Keywords
chondroblastic osteosarcoma - occipital bone - skull base - computed tomography -
magnetic resonance imaging
Introduction
Osteosarcoma (OS) develops most frequently in the extremities, and it is the most
common histologic form of the primary bone cancers.[1]
[2] Head and neck OSs are rare, comprising only 6 to 10% of all OSs.[3]
[4] They typically present in the third or fourth decade of life and comprise only 1%
of all pediatric head and neck malignancies. The most common craniofacial sites affected
by OSs are the mandible and maxilla, followed by the calvaria and then the skull base.[4]
[5]
[6] On cytology, OS can be divided into several pathologic types, including the pleomorphic,
epithelioid, chondroblastic, small cell, mixed, and osteoclast-like giant cell types.[6] In head and neck OSs, the chondroblastic type occurs most frequently.[7]
Skull base OSs can be challenging to resect and an aggressive surgical approach can
result in poor cosmetic outcome.[8] Imaging plays a crucial role in the diagnosis of each subtype of OS and ultimately
in patients' survival because the diagnosis is based on a combination of histopathologic
and imaging features. The therapeutic options and prognoses for different types of
OS differ from each other, so correct diagnosis is essential.[9]
[10] Magnetic resonance imaging (MRI) or computed tomographic (CT) scan should be used
to assess the extent of the primary tumor.[11]
In this case report, we describe a pediatric patient of occipital OS of the chondroblastic
type. The chondroblastic type of OS has an exceedingly poor outcome.[12] However, the detailed imaging description of such cases have not been reported in
the previous literatures. We present the CT, MRI, and enhanced MRI features of this
case, followed by a brief review of the related cases reported in the previous literatures
Case Report
A 9-year-old boy was admitted to our hospital with a major complaint of a growing
mass on his head. Physical examination found a firm and tough mass on the right occipital
that showed no tenderness upon palpation. CT scan showed the right occipital bone
to be irregularly thickened with fluffy and cloudy calcification, with a mass deriving
from the internal occipital protuberance extending toward the basilar part of the
occipital bone, invading the neighboring jugular foramen, the sublingual neural tube,
and the mamillary process. On MRI, the lesion was 4.5- × 5.5- × 6.5-cm in size with
calcifications areas of hypointensity in T1- and heterogeneous in T2-weighted series.
Contrast MRI showed peripheral and septal enhancement in the interior side of the
tumor ([Fig. 1]). Significant mass effect was present, distorting the cerebellar hemisphere, pons,
and the forth ventricle, which led to hydrocephalus, and the oppression of the sigmoid
sinus and the transverse sinus. Histopathology examination reported lace-like osteoid
material abutting the neoplastic cells ([Fig. 2]), corresponding to the features of chondroblastic OS, and occipital bone chondroblastic
OS was the final definitive diagnosis. A subtotal resection of the tumor was performed
followed by radiation therapy. The patient died after half a year of local recurrence.
Fig. 1 (A) Computed tomography of the skull shows fluffy calcification. (B) T1-weighted image shows a 4- × 8- × 10-cm mass lesion, isointense to the skull.
(C, D) The mass is hypointense in most areas in the T2-weighted series, with focal high
signals in the T2-weighted series and reduced signal in FLAIR series.(E) In Gd-enhanced MRI, most areas show no enhancement or heterogeneous enhancement,
with peripheral and atypical septal enhancement on the coronal plane (white arrows).
(F) No hyperintensity was observed in both intra- and peritumoral areas in the DWI series.
Fig. 2 Histopathologic examination (hematoxylin and eosin, ×200) shows lace-like osteoid
material abutting the neoplastic cells.
Discussion
Craniofacial OSs are rare. They typically present in the third or fourth decade of
life, account for fewer than 5% of OSs in children, and comprise only 1% of all pediatric
head and neck malignancies. The most common craniofacial sites are the mandible and
maxilla, followed by the calvaria and then the skull base.[13]
[14]
[15] Our case in the right occipital bone of skull base is a very rare location. A search
of the English language literature revealed 22 cranial OSs previously reported in
children ([Table 1]): 12 calvarial tumors and 10 tumors of the skull base. The mean age of the pediatric
patients with cranial OS was 12.2 years old in this table. The patient in our case
suffered at a younger age. On cytology, OS can be divided into pleomorphic, epithelioid,
chondroblastic, small cell, mixed, and osteoclast-like giant cell types.[6] Our case is a chondroblastic subtype, which occurs most frequently in head and neck
OSs.
Table 1
Summary of previously reported cases of calvarial and skull base osteosarcomas in
pediatric patients
|
Author and year
|
Age at diagnosis
|
Location
|
Extent of resection
|
Adjuvant therapy
|
Follow-up
|
Outcome
|
|
Garland, 1945
|
17, M
|
Occipital
|
NR
|
RT
|
NR
|
NR
|
|
Reddy et al, 1973
|
8, F
|
Occipital
|
Biopsy
|
RT
|
NR
|
Dead, progressive disease
|
|
Goodman and McMaster, 1976
|
15, F
|
Parietal-occipital
|
NR
|
Chemotherapy and RT
|
6
|
Alive, disease free
|
|
Wang et al, 1981
|
17, M
|
Frontal-parietal-occipital
|
NR
|
RT
|
6
|
Dead, progressive disease
|
|
Benson et al, 1984
|
11, M
|
Frontal
|
NR
|
Chemotherapy
|
12
|
Alive, disease status
|
|
Sundaresan et al, 1985
|
11, M
13, F
|
Parietal
Skull base
|
STR
STR
|
Chemotherapy
Chemotherapy
|
36
66
|
Alive, progressive disease
Alive, disease free
|
|
Kornreich et al, 1988
|
12, F
|
Parietal
|
NR
|
Chemotherapy
|
144
|
Alive, disease free
|
|
Mark et al, 1991
|
14, M
|
Anterior skull base
|
NR
|
Chemotherapy and RT
|
12
|
Dead, progressive disease
|
|
Shramek et al, 1992
|
8, M
|
Parietal-occipital
|
GTR
|
Chemotherapy and RT
|
16
|
Alive, progressive disease
|
|
Salvati et al., 1993
|
11, M
|
Frontal-temporal
|
STR
|
RT
|
9
|
Dead, progressive disease
|
|
Chander et al, 2003
|
15, F
|
Frontal
|
GTR
|
NR
|
NR
|
NR
|
|
Author and Year
|
Age at diagnosis
|
Location
|
Extent of resection
|
Adjuvant therapy
|
Follow-up
|
Outcome
|
|
Ellison et al, 1996
|
11, F
|
Skull base
|
STR
|
Chemotherapy and RT
|
NR
|
NR
|
|
Gadwal et al, 2001
|
9, M
1, M
|
Sphenoid
Sphenoid
|
NR
NR
|
RT
NR
|
9
NR
|
Dead, progressive disease
NR
|
|
Chennupati et al, 2008
|
14, F
|
Skull base
|
Biopsy
|
Chemotherapy and RT
|
12
|
Alive, progressive disease
|
|
Kirby et al, 2011
|
16, M
|
Parietal
|
GTR
|
Chemotherapy
|
5
|
Alive, disease free
|
|
Oakley et al, 2011
|
15, M
|
Anterior skull base
|
GTR
|
Chemotherapy
|
NR
|
NR
|
|
Ohno et al, 2011
|
14, F
|
Anterior skull base
|
STR
|
Chemotherapy
|
26
|
Dead, progressive disease
|
|
Meel et al, 2012
|
10, M
|
Sphenoid
|
Biopsy
|
Chemotherapy and RT
|
18
|
alive, disease free
|
|
Caroline et al, 2014
|
14, M
12, M
|
Parietal skull base
|
GTR
GTR
|
Chemotherapy
Chemotherapy
|
16
12
|
Alive, disease free
|
|
He et al, 2016
|
9, M
|
Occipital
|
STR
|
Chemotherapy and RT
|
6
|
Dead, progressive disease
|
Abbreviations: GTR, gross total resection; NR, not reported; RT, radiation therapy;
STR, subtotal resection.
The etiology of OS is unknown, but the major risk factors for development of OS in
craniofacial bones may be similar to those of the long skeletal bones, consisting
of exposure to radiation, retinoblastoma, Li-Fraumeni syndrome, and Paget's disease.
The skull is a favored site for OS arising out of Paget's disease. Other bone abnormalities,
such as fibrous dysplasia, multiple osteochondromatosis, chronic osteomyelitis, myositis
ossificans, and trauma, have also been proposed as risk factors.[7]
[15]
[16] The presenting symptoms varied with the location of the tumors. The maxillary or
cranial lesions usually produced no pain, which was in accordance with our case; however,
mandibular tumors frequently presented with focal painful swelling.[17]
[18] Other common presenting symptoms include headache, cranial nerve palsies, exophthalmos,
and visual impairment due to different location of the tumor.[5]
[13]
CT best demonstrates tumor mineralization, especially when minimal, and it is usually
able to demonstrate tumor extension into the soft tissues. Hemorrhage, necrosis, and
unmineralized, chondroblastic, or fibroblastic components of the tumor will appear
as areas of low attenuation on CT if present. Unlike any other conventional OSs, we
see fluffy calcification in our case, and we believe it is a characteristic of OS.
The osteoblastic subtype is most common with nearly 90% containing variable amounts
of cloudlike opacities.[19] Bose[20] reported an osteoblastic OS that appears as a large soft tissue density mass with
a few bony densities. Compared with our case, the soft tissue mass is prominent and
the calcification is less and diffuse.
MRI is the preferred modality for locally staging OS, and it should be performed before
percutaneous biopsy because it can help identify areas of viable tumor and mineralized
matrix. In our case of gadolinium (Gd)–enhanced MRI, we found no enhancement or heterogeneous
enhancement in most areas of the tumor, with septonodular and rim enhancement, which
is in in accordance with the current literature. Areas that demonstrate either a heterogeneous
enhancement pattern or lack enhancement are the preferred sites for biopsy because
they are more likely to contain both chondroid and osteoid elements that are necessary
for the correct diagnosis.[21]
[22] Chondrosarcomas shows similar image characteristic, but they occur in an older age
with a mean age of 57 years old. DWI can also help identify chondroblastic OS. Chondroblastic
OSs also have significantly higher minimum and maximum apparent diffusion coefficient
(ADC) values compared with other conventional OS subtypes, but they have a lower minimum
ADC and similar maximum ADC value compared with chondrosarcoma.[23]
Skull base OSs can be challenging to resect, and an aggressive surgical approach can
result in poor cosmetic outcome. Thus, skull base tumors have a poorer prognosis than
mandibular or maxillary tumors.[3] Complete surgical excision is the mainstay of treatment of the primary tumor. Local
recurrence is the main reason of treatment failure and mortality in head and neck
OSs. Positive margins and a high tumor grade correlate with a statistically significant
decrease in survival.[11] In our case, the tumor could not be completely removed because it invades significant
neighboring bone structures, including the jugular foreman and the sublingual neural
tube. The patient died after 6 months as a result of local recurrence.
In summary, chondroblastic OS has been shown to be associated with a poor preoperative
chemotherapy response and has a worse prognosis than other variants.[24] However, this subtype has some particular image characteristic, which helps surgeons
identify before surgery and set early therapeutic regimens.
