Background
Incomplete excision rates of melanoma in situ (MIS) up to 50% have been reported in literature (1). There is no standardised histological processing of MIS specimens in accredited laboratories internationally that we are aware of. We would like to investigate our rates of complete histological clearance of MIS with >3mm margins based on our local histological processing protocols (2).
Methods
Retrospective review of 237 cases of head and neck MIS treated in a single Plastic Surgery department by surgical excision over a 5 year period. Clinicopathologic records reviewed for patient, lesion, excision and histological details to calculate the clinical margins taken and correlate with histological margins achieved.
Results
All specimens underwent 2mm micro-sectioning histological analysis. Of the 207 cases that received histological clearance of >3mm, 81.2% were cleared by taking 7mm macroscopic margins whereas 12mm macroscopic margins achieved clearance in 97.6%. This corresponds with clearance rates of 86.5% after 1 wide local excision (WLE) and 98.1% after 2 WLE.
Discussion
Our findings suggest a good level of histological clearance achieved in the majority of cases diagnosed with MIS from first biopsy analysis. This may not translate clinically into rates of observed clinical recurrence in our treated cohort as long term follow up data will be required to evaluate this. Our mean follow up is 8.8 months (SD 11.9) and 3 out of 207 cases had clinical recurrence in this follow up period.
Conclusion
Our unit in Waikato managed to achieve >3mm clearance in 97.6% of cases being managed over a 5 year period. Long term follow up is required to correlate clinical recurrence with histological clearance.