hi I'm Jared gardener and I'm here today
with my dramatic pathology fellow dr.
Edie Fulton and Ed's picked out some
additional interesting cases today the
the entity we're going to talk about
today is called by a couple of different
names
it's inclusion body fibromatosis and the
other names it's known by are infantile
digital fibroma or infantile digital
fibromatosis like all things in soft
tissue pathology the multiple names are
kind of a mouthful and make make things
sound more confusing maybe than they are
this is a really neat entity because
it's got a unique clinical presentation
it usually occurs on the digits of
babies so either the toes of the fingers
and it has an interesting predilection
to the 2nd 3rd and 4th digits
particularly usually on the dorsal
aspect in the middle to the distal
portion of the digit and about 30% or so
of these are present at the time of
birth and the rest develop usually
within the first a year or so of life
and rarely they've been reported in
other sites away from the digits and
even in adults I've never seen that I've
only seen them on the digits of babies
but it's been reported the name tells
you what you're gonna expect to see here
inclusion body fibromatosis first of all
it's a fibroblastic proliferation that
it fills the dermis and sometimes
extends into the sub cutis when we go
down to higher power what we see are
fibroblasts that are running in these
fascicles fascicles that are kind of
weaving back and forth with one another
okay and so you can see where the name
fibromatosis comes from it's important
to remember this is not at all related
to desmoid fibromatosis or some of the
other fibromatosis that you hear about
and it's not related to palmar or
plantar fibromatosis which in my
experience usually occurs in adults and
is usually down deeper in the the soft
tissue of the hand the palm of the sole
and is attached to the underlying
tendons rather than centered in the
dermis like inclusion body fibromatosis
so it's important to to not get it
confused with those but you can see that
these are fascicles here and I think
I've got my condenser flipped so it
gives us refract I'll look I think it's
a nice way to see the architecture of
the cells okay so you can see they're
streaming along in these fascicles
nowhere near as broad and wide of
sicles as you'd see in Des Moines
fibromatosis and again Des Moines
fibromatosis rarely occurs on the hands
or feet rarely will occur in young kids
and almost never involves the dermis
unless it's part of a larger mass that's
pushing up and I have a video on desmoid
tumors desmoid fibromatosis I'll pop a
link up into the upper right hand corner
here so you can see that so you can see
that these are our fibroblasts and my
desmoid fibromatosis video actually also
has a discussion of how to tell
fibroblasts apart from say smooth muscle
cells so even though they again this is
not a desmoid tumors we're looking at
that video does have some helpful clues
about that so here's a real nice example
these streaming fascicles they're
streaming like like a school of fish all
swimming together all of these elongated
nuclei running in the same direction
there's pink collagen fibers in between
each cell which is a characteristic
feature of fibroblasts and even from
here you can already see look at this is
the key these are the inclusion bodies
these little bright red or pink globules
of actin filament that are condensed in
the cytoplasm of the of the fibroblasts
right next to the nucleus okay and even
though we say this is fibroblastic
actually if you do in a smooth muscle
actin stain you'll see the wispy tram
track pattern of actin staining that is
characteristic of Maia fibroblastic
processes in my opinion fibroblastic and
Maia fibroblastic entities in soft
tissue pathology have a lot of overlap
and I think fibroblast and Maya
fiberglass are closely related cells so
I don't make a huge point about
distinguishing between those two
phenotypes of cell when you have this
clinical history of a nodule on the
fingers or toes of a baby and you see
fascicles of bland fibroblastic spindle
cells and little inclusion bodies you're
done there's two in my opinion no
immunise things are needed this is the
diagnosis this is inclusion body
fibromatosis if you wanted to do a fancy
stain there are a few stains that will
stain and highlight these little these
little inclusion bodies there's a kind
of an old-school stain called phosphate
on zyk acid hematoxylin or pta h it will
highlight those little globules in a
dark purple color most labs that i've
ever worked at do not
have that stain available even because
it's kind of an older histochemical
technique you can also use the trichrome
stain which will highlight these bright
red in color and I think the mome at
stains supposedly will stain them pink
but I don't routinely use mo VAT
although it's a pretty stain I don't
usually use it in soft tissue pathology
personally and also if you use potassium
hydroxide to pretreat the tissue these
globules will also stain with smooth
muscle actin immuno stain at least
that's what the WH o book says I'm not
exactly sure how you do potassium
hydroxide pretreatment but that's what
the books say in in my practice I have
the I only see these occasionally and I
think they're almost always diagnoseable
on H and E only without any special
stains they're quite beautiful to look
at and they are benign but they do have
a tendency for local recurrence some of
the early literature suggested that they
had a 60 or 70 percent recurrence rate
but if you completely excised them the
rate is probably lower and and also in
my experience a lot of the soft tissue
tumors even benign ones on the hands and
feet have a higher tendency for local
recurrence and I personally believe
that's because we are surgeons are often
a lot more conservative when they're
removing things on the hands and feet
and there's a very limited amount of
space there between the skin the sub
cutest the underlying of tendons and
soft tissues in muscles and so it's
understandable that things will grow
back more often there because especially
kind of infiltrative things because it's
harder to get the entire lesion out
without you know potentially
compromising other structures and so I
think surgeons are a little bit more
cautious there and rightfully so so it
does recur locally but it's not an
aggressive lesion and it's not malignant
so again it's important to distinguish
this safe from desmoid tumor and with
this clinical history with these
inclusion bodies and with the lesion
being centered in the dermis you should
basically never have that problem
because desmoid tumors when desmoid
fibromatosis wouldn't look like this
so again some areas here you can see
some of the fascicle growth here's a
fascicle kind of pushing down into the
sub cutis but up in the dermis here it's
not quite as specific an still see those
nice little
inclusion bodies which are the hallmark
of this disease all right now I'm going
to show you one additional case that is
less vesicular and might at first glance
be harder to recognize here's a little
papule from the toe or I think this was
from the finger if I recall of a young
baby a one-year-old so again right away
there's a limited number of things I'm
gonna be thinking about in my
differential for for a skin nodule on
the finger of a baby and even though
this doesn't have the you can see here
again with the condenser flipped you can
see that there are spindle cells with
intervening collagen see those those
kind of refract I'll lines standing out
are the pink collagen bundles being
deposited by the fibroblasts which of
the paler areas that you're seeing there
so that's how you can tell apart what
the the cells are and the intervening
collagen that they make and that's a
characteristic of both fibroblasts of
Maya fibroblasts that they'll lay down
collagen in between them so when you go
closer you can see these are kind of
plump spindled fibroblasts or Maya
fibroblasts they don't really look
nearly as fascicular as the original
case I showed you but with a little bit
of searching you can see that they do
they're a little bit more subtle here
there's a red blood cell there but you
can see they're there they're even right
there those are the inclusion bodies so
if you look around a little bit and
there's a couple more over here so the
the fibroblastic fascicles are not
always quite so dramatic and these cells
are more plump and kind of have pale
chromatin and central nucleoli again to
my mind this is what Maya fiberglass
kind of looked like and so I think we
kind of have an overlap between Maya
fibroblasts and fibroblasts type cells
here in this lesion and again here you
can see that it's certainly there's a
spindle cell proliferation of the dermis
that is nowhere near as organized into
fascicles but looking around and finding
those inclusion bodies is going to be
the key to recognizing this entity so I
hope you've enjoyed a quick visit with
our friend inclusion body fibromatosis
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