Flashcards in Mohs Micrographic Surgery and Cutaneous Oncology Deck (57):
Mohs provides the highest cure rate for tumours that spread by direct extension.
MOHs has clearance approx 80% for recurrence rate
Critical in the process is that the skin edge and deep surface are visualized in one plane on the glass slide, and thus the entire margin can be analysed
Mohs surgery originally involved the use of zinc chloride (as a fixative), combined with stibnite (as permeant) and bloodroot powder (Sanguinaria Canadensis) (as agglutinant).
T This is the same as black salve!
Conventional breadloaf sectioning of tumours allows for examination of 10% of the tumour’s margin.
Indications for MOHs micrographic surgery includes tumour larger than 2cm in diameter
Tumours of the skin of the upper lips are usually SCC, while those of the cutaneous lower lip are most commonly BCC.
F Other way round.
Most Mohs laboratories use routine hematoxylin and eosin staining for all specimens.
Technical errors are the most common cause of local recurrences after Mohs surgery.
Large or thick tumours may be debulked using a curette as this may further delineate margins and reduce the number of layers necessary to obtain clear margins
A saucer-shaped specimen with 45degree bevelled edges is ideal so that the specimen may be flattened
F 30 degrees. Flattening means that the bottom and margins can be sectioned by the Mohs technician in the same plane
The specimen has its non-epidermal edges stained to allow proper orientation. At least four colours are used for each specimen to allow for adequate orientation
F Two to three colours
In the laboratory, vertical sections are taken
F Specimen is placed bottom side up toward the microtome stage to allow horizontal sections
The tissue may be immediately frozen with tetrafluoroethylchloride or liquid nitrogen and then transferred to the cryostat for thorough freezing
Toluidine blue can be used for BCCs but has poor optical clarity
F Favoured by some for its optical clarity, but the process of immunostatins is impractical for routine use
Infiltrative BCC is not distinctive clinically, but histologically contains islands of tumour cells with a spiked appearance in narrow cords within a hyalinised stroma
BCCs with aggressive histology (ie. ulcerative, metatypical, morpheaform, infiltrative forms) require more Mohs layers to achieve tumour-free margins.
BCC tumour size does not affect the extent of subclinical spread.
Recurrent BCCs after radiotherapy often have morphoeaform or metatypical patterns.
Metastatic BCC occurs in less than 0.5% of cases.
Risk factors for metastatic BCC include tumour invasion into cartilage, bone, skeletal muscle or parotid gland, previous XRT and previous treatment with any modality.
The nose is the most common site from which metastatic spread of BCC occurs.
F The ear.
BCC metastasis occurs haematogenously only to lungs, bone&skin.
F Also through lymphatics.
Biologically aggressive subtypes of SCC include cystic SCC, adenoid SCC, clear cell carcinoma and spindle cell carcinoma.
SCCs arising in immunocompromised pts tend to be more aggressive and have higher metastatic rates.
SCCs that are more likely to recur or metastasize should not be considered for Mohs.
There is an increased risk for metastatic spread for SCCs that are histologically moderately to poorly differentiated, and for facial lesions, particularly temple, nose, lip, periocular, or periauricular.
SCCs with perineural invasion do not have an increased risk of recurrence.
Mohs for recurrent SCC can provide local cure rates of 94% or greater.
For SCC the combination of chemotherapy agents cisplatin, 5-FU and bleomycin had an overall response rate of 79%
For advanced head and neck SCC cetuximab, a monoclonal antibody inhibitor of epidermal growth factor receptor, has been shown to have effect
Induction chemotherapy with docetaxel, cisplatin and flurorouracil offers increased median time survival for locally advanced SCC of head and neck when used alone
F When used with concurrent chemoradiotherapy
Incidence of nodal mets greatly increases with Breslow depth
T Used for invasive melanomas intermediate in depth between 1 and 4mm
Radiotherapy is the treatment of choice for verrucous carcinoma.
F Becomes more aggressive after XRT.
Mohs micrographic surgery has been successfully used to treat Merkel cell carcinoma, a neuroendocrine tumour of the skin
The pathogenesis of Merkel cell carcinoma is linked to a virus in some cases
T Merkel cell polymavirus
Merkel cell carcinoma has local recurrence rates of 30%, regional node involvement rates of up to 50%, and metastatic rates of 40%.
Survival rates for Merkel cell carcinoma statistically correlate with nodal status.
A 2cm margin is recommended for primary excision of Merkel cell carcinoma.
Although the optimal treatment of Merkel cell carcinoma is unknown, radiation therapy is a commonly used adjunct to surgery to improve local control
Adjunctive chemo for Merkel cell has been proven to improve survival
F No chemotherapy protocol has been shown to improve survival
Adjuvant XRT is recommended for large, recurrent or incompletely excised Merkel cell carcinomas.
Dermatofibrosarcoma protuberans is characteristically a rapid growing, locally aggressive malignant tumour of the skin
F A slow growing tumour
Dermatofibrosarcoma protuberans is most common on the distal extremity.
F Trunk, upper thighs, groin.
Recurrence rates after wide excision of DFSP can be as high as 60%.
DFSP rarely metastasize.
DFSP tumours over 2cm in dimaeter need a margin of 1.5cm
1.5cm margin for DFSP less than 2cm diameter
Larger tumours – 2.5cm margin
DFSP stains positively with CD34
Atypical fibroxanthoma (AFX) usually presents as an ulcerated, erythematous nodule or plaque on heavily actinically damaged skin of the head and neck in older men
Malignant fibrous histiocytoma has a worse prognosis than atypical fibroxanthoma.
Malignant fibrous histiocytoma is a soft tissue sarcoma with a better prognosis with than AFX
F Less favourable
In malignant fibrous histiocytoma special stains may be of value with CD74 positive in 90% of patients
Microcystic adnexal carcinoma (MAC) occurs most commonly on the periorbital region of elderly men.
F Upper lip in middle-aged women.
MAC frequently invade into skeletal muscle, and perineural invasion is often seen.
Local recurrence rate for MAC excised with standard excision is 10%.
F Almost 50%. Mohs is 10%.
Primary eccrine adenocarcinoma (eccrine porocarcinoma) is radioresistant.