate naturally, with healing via
granulation and epithelialization or delayed reconstruction. This method
may be advantageous over the fresh tissue technique in certain instances.
2) Surgical setting
See "Guidelines of Care for Office Surgical Facilities, Parts I and II" (J
AM ACAD DERMATOL 1992;26:676-80 and 1995;33:265-70, respectively).
Additional considerations include the following:
a) Outpatient office surgical settings
(1) Are convenient for patient and physicians
(2) Decrease the risk of nosocomial infection
Are (3) economical
b) Physicians performing MMS should have hospital admitting privileges or
have an arrangement with other physicians for patient management as
necessary.
c) The patient should fully understand the procedure, prognosis, risks,
and alternatives to care.
d) Informed consent should be obtained and documented.
e) Anesthesia
The choice of anesthesia is determined by the surgeon, anesthesiologist,
or anesthetist in conjunction with the patient.
(1) Local (majority of patients)
(2) Regional nerve blocks
(3) Local with sedation (may include oral, sublingual, intramuscular, or
intravenous)
(4) General
(5) Other
3) Mohs micrographic surgical laboratory
a) Adjacent or in close proximity to the operating suite
b) Ability to prepare appropriate frozen section material
c) The Mohs surgeon normally functions as pathologist for slide
interpretation and may be the laboratory director.
d) In certain circumstances permanent tissue sections may be of benefit in
special situations related to tumor characteristics and staining. In these
situations, the permanent sections may be processed at a site other than
the normal Mohs micrographic surgical laboratory. Preprocessing division
of the specimen layer, orientation, and mapping is still performed in the
Mohs micrographic surgical and laboratory setting.
e) In certain difficult-to-interpret tumors or unusual situations, a
second opinion for histopathologic interpretation may be considered.
f) Other
4) Other
a) Reconstruction of surgical defects
Fresh tissue technique usually requires repair/reconstruction that may
(1) Be immediate or delayed
(2) Be coordinated with other surgical specialties (e.g., plastic surgery,
oculoplastics, head and neck surgery, hand surgery)
(3) Be staged reconstruction
(4) Not be required in all cases; wound may heal by second intention.
(5) Require prosthetics in certain cases
(6) Other
c) Postoperative care may include the following:
(1) Appropriate bandages and wound care as indicated
(2) Return visits and follow-up appropriate to the level of service
(3) Prophylactic antibiotics at the surgeon’s discretion
(4) Limitation of activities for a short period as indicated (Most
patients are ambulatory immediately after surgery.)
(5) Nutritional considerations as indicated
(6) Postoperative pain medications as indicated
(7) Other
c) Postoperative findings
(1) Usual and expected postoperative findings may include the following:
(a) Edema
(b) Ecchymosis
(c) Dysesthesia
(d) Discomfort
(e) Scarring
(f) Minor contour imperfections
(g) Asymmetry
(h) Other
(2) Occasional postoperative findings may include the following:
(a) Persistent edema
(b) Persistent dysesthesia
(c) Hyperpigmentation, hypopigmentation
(d) Hematoma, bleeding
(e) Seroma
(f) Drug reaction
(g) Contour imperfections
(h) Pain
(i) Other
(3) Postoperative complications may include the following:
(a) Skin necrosis: may be related to reconstructive procedures or
resulting from infection
(b) Infection - localized or generalized
(c) Large hematoma or seroma
(d) Delayed active bleeding
(e) Nerve damage
(f) Hypertrophic or keloidal scar
(g) Medical complications related to the individual patient’s status
(h) Recurrence of primary tumor: usually rare, may be related to original
lesion or tumor type and other factors
(i) Other
d) Follow-up and patient education
(1) Extended follow-up is essential because of the possibility of
recurrence, metastasis, or the development of other lesions. Frequency and
duration of follow-up is dependent on the individual case.
(2) Prevention and education is an integral part of the care of the
patient. Examples of prevention and education include, but are not limited
to, recommendations about protection from the sun and instruction in
self-examination.
(3) Screening visits for skin cancer are appropriate.
(4) Other
e) Other
VI. Supporting evidence
See Bibliography (Appendix)
VI. Disclaimer
Adherence to these guidelines will not ensure successful treatment in
every situation. Further, these guidelines should not be deemed inclusive
of all proper methods of care or exclusive of other methods of care
reasonably directed to obtaining the same results. The ultimate judgment
regarding the propriety of any specific procedure must be made by the
physician in light of all the circumstances presented by the individual
patient. For the benefit of members of the American Academy of Dermatology
who practice in countries outside the jurisdiction of the United States,
the listed treatments may include agents that are not currently approved
by the U. S. Food and Drug Administration.
Appendix.
Bibliography
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