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Title	Lack of monosomy chromosome 3 in conjunctival melanoma and naevi
Abstract Nr.	132

Purpose	Monosomy of chromosome 3 has been established as an important prognostic factor for intraocular tumors, and is being used in practice. This study investigates monosomy 3 in conjunctival melanoma and naevi.
Methods	Paraffin embedded sections of 13 conjunctival melanomas, 11 conjunctival naevi and three samples of primary acquired melanosis (PAM) were investigated by fluorescence in situ hybridization (FISH) using a DNA-specific probe for the centromere region of chromosome 3. In addition, monosomy 3 was further assessed with FISH on nuclei, isolated from paraffin-embedded tissue and compared to the results of FISH on regular histological paraffin sections.
Results	Combining FISH on histological paraffin sections and on isolated nuclei showed no monosomy 3 in conjunctival melanoma or naevi. Of 13 conjunctival melanomas one sample could not be evaluated with FISH on whole sections, but satisfactory results were obtained on nuclear preparations. Although five melanoma samples seemed to show monosomy 3 when FISH was applied on sections, this was not confirmed on isolated nuclei preparations.
Conclusion	In difference with uveal melanoma where monosomy 3 is present in up to 60% of samples, conjunctival naevi and melanoma do not show monsomy 3. The high false-positive rate obtained with FISH on histological paraffin sections determines the necessity of using nuclear suspensions for monosomy studies.

Author 1

Last name	MISSOTTEN
Initials	GS
Department	Leiden University Medical Center, Nederland & Catholic University Leuven, België
City	Leiden - Leuven

Author 2

Last name	Maat
Initials	W
Department	Leiden University Medical Center, Nederland
City	Leiden

Author 3

Last name	Jordanova
Initials	JS
Department	Leiden University Medical Center, Nederland
City	Leiden

Author 4

Last name	De Keizer
Initials	RJ
Department	Leiden University Medical Center, Nederland & Antwerp University, België
City	Leiden - Antwerpen