What are the advantages and disadvantages of the different dermatosurgical techniques? Which procedure is suitable for which cases of skin tumors? This review article provides answers.
Deciding which procedure to choose as a physician involved in the treatment of skin tumors should not be done without knowing the strengths and weaknesses of the most commonly used methods. Is micrographic controlled surgery the right choice in every situation? Does it always have to be Mohs? What actually is a Tübingen Torte? Let’s take a brief look at these techniques from a dermatosurgical and dermatopathological perspective.
Bread loaf technique: conventional-histological
The name “bread loaf technique” is used to describe the procedure for processing tissue in pathology. The excidate is cut, like a loaf of bread, and the individual slices are placed in capsules. A section is then taken from each slice on the microtome. This can be used as an example to assess the tumor and its relationship to the incision margins. Special staining is possible and step sections are made if the marginal situation cannot be assessed with certainty. Advantages of this method are the possibility to evaluate excidates independently of their size and to perform special staining, since only a small part of the tissue is “consumed” for diagnostics. The main disadvantage is the incomplete assessment of the incision margin, only a small proportion of which is actually assessed, depending on the size of the excidate and the number of stages made, and the nature of the unassessed margin must be assumed on the basis of tumor entity and growth pattern [1].
Mohs surgery: micrographically controlled
The Mohs technique, named after the surgeon Frederic E. Mohs, is widely considered synonymous with micrographic controlled surgery [3]. By cupping excision of the tumor, compressing the tissue, and freezing it in the cryostat, an assessment of the complete incision margin is performed in a frozen section procedure, which is performed by the surgeon himself, who knows the tumor and the orientation of the excidate best. Necessary re-excision or defect closure follows directly afterwards. The advantage of this – in addition to the possibility of assessing the entire incision margin – is primarily that excision, re-excision and defect coverage can be performed within one day. The limited possibility of making special stains or recuts is seen as a disadvantage. The quality of histologic assessment on frozen sections is considered reduced [2,4,5].
Tübingen cake: 3D histology
This method, developed in the Department of Dermatology at the University of Tübingen, is also a method for recording the entire edge of the incision. On the fresh tissue, the base and outer margins are separated and embedded in such a way that in each case the outer margin (remote from the tumor) can be examined for possible infiltrates. The remaining center of the excidate is slathered as a loaf of bread so that the entity of the tumor and growth pattern can be accurately determined. If necessary, special stains and recuts can be made. If cutting and encapsulation are performed on the fresh excidate by the surgeon himself, the control is also in one hand and by fixation of the already cut tissue the examination results are available on the following day. From this point of view, this third method seems to combine the advantages of the first two. Results are available more quickly than with conventional histology, although not as quickly as with the Mohs procedure [1,2].
Criteria for selection of the method
According to recommendations in the guidelines, incision margin-controlled procedures should be used primarily for excisions in aesthetically challenging regions. Significantly lower recurrence rates compared with conventional histology have been confirmed [2]. The current S2k guidelines recommend excision with complete incision margin control for both basal cell carcinoma [4] and squamous cell carcinoma of the skin [5]. Conventional histological processing (bread loaf) should only be performed with appropriately larger, tumor-adapted safety margins, which would lead to unnecessarily large defects and more complex defect coverage with regard to the alternative techniques mentioned. Clearly, a kerosene section process is also described here as superior to the cryostat process. An expansion of the indications for melanoma in situ, melanomas of the face and the acras are under discussion [6,7].
In clinical practice, 3D histology has been established and proven as a procedure with complete incision margin control. If not already done prior to referral, a diagnosis is made by small biopsies (punch, shave) in cases not clearly clinically attributable to a non-melanocytic entity. If localization and tumor size suggest primary closure after excision, a one-stage procedure is planned, otherwise a two-stage procedure with excision in the first step and post-excision or defect coverage in the second step after 48-72 hours. Safety distances for macroscopically clearly delineated tumors are chosen between 2-3 mm, and between 3-4 mm for blurred boundaries. Temporary wound coverage in two-stage procedures is achieved, for example, with a silver-coated foam dressing sewn into the defect. The first procedure is usually performed on an outpatient basis under local anesthesia, and the modalities of the subsequent procedure(s) depend on localization, tumor size, type of defect coverage, and patient-related factors.
Excidates are cut and marked by the surgeon while still in the operating room. Appropriate guidelines were developed in close cooperation with the pathologists who made the findings.
In summary, this method for the surgical treatment of non-melanocytic skin tumors is considered a feasible and patient-friendly procedure. Intraoperative cutting can usually be performed in parallel with hemostasis and (temporary) defect closure and does not require additional time as surgeons gain experience. With the dressing technique described, there is hardly any pain, secondary bleeding is rare, and no wound infections have occurred to date.
Prior to defect closure, which is usually performed by means of local flap plasty, the wound bed and edges are freshened with a sharp spoon; excision of the edges and thus enlargement of the defect size is not necessary. The method is used for all types of basal cell carcinoma and squamous cell carcinoma of the skin. For other non-melanocytic tumor entities, decisions are made on a case-by-case basis and according to the literature.
Patients accept the waiting interval between operations well. It should be noted that even with frozen section examination, the excidates are often not processed at the same institution as originally described in the Mohs technique, but are transported to an external laboratory and examined there, which also results in longer waiting times between excision and post-excision or defect coverage.
Literature:
- Glatz K: Quality guidelines SGPath. Pathology, University Hospital Basel, in collaboration with the Dermatohistopathology Working Group of SGPath and SGDV January 2019. Status 1/2019; 1-17. www.sgpath.ch/docs/QRL/QRL_SGPath_Haut_2019.pdf
- Boehringer A, et al: Analysis of incomplete excisions of basal-cell carcinomas after breadloaf microscopy compared with 3D-microscopy: a prospective randomized and blinded study. J Cutan Pathol 2015: 42: 542-553.
- Ladda MA, Lynde CW: Mohs Micrographic Surgery: Development of the technique. J Cutan Med Surg 2019; 23(2): 236.
- Lang BM, et al: S2k guidelines “Basal cell carcinoma of the skin” (update 2017/2018). AWMF, www.awmf.org/uploads/tx_szleitlinien/032-021l_S2k_Basalzellkarzinom-der-Haut_2018-09_01.pdf
- Breuninger H, et al: S2k guidelines – squamous cell carcinoma of the skin. JDDG 2013. First published: May 8, 2013. https://doi.org/10.1111/j.1610-0379.2012.8018_7.x
- Elias ML, Lambert WC: Surgical Management of Localized Melanoma: A National Cancer Database Retrospective Review. Br J Dermatol 2019 Mar 25. doi: 10.1111/bjd.17901. [Epub ahead of print]
- Guidelines Program Oncology (German Cancer Society, German Cancer Aid, AWMF): Diagnostics, Therapy and Follow-up of Melanoma, Consultation Version Long Version 2.0, 2016, AWMF Registry Number: 032/0240L, Status: April 2016. http://leitlinienprogramm-onkologie.de/Melanom.65.0.html.
DERMATOLOGIE PRAXIS 2019; 29(2): 42-43
