Invasive breast carcinoma - IARC

Fig. 2.15 Mucinous carcinoma with infiltrative
invasive pattern. Irregular glands lined by cells
with malignant features infiltrate the stroma.
A
Fig. 2.16 Mucinous adenocarcinoma with expansile invasive pattern. A Note the complex glandular proliferation.
B The glands are lined by cells that have highly atypical nuclei and some intracytoplasmic
m u c i n .
B
pling of all macroscopically suspicious
areas has been recommended.
Histopathology
In the absence of obvious infiltration of the
s t roma, invasion is assumed if there are
complex papillary areas or back-to-back
glands lined by malignant-appearing cells
with little or no discernible intervening
s t roma. To qualify as frankly invasive,
such areas should be at least 10 mm 2 a n d
at least 3 mm in each of 2 linear dimensions
{1613}. Altern a t i v e l y, invasion may
be in the form of infiltrative glands, tubules,
cords or cell nests. The stroma may
resemble ovarian stroma or be desmoplastic.
In most cases there are also are a s
that are benign or borderline in a p p e a-
rance {1147,1150,1228,2047,2401}. R a rel
y, mucinous tumours contain areas of mucinous
adenofibroma with malignant epithelial
cells and foci of stromal invasion.
Differential diagnosis
The most important differential diagnosis
of mucinous ovarian carcinoma is with
metastatic mucinous carcinoma that may
present clinically as a primary ovarian
tumour. Most of these originate in the
large intestine, appendix, pancreas, biliary
tract, stomach or cervix {237,639,
1587,1703,2377,2406,3200,3221}. Since
this problem has been emphasized relatively
recently, it is likely that early reports
of the histological appearance and
behaviour of ovarian mucinous carcinomas
have been contaminated by metastatic
carcinomas masquerading as prim
a ry ovarian neoplasms (see Ta b l e
2.03). Common features that favour a primary
mucinous carcinoma are an expansile
pattern of invasion and a complex
papillary pattern {1614}. Common features
favouring a metastatic mucinous
carcinoma are bilaterality, a multinodular
growth pattern microscopically, histological
surface involvement by epithelial
cells (surface implants) and vascular
space invasion {1614}.
Somatic genetics
Tumour heterogeneity is common and
p robably is a reflection of the pro g re s s i o n
f rom benign to malignant neoplasia that
occurs in the development of mucinous
c a rc i n o m a s. Recent studies strongly suggest
that in the sequence of malignant
t r a n s f o rmation from benign and bord e r-
line mucinous tumours to infiltrative carc i-
noma intraepithelial (non-invasive) carc i-
nomas and carcinomas with purely expansile
(not obvious) invasion re p re s e n t
transitional stages of mucinous carc i n o-
genesis {1613}. This hypothesis is a l s o
s u p p o rted by recent molecular studies of
genetic alterations in mucinous t u m o u r s
{591,964,1755,1891}. An increasing frequency
of codon 12/13 K R A S m u t a t i o n s
in benign, borderline and carc i n o m a t o u s
mucinous ovarian tumours has been
re p o rted supporting the viewpoint that
K R A S mutational activation is an early
event in mucinous ovarian tumorigenesis.
Mucinous borderline tumours have a
higher frequency of K R A S mutations than
that of mucinous cystadenomas but a
lower rate than that of mucinous carc i n o-
mas {591,1755,1891}. Using micro d i s-
section, the same K R A S mutation has
been detected in separate areas exhibiting
diff e rent histological grades within the
same neoplasm {591}.
Prognosis and predictive factors
Clinical criteria
Stage I mucinous carcinomas have an
excellent prognosis. However, the prognosis
in cases with extraovarian spread
is very poor {1076,1228,1458,1613,2377,
2401,3069}.
Histopathological criteria
With the exception of one recent series
{3769}, grading of mucinous carc i n o m a s
has not been shown to be predictive of
behaviour or response to therapy independent
of the surgical stage {1076,
1228,1458,1613,2377,3069}. Infiltrative
s t romal invasion proved to be biologically
m o re aggressive than expansile invasion.
If individual invasive foci are all less than
10 mm 2 , they have been termed "micro i n-
vasive," and cases with this finding have
had a favourable outcome {1453,1613,
1 9 8 7 , 2 0 4 7 , 2 4 0 1 , 2 7 1 3 } .
Mucinous borderline tumour,
intestinal type
Definition
Ovarian tumours of low malignant potential
exhibiting an epithelial proliferation of
mucinous type cells greater than that
seen in their benign counterparts but
without evidence of stromal invasion. The
epithelial component resembles intestinal
epithelium, almost always contains
goblet cells, usually contains neuroendocrine
cells and rarely contains Paneth
cells.
Synonyms
Mucinous tumour of low malignant potential,
intestinal type; mucinous tumour of
borderline malignancy, intestinal type.
Epidemiology
These account for 85-90% of mucinous
borderline tumours.
Macroscopy
Mucinous borderline tumours of intestinal
type are bilateral in approximately 5% of
cases and usually are large, multilocular
or unilocular cystic masses containing
w a t e ry or viscous mucoid material.
Surface epithelial-stromal tumours 125