Indications to Mohs Micrographic Surgery (MMS)

June 10, 2020 10:00 am Published by

Mohs Micrographic Surgery is a Gold standard treatment of cutaneous malignancies because it optimizes all 3 standard principles that direct the management of all malignancies:

  1. Oncologic Cure
  2. Preservation of function
  3. Restoration of cosmetic

Mohs Micrographic Surgery has achieved the highest cure rates for both the residual and recurrent malignancies. Following are the indications to Mohs Micrographic Surgery:

Size of Tumor:

An increase in tumor size is directly correlated with an increased risk of metastasis and recurrence. When the size of the tumor increases, it increases the subclinical spread and hence causes greater tissue destruction and deep invasions. Metastasis in Squamous cell carcinoma <2 cm is 9.1%, and Metastasis in Squamous cell carcinoma >2 cm is 30.3%. The definitive cure for larger tumors is very difficult with conventional surgeries alone. Therefore, Mohs Micrographic Surgery must be considered for Squamous cell carcinoma and Basal cell carcinoma of 2 cm (or >2 cm).

Patient Features:

Patients that are on high-risk require Mohs Micrographic Surgery have common features:

  1. Multiple malignancies: Patients with multiple malignancies are at higher risk and are indicated to MMS.
  2. Continuously developing tumors: They continue developing tumors on a long term basis and MMS is highly recommended.
  3. Aggressive tumors: Aggressive tumors cause greater tissue destruction, recurrence, and metastasis. Therefore, patients are at higher risk.
  4. Immunosuppressed patients: Immunosuppressed patients are definitely at higher risk. The incidence of Squamous cell carcinoma is 5–10 times that of the normal population.
  5. Actinically damaged skin: Nonimmunosuppressed but severely clinically damaged patients are also at high risk for multiple malignancies.
  6. Young patients: Morpheaform Basal cell carcinoma is 4.25 times more common in young adults than in the general population. MMS is highly recommended for these patients.

Histologic Features:

Management in oncology is strongly influenced by histologic features. For Basal cell carcinoma and Squamous cell carcinoma, specific histological types are associated with higher rates of tissue destruction, recurrence, and metastasis. Mohs Micrographic Surgery is indicated and has been proven effective for these more aggressive malignancies

Basal cell carcinoma (BCC):

Numerous histological variants of basal cell carcinoma exist. Although several subtypes may exist within the same tumor. Clinically relevant aggressive subtypes include:1. Morpheaform BCC: It is a prototype of aggressive tumors. Morpheaform Basal Cell Carcinomas have poorly defined borders, and are typically present in younger patients.2. Infiltrative BCC: It is also a prototype of aggressive tumors. Compared to other BCCs, Infiltrative BCCs are mostly associated with incomplete excisions and a tendency to recur.3. Micronodular BCC: Micronodular BCC also extends widely. The mean margin for clearing all subclinical extensions of micro nodular BCC was 5.4 ± 2.77 mm, versus 3 ±1.6 MMM for nodular BCC.4. Basosquamous BCC: Basosquamous (met atypical) BCC is rare. It has features of both BCC and SCC and behaves more aggressively than the SCC component. The met atypical subtype is common histology among BCCs that have metastasized. For these tumors, Mohs Micrographic Surgery is strongly considered irrespective of other risk factors.

Squamous cell carcinoma:

SCC is inherently (malignant) than BCC. Both SCC and its variant features (Bowen’s disease, verrucas carcinoma, erythroplasia of Queyrat) may be effectively treated with Mohs Micrographic Surgery. Histological features of poor prognosis for all SCC poor differentiation, infiltrate and neoplastic patterns, deep invasion (>4 mm Clark level 4 or greater), and perineural disease. For poorly differentiated SCC, the recurrence rate is doubled and metastasis is tripled. The recurrence rate for poorly differentiated SCC is 32.6% for Mohs Micrographic surgery and 53.6% for Non-Mohs modalities. The overall cure rate for SCC with MMS is 97% with complete margin control. Hence, Mohs Micrographic Surgery is highly recommended.

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This post was written by Michael Porter

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