and those located on high-risk anatomic sites, intraoperative frozen section evaluation is the treatment of choice. This evaluation is especially necessary before extensive reconstructive surgery is planned. It is frequently performed in many institutions where it is difficult to perform a complete Mohs micrographic surgery (MMS) procedure due to health insurance limitations and other reasons. In addition, it is especially commonly performed for surgeries under general anesthesia in which resection and reconstruction are completed simultaneously. However, in the conventional histological method of examining tumor margins, only certain slices perpendicular to the tumor are examined; therefore, an extension between the slices can be missed.

42.2.2 Present State of MMS in East Asia

Previous reports or studies of MMS from East Asia are very limited. Those that have been completed focused on extramammary Paget’s disease (EMPD) [8], dermatofibrosarcoma protuberans (DFSP) [9], SCC of the lower lip [10], and some adnexal tumors [11, 12] reported by particular institutions in Korea and Taiwan.

Lee et al. [8] reported successful results of EMPD treatment. The local recurrence rate was 10% for MMS compared with 30% for wide excision. They concluded that MMS is superior to conventional wide excision for EMPD in Asians.

From the same institution, it was also reported that treatment of DFSP by MMS resulted in a low recurrence rate with possible benefits of smaller defects, as compared to wide local excision [9]. Additionally, MMS has been reported to be a successful treatment modality for rare types of skin tumors in East Asia, including squamoid eccrine ductal carcinoma [12] and syringo-cystadenocarci- noma papilliferum [11].

However, this technique is relatively specialized and is not routinely available in most dermatologic units because it is time-consuming, expensive, and requires the expertise of specially trained Mohs surgeons and technicians. In institutions in which MMS is unavailable, conventional excision with postoperative histological margin assessment

remains the main form of surgical treatment. Therefore, in East Asia, where skin cancers are not as prevalent and where resources are limited, the feasibility and cost-effectiveness of setting up a Mohs unit are debatable. To save time and increase the accuracy of histological analysis of surgical margins, it is easier and more convenient to add a modified MMS technique to conventional intraoperative histological evaluation than to introduce a completely new MMS system. We recently reported a modified method of MMS for nonmelanoma skin cancers in Japan [13] (Fig. 42.1).

42.2.3 Modified MMS in Japan

Intraoperative histological evaluation by frozen section analysis is usually limited to suspicious areas. Therefore, the accuracy of such analysis of surgical margins of skin cancer is highly dependent on the methods used to obtain and analyze the margins. For institutions at which it is difficult to perform MMS, we introduced the double-bladed scalpel (DBS) as a novel, simple method for complete histological margin control [13]. A basic element of our procedure is resection of the whole tumor followed by excision of an additional outer layer for complete histological evaluation of the excision margins in three dimensions (Fig. 42.2a–f). This element involves performing the first two steps of MMS together by using permanent sections for histological evaluation of the tumor and using the frozen section only in re-excision of an additional outer layer from the tumor defect. This improves the pathodiagnostic reliability of conventional intraoperative histological evaluation.

Summary: Conclusion

•Complete histological margin control using a double-bladed scalpel may be easily applied to standard intraoperative frozen section evaluation in many institutions in East Asian countries where Mohs micrographic surgery is difficult to perform.

Fig. 42.1 Using the “double-blade method,” parallel excisions are made and the gross tumor is excised in a bowl shape. An additional layer of tissue, along with 2-mm strips of the outer skin, is subsectioned into two to four regions and excised in a uniform width by scissors as in MMS. The excised tumor is then sent to the pathology lab and examined by breadloaf sectioning.

Additional resected tissue is flattened and examined by en face frozen sectioning. If a tumor-positive margin in a re-excision specimen is obtained, additional layers of tissue are excised from the tumor-positive area. This procedure is repeated until negative margins are confirmed

Fig. 42.2 Poorly defined nodule with a small amount of pigmentation on the left ala. (a) Initial surgical margin is 2 mm (solid line) from the clinical border (dotted line). (b) Using a DBS, parallel excisions are made around the tumor. (c) Gross tumor with initial surgical margins is excised in a bowl shape along the DBS inner excision. (d) Lateral margin specimen with

2-mm strips of outer skin is excised in a uniform width by scissors, taking great care to avoid tearing tissue. (e) Specimens from an additional layer are flattened, and sectioning is started from the true margin side. (f) Final defect after complete excision of tissue under histological evaluation by en face frozen section is reconstructed using a combined flap from the left cheek

42.3Conclusion

Due to differences among countries in insurance systems and surgical approaches, MMS is still uncommon in most Asian countries. Surgical excision with wide margins is the standard treatment for low-risk nonmelanoma skin cancer. For high-risk skin cancer, intraoperative histological evaluation to control the surgical margins is widely used instead of MMS. Complete histological margin control using a DBS may be easily applied to standard intraoperative frozen section evaluation in many institutions where MMS is difficult to perform. It is far less time-consuming and can be easily used by surgeons with existing systems, even in East Asian countries.

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