Recurrence rates of cutaneous squamous cell carcinoma of the head and neck after Mohs micrographic surgery vs. standard excision: a retrospective cohort study.

BACKGROUND: Recurrent cutaneous squamous cell carcinoma (cSCC) has been associated with an increased risk of local functional and aesthetic comorbidity, metastasis and mortality. OBJECTIVES: To compare the risk of recurrence between Mohs micrographic surgery (MMS) and standard excision for cSCC of the head and neck. METHODS: This was a retrospective cohort study of all patients with a cSCC treated with MMS or standard excision at the departments of dermatology of a secondary or tertiary care hospital in the Netherlands between 2003 and 2012. To detect all recurrences, patients were linked to the Dutch pathology registry. To compare the risk of recurrence between MMS and standard excision, hazard ratios (HRs) were used adjusted for clinical tumour size > 2 cm and deep tumour invasion. RESULTS: A total of 579 patients with 672 cSCCs were included: 380 cSCCs were treated with MMS and 292 with standard excision. The risk of recurrence was 8% (22 of 292) after standard excision during a median follow-up of 5·7 years [interquartile range (IQR) 3·5-7·8], which was higher than the 3% (12 of 380) after MMS during a median follow-up of 4·9 years (IQR 2·3-6·0). The cumulative incidence of recurrence was higher for standard excision than for MMS during the entire follow-up period of 8·6 years. Carcinomas treated with MMS were at a three times lower risk of recurrence than those treated with standard excision when adjusted for tumour size and deep tumour invasion (adjusted HR 0·31, 95% confidence interval 0·12-0·66). CONCLUSIONS: MMS might be superior to standard excision for cSCCs of the head and neck because of a lower rate of recurrence.

Mohs micrographic surgery of rare cutaneous tumours.

BACKGROUND: Recurrence rates after Mohs micrographic surgery (MMS) for rare cutaneous tumours are poorly defined. OBJECTIVE: To investigate the recurrence rate after MMS for rare cutaneous tumours at a university centre. METHODS & MATERIALS: Retrospective review of all rare cutaneous tumours treated with MMS at a large university centre between January 2008 and December 2012. To detect all recurrences, patients were linked to The Nationwide Network and registry of histo- and cytopathology (PALGA). RESULTS: In total, 80 patients with 80 tumours were included. Tumour types included dermatofibrosarcoma protuberans (27), atypical fibroxanthoma (22), Merkel cell carcinoma (8), microcystic adnexal carcinoma (9), sebaceous carcinoma (6), extramammary Paget's disease (2) and other (6). Mean follow-up time was 3.7 years (standard deviation 1.4) during which two atypical fibroxanthomas recurred (2.5%). CONCLUSION: This large case series shows that MMS is an appropriate treatment for rare cutaneous tumours with a recurrence rate less than 3%. Preferably, MMS for rare cutaneous tumours is performed in experienced multidisciplinary centres to further improve the quality of treatment.

Reliability of diagnosis from Mohs slides: interpersonal and intrapersonal agreement on basal cell carcinoma presence and histological subtype.

BACKGROUND: The success of Mohs micrographic surgery (MMS) depends partly on the correct diagnosis of slides. OBJECTIVES: To determine reliability of diagnosis from Mohs slides. METHODS: This was a prospective study evaluating the reliability of diagnosis from Mohs slides of basal cell carcinoma (BCC) presence, BCC location on the slide and BCC subtype among six raters who independently assessed 50 Mohs slides twice with a 2-month interval. Slides were randomly selected whereby difficult-to-diagnose slides were oversampled. For each slide, a reference diagnosis was established by an expert panel. Cohen's kappa (κ) was calculated to determine levels of agreement interpersonally (rater vs. reference diagnosis) and intrapersonally (rater at T1 vs. T2). Multivariable logistic regression was used to determine independent risk factors for slides with interpersonal discordant diagnosis. The variables studied were BCC presence, whether a slide was scored as easy or difficult to diagnose, review duration of the 50 slides, profession and years of experience in diagnosis from Mohs slides. RESULTS: Interpersonal and intrapersonal agreement were substantial on BCC presence (κ = 0·66 and 0·68) and moderate on BCC subtype (κ = 0·45 and 0·55). Slides that were scored as difficult to diagnose were an independent risk factor for interpersonal discordant diagnosis on BCC presence (odds ratio 3·54, 95% confidence interval 1·81-6·84). CONCLUSIONS: Reliability of diagnosis from Mohs slides was substantial on BCC presence and moderate on BCC subtype. For slides that are scored difficult to diagnose, a second opinion is recommended to prevent misinterpretation and thereby recurrence of skin cancer.

Additional review of Mohs slides to optimize Mohs micrographic surgery.

BACKGROUND: One significant risk factor for recurrence after Mohs surgery is misinterpretation of slides. OBJECTIVES: To determine how often pathologists detected incompletely excised basal cell carcinoma (BCC) on Mohs slides and to determine risk factors for incompletely excised BCCs. METHODS: This retrospective study included 1653 BCCs treated with Mohs surgery in a university hospital between 2007 and 2011. For routine quality assurance, all slides were additionally reviewed by a pathologist within 1 week of the procedure. For this study, all cases that had divergent interpretations were re-evaluated by a Mohs surgeon and a pathologist. Mixed-effects logistic regression models with Mohs surgeon effects as random effects were used to determine risk factors for incompletely excised BCC. RESULTS: Incompletely excised BCCs were detected in 31 cases (2%), in which defects > 20 mm in diameter were an independent risk factor (odds ratio 3.58, 95% confidence interval 1.55-8.28). Other studied variables (i.e. aggressive subtype, previously treated BCC, location on nose and > 2 Mohs stages) did not affect the risk of incompletely excised BCCs. CONCLUSIONS: The additional review of Mohs slides might increase accurate interpretation, especially in large BCCs.