Lipofibromatosis: A Rare Diagnosis on Fine Needle Aspiration Cytology
Arti KHATRI1, Nidhi MAHAJAN1, Mamta SENGAR2, Anil AGARWAL3
1Departments of Pathology, Chacha Nehru Bal Chikitsalaya, Geeta Colony, DELHI, INDIA
2Departments of Pediatric Surgery, Chacha Nehru Bal Chikitsalaya, Geeta Colony, DELHI, INDIA
3Departments of Orthopaedics, Chacha Nehru Bal Chikitsalaya, Geeta Colony, DELHI, INDIA
Keywords: Lipofibromatosis, Cytology, Pediatric, Recurrence
Lipofibromatosis is a recently recognized slow growing rare pediatric tumor. Paucity of its cytological description in the literature leads to its pre
operative misdiagnosis and further incomplete management. A twelve-month-old female presented with a rapidly progressive mass in the right
thigh and buttock region. On examination, the mass was huge and involved the medial, posterior and lateral aspects of the thigh. The cytological
smears showed mature adipocytes with few spindled out cells. FNA was reported as a lipoma, corroborating with the radiological presumptive
diagnosis. However, histopathological and immunohistochemical features favoured a diagnosis of Lipofibromatosis. The cytological smears were
reviewed and a cyto-histo correlation was established. The diagnosis of Lipofibromatosis rests upon classical cytological features in a clinically
and radiologically suggestive picture. An early and accurate diagnosis if established can help the surgeon plan excision with wider margins as
incomplete excision is associated with a high rate of recurrence.
Lipofibromatosis (LF) is an uncommon pediatric soft
tissue tumour, more often seen in males (M: F -2.7:1) 1
It is usually seen from birth to childhood and presents as
a subcutaneous mass upto 5 cms in size 2
. The lesion is
known for its recurrence if excised incompletely, but no
metastasis however has been reported so far 1
. Due to
the rarity of the tumor, there is paucity of its cytological
description in the literature. We hereby present a twelvemonth-
old female child with a huge right gluteal and
thigh mass, together with the radiology, cytology and
A twelve-month-old girl presented with a rapidly
progressive painless mass over the right gluteal and upper
thigh region. The mass was seen at birth in the right
buttock and was of the size of a lemon to begin with;
however, it had rapidly grown over the last six months and
now extended over the thigh. The patient gave a history
of incision and drainage of that site in a private hospital
in view of it being reported as a gluteal abscess with mild
vascularity on Ultrasound. On examination, the mass was
diffusely involving the medial, posterior and lateral aspect
of the right upper thigh extending into the gluteal region,
measuring 17 x 14 cm with an ulcer on the overlying skin
(Figure ffigure1>1A). No thrill or bruit was palpated. The mass was firm to hard, immobile and non-tender. X-Ray (Figure
) and CT scan of the mass were acquired, both of which
suggested a poorly circumscribed thigh mass deep to the
muscles suggestive of an adipocytic lesion, possibly lipoma.
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|Figure 1: A) Clinical picture of
the right gluteal and thigh mass
with an area of skin ulceration.
B) Radiograph shows a large
radiolucent mass. Underlying
bone is not involved.
Fine needle aspiration cytology (FNAC) was done and
showed a moderately cellular lesion composed of large
fragments of mature adipose tissue admixed with singly
scattered and groups of plump to spindle cells (Figure
2A-C). No lipoblast was seen. No nuclear pleomorphism,
mitosis or necrosis was identified. In view of the cytological
features, possibility of a benign lesion of adipocytic origin
(lipoma) was suggested and an excision for histopathological
correlation was advised in view of the large size of the
swelling for further complete evaluation. Per operatively,
it was an ill- defined solid mass deep to the thigh and right
gluteal muscle but could be easily separated from the sciatic
nerve. Grossly, the mass was grey white, measuring 17 x 13
x 12 cm and partly covered by an elliptical skin flap which
showed a central ulceration (Figure 3A). The cut surface
was yellow and lobulated with no areas of haemorrhage and
necrosis (Figure 3B). Microscopic examination revealed
a well delineated lesion consisting of lobules of mature
adipose tissue with interlacing fibrous bands of variable
thickness (Figure 4A,B). The bands comprised bland
looking fibroblasts with minimal nuclear pleomorphism.
Interspersed in between the mature adipose tissue were few
lipoblast-like cells. No true lipoblast was seen. The lesion also showed few entrapped skeletal muscle bundles (Figure
4C). No mitotic figure/necrosis was seen. The mature
adipose tissue was seen to infiltrate the adjacent skeletal
muscle. The overlying skin and skin resected margins were
free of the lesion, with the lesion almost reaching up to the
deep resected plane. The lesion showed negative staining
for Desmin and PLAG-1 on immunohistochemistry. The diagnosis of LF was made. Cytology slides were reviewed
and cyto-histo correlation was established. Thus presence of
large fragments of adipose tissue, viable muscle fragments
in close proximity to the adipocytes (Figure 2B, inset),
and spindled out cells on cytological smears warranted a
diagnosis of LF. The patient did well post operatively and
there is no recurrence so far (follow up of 5 months).
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|Figure 2: A) Cytology smears showing moderate cellularity comprising large mature adipose tissue fragments (Giemsa; x100). B) Smears
showing bland spindle cell cluster closely associated with the adipocytes (black arrow) (Giemsa; x400). C) Showing a viable muscle
fragment in a lipidaceous background (black arrow) (Giemsa; x400).
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|Figure 3: A) Gross specimen
showing a well delineated mass
with an ulcer in the overlying
skin. B) Cut section is yellow,
lobulated and solid.
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|Figure 4: A) Microscopic section showing lobules of mature adipose tissue (H&E; x100). B) Section showing benign appearing spindled
out cells and skeletal muscle interspersed within these mature adipocytes (black arrow) (H&E; x100). C) Section showing high power
view of the skeletal muscle bundles (H&E; x100).
Lipofibromatosis was first described in the year 2000 by
Fetsch et al. in a series of 45 cases, which were previously
reported as infantile or juvenile fibromatosis of the nondesmoid
. This tumor presents as a slow growing illdefined
subcutaneous mass in the extremities, trunk, back
and head and neck region of children, usually not larger
than 5 cm 3
. Deepti AN et al. reported LF in the foot with
size of 10 cm 2
. A case of diffuse upper limb involvement
has been reported in a two-day-old male child but the size
of which has not been mentioned 4
The lesion is known to occur from birth to early second
decade of life but can also be seen congenitally. Though
the median age of presentation in the two large series is 1
year, the majority of the cases usually present by 3 years of
age and 18% of these lesions are congenital 3. It is more
commonly seen in boys with a male to female ratio of 2.7:1
and the majority of the case reports are from male patients
1. Two large series of LF have been published, one with
six cases, of which two were females, and the other with
20 cases, of which six were females 2,3. Our case was a
female and presented congenitally. Also, it is the largest LF
operated on and reported so far in the literature.
The etiopathogenesis of LF is still unclear. No recurrent
genetic alteration has been detected. Al-Ibraheemi et al. in
their study on 20 cases of LF found recurrent FN1-EGF gene
fusion in four of their cases. This genetic aberration was
found to be characteristic feature of calcifying aponeurotic
fibroma. Based on this, they suggested that some cases of
LF actually represent early stages of calcifying aponeurotic
fibroma with no calcification. Their study found 8 other
genetic fusions which are known to activate the PI3KAKT-
mTOR pathway 5. A single case report of LF has
also been reported with multiple congenital anomalies
such as trigonocephaly, cleft lip and palate and syndactyly
6. Our case had no other congenital anomaly. Molecular
studies were not performed as they were unavailable.
Radiological imaging can help distinguish LF from other
entities, though not always diagnostic. Ultrasound is
usually nonspecific. MRI is the imaging modality of choice,
which shows LF as a well-defined mass with hyperintense
signalling that is isointense to fat on T1- and T2- weighted
images. These signals however vary depending upon the
proportion of adipocytic and fibroblastic components.
Hence, MRI is only suggestive and therefore partially
helps in pre-operative planning. The cytological features of
this entity are not reported often in the literature and the definitive diagnosis rests upon histopathology. The tumor
is associated with high recurrence rates of about 72% 1.
Boss et al. reported a recurrence of 33% in its series of six
cases of LF 3. No metastasis however has been reported so
far. Thus, a pre-operative cytological diagnosis is essential
for management of these cases as complete surgical excision
with a wide margin ensures low recurrence.
The cytological indicators of LF are presence of skeletal
muscle fibres, mature adipose tissue and benign appearing
spindle cells clusters in close proximation. The background
may be lipidaceous or myxoid. A few stromal fragments
may also be noted. No true lipoblast is seen. There is absence
of nuclear pleomorphism, necrosis and mitosis. Grossly,
LF is unencapsulated with poorly defined margins. The
cut section is yellow with whitish streaks. The microscopic
sections show abundance of mature adipose tissue (>
50%) traversed by a fibroblastic component. The latter is
comprised of bland spindle shaped cells and sometimes may
show myxoid change. Small univacuolated cells, which are
actually degenerating adipocytes or lipid rich fibroblasts,
are seen at the interface of fibroblast and adipose tissue.
These may be mistaken for lipoblasts. No nuclear atypia or
necrosis is seen. Mitotic figures were not seen in our case
but have been reported by Fetsch et al. in one third of the
cases 1,4,6. Immunohistochemistry is neither specific
nor required. However, the cells may express CD 99, BCL
2, S-100, CD 34 and Actin. LF can be differentiated from
other adipocytic, myofibroblastic and fibroblastic lesions of
childhood clinically, cytologically and histopathologically
(Table I) 7-10. This differentiation is important in view
of the significantly different prognosis and management.
When incompletely excised, this tumor has a high rate of
local recurrence which may be destructive or obstructive
depending upon its site, making complete surgical removal
with wide margins imperative. Metastasis has not been
reported so far, though factors like congenital onset, male
gender and mitotic activity in the fibroblastic component
have been associated with recurrence 1.
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|Table I: Characteristics of the differential diagnosis of Lipofibromatosis.
Our experience with the current case has led to the
conclusion that Lipofibromatosis may be congenital, can
occur in females and can present as a large mass involving
the extremities. The diagnosis can be made with near
precision on FNAC if classical cytological features are
present along with clinical and radiological suspicion.
A pre-operative diagnosis of this rare entity can help the
surgeon plan complete resection with wider margins to
prevent future recurrence.
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