FISHing for
tricky naevi
Dr Hardeep Singh Manchester BAOP 2011
Over diagnosis of MM
• Inappropriate therapy • Psychological burdens• Life assurance issues
Under-diagnosis of MM
• Inadequate treatment of a deadly cancer
FISH for skin melanocytic lesions
• Now a well established tool in the analysis of challenging, controversial, or ambiguous melanocytic lesions
• Fluorescence in situ hybridization (FISH) as an ancillary diagnostic tool in the diagnosis of melanoma. Gerami P, et al Am J Surg Pathol. 2009 Aug;33(8):1146-56.
Approach
• Utilizing commercially available probes (Vysis) that assess copy numbers of:
– RREB1 (6p25)– MYB (6q23)– CCND1 (11q13)– In relation to a centromeric reference
point Cep6.
Methodology
• Assessment of 3 areas of 10 adjacent cells each….30 cells in total.
• A positive FISH result is if any of the following criteria are met:
• Gain in RREB1 relative to CEP6 >55%• Gain in RREB1>29%• Loss of MYB relative to CEP6 >40%• Gain in CCND1 >38%
‘…….. 86.7% sensitivity and 95.4% specificity in the validation cohort. The test also correctly identified as melanoma all 6 of 6 cases with ambiguous pathology that later metastasized. ……………………………………. this assay can have significant clinical impact and improve classification of melanocytic neoplasms with conflicting morphologic criteria’.
• When does junctional activity burn out…??
• What is significance of junctional activity over banal, maturing stromal component?
Conjunctival naevi
Service evaluation validation of FISH in conjunctiva
• 5 naevi
• 5 melanosis without ‘atypia’
• 10 cases of atypical melanosis / C-MIN / in-situ MM with invasive MM in same eye
Outcome• 5 Naevi….FISH negative• 5 melanosis without ‘atypia’..FISH negative• 10 cases of atypical melanosis /C-MIN/In-situMM
and invasive MM….all FISH positive.
• Correlated with results of a previous paper: Distinction of conjunctival melanocytic nevi from melanomas by FISH Busam et al. J. Cut. Pathol. 2010. Only looked at 2 ‘equivocal cases’…1 case was clearly in-situ on morphology…other was clearly invasive….fragmentation and tangential cutting were the inclusion criteria for ‘equivocal classification’.
• Technique works in our hands
Study of tricky naevi
7 patients4 male ; 3 females.
Males: 23, 31, 33, 46, Females: 46, 59, 70
All with naevus-like lesions clinically.Some change in colour / size noted.
Excised.
Histology
• H &E showed some junctional activity over banal stromal naevus component.
• In some cases, junctional activity beyond stromal naevus component.
• FISH’ed because of ‘atypical’ junctional component.
Normal FISH pattern in a benign naevus with 2 copies of each signal.
Junctional component of ‘naevus’
Invasive MM after re-excising residual area
Outcomes
• 5 out of 7 ‘atypical’ junctional components were FISH ‘positive’: Classed as in-situ melanoma on morphological, architectural and FISH criteria, developing over naevus. The stromal naevus component in the 5 cases was FISH negative.
• 2 out of 7 were FISH ‘negative’: Designated as ‘atypical naevi’ with careful follow up.
Post-excision outcomes
• 3 cases of in-situ melanoma showed residual intraepithelial FISH positive cells after excision or original ‘naevus’.
Further service evaluation.
• Assessment of the post MMC bx after treatment of in-situ MM /C-MIN / atypical melanosis.
• Finding that FISH can pick out abnormal copy number in post MMC individual melanocytes in epithelium, along basal layer….helping in interpretation of bx.
FISHing expedition…
• Great for small volume tissue• Result is visual. • Correlate histology and molecular
phenotype. • Very useful -not miraculous.• Morphology is still important.• If the histology is atypical, a positive FISH
result is highly supportive, but a negative FISH result should not be taken as dismissal.
• Expensive….therefore should really use on ‘equivocal / ambiguous’ cases only.
Thanks