๐ ็ธฝ็ฎ้ ๏ฝ ๐ ่ฑๆๅๆ๏ผๆฌ็ฏ๏ผ ๏ฝ ๐ ๅฎๆด็ฟป่ญฏ ๏ฝ โญ ็ฒพ่ฏ็ญ่จ
Introduction
CHAPTER 30 Advanced Techniques
and Special Stains in Mohs Micrographic Surgery
Jessica M. Donigan Benjamin Jones Alice Frigerio Keith L. Duffy
SUMMARY
Micrographic surgeons must have a working knowledge of pathology techniques
including immunohistochemical stains and newly developed and developing molecular diagnostics.
From a practical standpoint, with the exception of lentigo maligna (and
potentially superficially invasive melanomas), there are few tumors that benefit from the addition of frozen section immunohistochemistry at the time of micrographic surgery.
Beginner Tips
Maintain regular contact with colleagues in dermatopathology. The perspective of the
pathologist and surgeon must be mutually understood.
Personal visits are better than phone calls which are better than e-mails which are
better than text messages.
Expert Tips
Poorly differentiated tumor cells, dense inflammation, perineural invasion, and
fibrosis are all situations in which immunohistochemical stains may be useful. The most widely used is AE1/AE3, a pan-keratin marker, which will label most carcinomas.
If there is specific concern for BCC, a Ber-EP4 stain can be performed.
CK7 for EMPD may be helpful in Mohs frozen sections. The main caveat to using this
stain is the usually large sizes of the pieces of tissue to be examined in EMPD.
Donโt Forget!
New terms are introduced into the literature by both clinicians and pathologists in an
attempt to better define pathological entities and stratify risk. In recent years, the terms atypical intradermal smooth muscle neoplasm (instead of cutaneous leiomyosarcoma) and pleomorphic dermal sarcoma/undifferentiated pleomorphic sarcoma have been introduced. Pleomorphic dermal sarcoma/undifferentiated pleomorphic sarcoma is a distinct entity from AFX and has a worse prognosis.
Pitfalls and Cautions
CD34 as a frozen section immunohistochemical stain for DFSP treated by MMS is
discouraged. The nonspecific background staining, as well as the labeling of endothelial cells, makes this extremely difficult to interpret on frozen section pathology.
Some tumors may also benefit from adjuvant therapy, such as postoperative radiation.
Patient Education Points
Patients should be explained that many rarer or more aggressive tumors have a high
defect to lesion ratio, so an ostensibly small tumor may end up leading to a very large defect.
The high cure rates cited for Mohs surgery are generally applicable to primary low-
risk tumors; tumors with negative prognostic factors (infiltrative or perineural
patterns) or unusual tumor types (Merkel cell carcinoma, DFSP) may be associated with significantly higher recurrence rates.
Billing Pearls
Billing for immunohistochemical stains is in addition to standard Mohs layer billing,
and is generally billed on a per-specimen basis with code 88342 for the first antibody followed by 88341 for each additional antibody. If multiple separately identifiable antibodies are applied to the slide, use one unit of 88344.
CHAPTER 30 Advanced Techniques
and Special Stains in Mohs Micrographic Surgery
INTRODUCTION
Even in the busiest Mohs micrographic surgery (MMS) practice or at a tertiary/quaternary referral center, special stains are not used on a frequent basis. Treating these cases not only requires a technically proficient micrographic surgeon and laboratory, but also the knowledge of the latest pathology techniques and available immunohistochemistry stains for both permanent and frozen section pathology. While the ability to see 100% of the surgical margin using the MMS technique is certainly an advantage, there are limitations to both this technique and the use of frozen section pathology in certain circumstances. For the specialized tumors discussed in this chapter, both good judgment and an excellent working relationship with a colleague in dermatopathology are a necessity.