An 18- month- old girl was brought with complaints of mild grade intermittent
fever associated with cough and breathlessness for the previous three days.
The parents gave history of similar complaints which had occurred intermittently
over the previous 3-4 months. They also gave history of treatment with antibiotics
on a number of occasions.
On examination she was febrile and her chest examination revealed decreased
air entry on the right side.
The haemogram was unremarkable. Peripheral smear was negative for malarial parasites
and widal test was negative.
A frontal chest radiograph was obtained as a routine investigation.
Fig 1
Radiological Findings
:
The chest radiograph reveals a large soft tissue mass in the right chest with
well-defined medial border which was broad based towards the pleura and occupies
the right middle and lower zones laterally. There was no evidence of calcification
or cavitation within the mass.
A previous chest radiographs showed a similar lesion which had not changed in
size for the past 3 months.
An ultrasonogram and CT scan of the chest were obtained.
Fig 2
Fig 3
Fig 4
Fig 5
Fig 6
Fig 7
The ultrasound of the chest reveals a hyperechoic nonvascular mass lesion in
the pleural cavity compressing the adjacent lung. There is no pleural effusion
or air bronchogram associated.
CT scan of the chest shows a mass of fat attenuation value, approximately 9x5.4
cms in size situated in the right hemithorax appearing pleural/extrapleural
in location. Atelectasis of the underlying lung parenchyma is seen with shift
of the mediastinum to the left. The tracheo-bronchial tree is normal. There
was no other abnormality seen and the left side of the chest was normal.
Based on the above radiological findings, a diagnosis of lipoblastoma was made.
A liposarcoma was the other differential diagnosis.
The patient was operated and the whole tumour was excised successfully with
an intercostal approach.
The histopathological diagnosis was lipoblastoma.
Discussion
Lipoblastomas are rare benign mesenchymal tumors
of embryonic white fat occurring in infancy and early childhood. Age at presentation
is usually less than 5 yrs with a slight male preponderance. Among the soft
tissue tumors in the first year of life it occurs with a frequency of about
3%. The main clinical picture is of a rapidly growing mass in a peripheral location,
mainly the extremities (70%). It can arise within soft tissue. Lipoblastomas
can arise in the neck, mediastinum, chest wall, omentum, retroperitoneum and
intrascrotal locations. The lipoblastoma arising from chest wall is rare and
frequently has extrathoracic component.
The tumor presents in two forms: a circumscribed lesion which is situated superficially
(lipoblastoma) and a less common multicentric, diffuse form which arises in
deeper tissue (lipoblastomatosis).
This tumor is well-encapsulated containing fetal-embryonal fat and loose fibrovascular
connective tissue. Histologically, the differentiation of lipoblastoma from
liposarcoma, especially its myxoid variant, may be difficult. However these
benign immature adipocytic neoplasms have a more uniform growth pattern and
typically show striking lobulation. Although lipoblasts in different stages
of maturation are present in a lipoblastoma, there is no nuclear atypia or pleomorphism,
in contrast to that seen, at least focally, in liposarcoma. Lipoblasts have
the capacity for differentiation.
A breakdown in the long arm of chromosome eight (8q11-13) is a consistent finding
in this tumor.
In younger patients, when they arise from the neck or mediastinum, these tumors
can grow rapidly leading to recurrent respiratory tract infection or asphyxia,
occasionally causing death if not removed.
Radiographically, lipoblastoma presents as a non-specific soft-tissue density
mass.
Ultrasound helps to differentiate between a solid, cystic or a fat containing
mass.
CT allows identification of the fatty component and prominent intratumoral stranding,
but may not allow differentiation between the various adipose tissue tumors.
Both Ct and MRI suggest the extent and origin of the tumor.
On MRI lipoblastomas show a bright signal on both T1 and T2 weighted images.
A case of lipoblastoma which was hypointense to fat on T1 and having high signal
on T2 has been described, this atypical MR manifestastion was ascribed to the
presence of immature fat and myxoid tissue, intratumoral infarction and extensive
mucoid and cystic dgeneration.
The main differential diagnosis is from a liposarcoma which may have an identical
clinical and radiological presentation but is extremely rare in patients under
10 yrs of age.
It is recommended a complete but conservative excision of the tumor because
there is a natural tendency for involution although in the first year of life
a recurrence rate of 15% is described.
Metastasis have not been reported.
Prognosis is usually excellent.
In the present case ultrasound suggested us the fatty nature of the tumor which
was confirmed by CT, CT also suggested the origin and extent of the tumor thus
aiding the surgeons for a complete and successful removal.
