Sabato 27 ottobre 2012 - Pacini Editore

296
Histologic quality control of frozen samples using
matching FFPE tissue – preliminary results of our
institutional biobank
E. Mattioli1 , E. Foglia Manzillo1 , V. Rubini1 , F. Palma2 , A. Paradiso3
1 2
, G. Simone
1 2 Institutional BioBank at Anatomic Pathology Unit; Anatomic Pathology
Unit; 3 Scientific Management National Cancer Research Centre, Istituto
Tumori “Giovanni Paolo II”
Background. Biobanking is an emerging discipline which is becoming
more and more important in the contemporary research
scenario, as it is aimed at providing high quality samples (particularly
frozen ones) for biomolecular investigation. Integral part of
biobanking operations are tissue quality control (QC) procedures,
which verify and assure the adequacy of the collected samples
for research purposes 1-4 . Pathologists are particularly involved
in histological QC, which verifies that the banked samples are
representative of the whole lesion and are suitable for research
purposes, according to their pathological attributes. At our
Institution, we perform histological QC procedures by evaluating
critical immuno-morphological features (tumor cellularity,
amount of necrosis, inflammatory infiltrate, fibrosis and nonneoplastic
tissue components, proliferative index) not only on
the frozen biobank samples, but also on matching formalin-fixed,
paraffin-embedded (FFPE) material, which is easier to handle
and provides better morphological detail. Aim of this study was
to verify the concordance of those features on sections from the
frozen aliquots and from the corresponding paraffin tissue blocks.
Materials and methods. At our Pathology Department, as a
routine procedure, each biobank-dedicated tissue sample is cut in
two “mirror-matching halves”: one half is reduced into aliquotes,
which are weighed and frozen; the other half is sent to routine histological
processing to prepare a “specular” FFPE tissue block. 15
consecutive breast cancer cases from our Institutional Biobank were
considered for this study. For each case, multiple sections were cut
from one frozen aliquot and from the specular FFPE block; critical
parameters (percentage of tumor cells, MIB-1 proliferative index)
were then evaluated on both frozen and paraffin sections.
Results. The comparison of frozen aliquots with specular FFPE
tissue showed a variable degree of discrepancy, due to the intrinsic
heterogeneity of tumor tissue (Fig. 1). Predictably, the
fraction of concordant cases significantly varied according to the
stringency of the discrepancy threshold chosen (Tab. I). As for
the percentage of neoplastic cells, 60% of cases (9/15) showed
concordant values between frozen and paraffin sections when a
10% deviation was allowed; raising the allowed deviation to 20%
Fig. 1. heterogeneous miB-1 labeling in one of our breast cancer
cases.
CONGRESSO aNNualE di aNatOmia patOlOGiCa SiapEC – iap • fiRENzE, 25-27 OttOBRE 2012
Tab. I. figures of tumor cellularity and miB-1 labeling of each couple
of samples (frozen and ffpE) are shown on the left side. Concordance
percentages for different discrepancy thresholds are shown on the right
side. Colors highlight different discrepancy thresholds.
Case ID Tumor
cellularity
MIB-1 labeling
142/12 frozen 50% 10%
142/12 ffpE 50% 13%
139/12 frozen 35% 17%
139/12 ffpE 35% 25%
135/12 frozen 20% 2%
135/12 ffpE 20% 3%
100/12 frozen 20% 60%
100/12 ffpE 25% 40%
133/12 frozen 60% 90%
133/12 ffpE 70% 85%
99/12 frozen 65% 50%
99/12 ffpE 75% 38%
87/12 frozen 85% 28%
87/12 ffpE 80% 15%
92/12 frozen 60% 7%
92/12 ffpE 70% 17%
95/12 frozen 70% 15%
95/12 ffpE 70% 10%
105/12 frozen 55% 35%
105/12 ffpE 70% 18%
144/12 frozen 50% 10%
144/12 ffpE 70% 15%
97/12 frozen 60% 12%
97/12 ffpE 40% 7%
132/12 frozen 38% 5%
132/12 ffpE 75% 15%
145/12 frozen 30% 20%
145/12 ffpE 55% 20%
94/12 frozen 40% 50%
94/12 ffpE 80% 40%
Concordance rates
tumor cellularity
- with a 10% discrepancy 60% (9/15)
- with a 15% discrepancy 66,7% (10/15)
- with a 20% discrepancy
miB-1 labeling index
80% (12/15)
- with a 5% discrepancy 40% (6/15)
- with a 10% discrepancy 66,7% (10/15)
- with a 15% discrepancy 86,7% (13/15)
brought the concordance fraction up to 80% (12/15). As for the
proliferative index, only 40% of cases (6/15) showed concordant
results when allowing a strict 5% discrepancy between frozen
aliquots and specular FFPE tissue, while concordance raised to
86.7% (13/15 cases) when tolerating a 15% deviation.