Annals of Diagnostic Paediatric Pathology

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Fig. 11 International Neuroblastoma Pathology Classification (INPC) (revised form). Morphological and prognostic categories. FH: favorable histology; UH:
unfavorable histology; GNBn: ganglioneuroblastoma, nodular; MKI: mitosis-karyorrhexis index. The prognostic categorization of GNBn is performed by
evaluating the neuroblastomatous component in the nodule(s) according to the criteria for neuroblastomas (modified from Peuchmaur et al., 2003).
Microscopical evaluation. The pathologist should not only
analyze morphology and MKI for the histoprognostic classification,
but also use the microscope for estimation of the tumor
cell content in the material designed for biological investigations.
Thus, microscoping a paraffin section from the tissue
sample which was used for imprinting prior to fixation,
will provide important information about the possible percentage
of tumor cells, non-tumor cells (e.g. lymphocytes or
stroma) and necrosis which might influence the representativity
of the imprint. A microscopic analysis of the tumor cell content
performed on frozen sections from the material which is
intended to be used e.g. for PCR of the 1p36.3 region, is even
more demanded because the correct interpretation of the PCR
result requires a tumor cell content of at least 70%.
It is obvious that the pathologist who is in charge of
handling samples from neuroblastic tumors, plays a central
role in providing adequate material for biological analyses.
Prognostic categorization by INPC and biological
markers – competing or complementary systems
It has been known for many years that MYCN amplification
in neuroblastomas is a strong indicator of aggressive tumor
behavior [4], and often associated with undifferentiated morphology
and increased MKI [27]. One might therefore be
tempted to ask whether the histoprognostic categorization provided
by the INPC could be replaced by the analysis of MYCN.
The correlation between INPC categorization and
MYCN status was investigated by Goto et al. [8] in a large
cohort of 628 patients with neuroblastic tumors. As expected,
97,7% of tumors with favorable histology (FH) were MYCN
non-amplified, while 93,2% of MYCN amplified tumors
showed an unfavorable histology (UH). However, the comparison
of MYCN status and INPC categories revealed a third
and surprisingly large group of tumors with UH but without
MYCN amplification. As shown in Fig. 12, the prognosis of
this group was intermediate to FH/non-amplified and UH/
amplified tumors, and the difference in EFS between all three
groups was statistically significant.
The majority of UH, non-amplified tumors were observed
at stage 3 and 4 in children older than one year. The
results of this investigation demonstrate that the
histoprognostic INPC categorization is able to identify a substantial
number of patients who, in spite of normal MYCN
status, belong to a group of inferior prognosis, and it appears
relevant to ask whether this category of patients should be
offered a modified form of therapy.
Further support to this notion comes from the recently
completed histopathological review of 124 stage 2A and 2B
MYCN non-amplified trial patients who were treated with
surgery alone according to the LNESG (Localised Neuroblastoma
European Study Group) protocol 94.01 (Navarro et al.,
in preparation). The review was performed according to the
INPC by the seven members of the SIOP European Neuroblastoma
(SIOPEN) Pathology Reference Panel (Gabriele
Amann, Klaus Beiske, Catherine Cullinane, Emanuele
D’Amore, Claudio Gambini, Sam Navarro, Michel
Peuchmaur), and assigned 20% of these MYCN-negative tumors
to the unfavorable category. The difference in event free
and overall survival between the favorable and unfavorable
subset was statistically significant and underlines the importance
of the INPC as a valuable tool for prognostic categorization
of localized, MYCN non-amplified tumors.
In the forthcoming LNESG2 study, these results have
already influenced the therapeutic design in case of relapse of
the localized tumor. It has been decided that the relapse will