ImmunoFISH Is a Reliable Technique for the Assessment of 1p and 19q Status in Oligodendrogliomas

OBJECTIVE To develop a new ImmunoFISH technique for the study of oligodendrogliomas by combining a standard immunohistochemical stain using MIB-1 antibody with a standard FISH technique using commercial 1p36 and 19q13 chromosomal probes. METHODS Validation was performed by two observers on a series of 36 pre-selected oligodendrogliomas and compared to the results previously determined by FISH alone. RESULTS The ImFISH technique is easy to perform and to analyze and is no more time-consuming than the usual FISH technique. Our results show that the inter-observer reliability of ImFISH is high (κ = 0.86 and 0.95 respectively for 1p and 19q). Compared to FISH, the ImFISH exhibits a very high sensitivity (∼100%) and specificity (∼90%) for 1p and/or 19q deleted cases. The sensitivity is high for normal cases (∼85%) and imbalanced cases (∼90%) with a specificity ranging between 50 and 85%. Finally, there were no significant differences between FISH and ImFISH results calculated on 60, 40 or 20 cells. CONCLUSION Our study demonstrates the reliability of the ImFISH technique in oligodendrogliomas and emphasizes its advantage in poorly cellular tumoral specimen.