1. Malignant Melanoma Re-excision Audit
Suzannah Yarwood
Department of Cellular Pathology, Derriford
December 2016

2. Recommendations of RCPATH dataset 2014
Considerable debate about how much to sample and recognise that practice may vary
Sample should be sliced 2-4mm and if macroscopic abnormality these areas must be sampled
Otherwise sample in shortest transverse axis where scar is closest to margin
Approximately 1-4 cassettes

3. If macroscopic abnormality:
Specimens up to 10mm sample entirely
Over 10mm sample pragmatically

4. Other guidelines
Dutch melanoma guidelines advise just taking one central block if primary excision complete
Royal College of Pathologists of Australia recommend if no macroscopic abnormality and previously clear margins sample shortest axis where scar closest to margin (1-4 cassettes)

5. Limited role for examining at all?
One study in the Netherlands showed 0.5% residual melanoma if complete primary excision (De Waal et al 2014) – authors suggest re-excision may be safely omitted in selected cases
However Martin et al (1998) found residual MM in 4 of 167 re-excisions where original margins were clear (2.4%)

6. Methods
Data search for all cutaneous malignant melanoma or lentingo malignana re-excisions between July July 2016
116 identified
Data collected: size of specimen, number of blocks taken, presence of macroscopic abnormality, margin status or original excision

7. Results Range of 1-17 blocks taken per specimen
Average number of blocks/case was 3.5
20% of cases more than 4 blocks taken – however in 25% of those cases macroscopic abnormality was present

8. Residual melanoma or lentigo maligna found in 12 of the re-excisions (10%!!!!)
In addition to this 1 specimen contained atypical melanocytes and 1 containd a severely dysplastic nevus (incompletely excised)
Out of the 12 samples containing residual MM/LM, 5 had previous margins involved, 5 had previously clear margins, (in 2 there was no record of previous margins)
7 had a macroscopic abnormality

9. In 93 of the re-excision specimens there was no macroscopic abnormality and original margins were clear
Of these 4 showed residual/recurrent malignant melanoma or lentigo maligna (4.3%) and a further 1 showed “atypical melanocytes”

10. Discussion Points
Overall we are taking average 3.5 cassettes per specimen – consistent with guidelines
Some outliers (up to 17 cassettes in one case), however guidelines recommend individual discretion
? Would it help to check at cut-up whether previous margins clear – treat with added caution?
4.3% of samples with previously clear margins and no macroscopic abnormality contained melanoma!

11. References
Slater D, Walsh M.“Dataset for Histological Reporting of Primary Cutaneous Melanomas”, Royal College of Pathologists Standards and Datasets for Reporting Cancers. 2014
De Waal A, Vossen R, Aben K, Kiemeny L, Van Rossum M. Limited Role for histopathological examinations of re-excision specimens of completely excised melanomas.Virchows Arch Aug; 45(2):225-31
Martin H, Birkin A, Theaker J. Malignant Melanoma Re-excision specimens – how many blocks? Histopathology 1998: apr; 32(4):362-7