Subtipo de CBC y numero de estadios en Mohs.

 Published in Dermatology

Journal Scan / Research · March 16, 2022

Correlation of Basal Cell Carcinoma Subtype With Subclinical Extension During Mohs Micrographic Surgery

Journal of the American Academy of Dermatology

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• In this multicenter prospective study involving 17 Mohs surgeons, 1686 cases of basal cell carcinoma (BCC) undergoing Mohs micrographic surgery (MMS) were analyzed. The objective was to correlate the histological subtype of BCC with the likelihood of subclinical extension as defined as the number of MMS stages required to clear the tumor. Morpheaform, infiltrative, metatypical, mixed, and superficial BCCs had a high risk of subclinical extension, with an average number of MMS stages of 1.8 or higher. Basosquamous, micronodular, nodular, and unspecified subtypes had an average number of MMS stages of 1.6 or lower. A change between BCC subtype at the index biopsy and the BCC subtype at the final MMS stage was most likely to occur with superficial BCC.

• While superficial BCC is not deemed "appropriate" for MMS, it was as likely to exhibit subclinical extension as the "aggressive" subtypes of BCC.

–  Katherine M. Stiff, MD

Written by Glenn D. Goldman MD

Multiple options exist for the treatment of basal cell carcinoma. Mohs surgery is the most exacting method of tumor removal. Mohs surgery is particularly useful in the removal of lesions which may have subclinical extension (SCE).   

This study was a detailed, prospective, multicenter investigation of lesions treated by Mohs surgery. The primary endpoint was to determine the types of basal cell carcinoma that were likely to exhibit SCE. The authors demonstrated that morpheaform, infiltrative, metatypical, mixed, and superficial BCC required a higher mean number of stages for complete tumor removal. Keratotic, micronodular, nodular, and unspecified lesions were less likely to have SCE. The authors note that superficial BCC may have SCE and that Mohs micrographic surgery should be considered.

The difference in stages between high-degree SCE and low-degree SCC was highly statistically significant, but the absolute difference (1.9 per case vs 1.6) was small. In this study, the authors did not distinguish SCE between a deep positive margin and a superficial epidermal margin. It is not clear that epidermal SCE for a superficial BCC on area L has the same implication as deep muscle SCE for an infiltrative BCC on the nose.      

The Mohs AUC have functioned very well to define BCCs that are appropriate for Mohs surgery. The majority of BCCs, including superficial BCC, are appropriate in areas H and M. It remains unclear that Mohs micrographic surgery is appropriate for lesions of superficial BCC in area L, as many appropriate treatments are available. A few buds of BCC on a peripheral margin on the back are not prognostically equivalent to single-cell invasion of muscle or fascia, and they need not be treated equivalently.

Abstract

BACKGROUND

Traditionally "aggressive" histologic subtypes of basal cell carcinoma (BCC) are more likely to quantitatively exhibit subclinical extension (SCE), requiring more stages during Mohs micrographic surgery and therefore larger margins upon excision. However, the tendency for SCE has never been compared between histologic subtypes of BCC in a prospective manner.

OBJECTIVE

To prospectively correlate the histologic subtype of BCC with the likelihood of subclinical extension as defined by the number of MMS stages required to clear tumor.

METHODS

In a prospective, multi-center study involving 17 Mohs surgeons in 16 different practices across the United States, 1,686 cases of BCC undergoing MMS were collected. Patient demographics, tumor characteristics, number of MMS stages required for tumor clearance, and specific BCC subtypes noted on both index biopsy and final MMS stage were recorded.

RESULTS

Analysis of the average number of MMS stages for each histologic subtype required to clear tumor revealed two distinct degrees of SCE (P < 0.0001): high (higher than average) risk of SCE (1.9 stages, 1.0 SD), and low (lower than average) risk of SCE (1.6 stages, 0.9 SD). Subtypes of BCC within the high category were morpheaform (2.1), infiltrative (1.9), metatypical (1.9), mixed (1.8), and superficial (1.8). The low category included BCC subtypes of basosquamous (1.6), micronodular (1.6), nodular (1.6), and unspecified (1.5). Three hundred twenty-four cases (22.0%) manifested histologic subtype (HS) drift, or a change in subtype from index biopsy to final MMS stage. Superficial BCC was the only subtype that showed an increase in prevalence from index biopsy to final MMS stage (16.0% to 25.8%, P < 0.0002).

LIMITATIONS

Histologic subtypes from index biopsy may not be representative of all histologic subtypes present, resulting in sampling bias.

CONCLUSION

Subclinical extension of superficial BCC was as likely as SCE of BCC subtypes which are considered "aggressive" and are deemed "appropriate" for MMS by the AUC. Our study also found that when HS drift occurs, the most likely subtype to extend subclinically is superficial BCC.

Journal of the American Academy of Dermatology

Correlation of Basal Cell Carcinoma Subtype with Histologically Confirmed Subclinical Extension During Mohs Micrographic Surgery: A Prospective Multi-Center Study

J Am Acad Dermatol 2022 Feb 26;[EPub Ahead of Print], GFS Lim, OA Perez, JA Zitelli, DG Brodland