1 FEMORAL PAROSTEAL OSTEOSARCOMA METASTASE TO THE LUNG
A Case Report * I.P. Dharmawan ** A.A.Gede Yuda Asmara
INTRODUCTION
Parosteal osteosarcoma (POS), or juxtacortical osteosarcoma (JCO), is a rare
anatomical and clinical variant of osteosarcoma (1). POS is a slow-growing tumor which
originates from the outer layer of the periosteum and represents 65% of surface
osteosarcomas and approximately for 4,8% of all osteosarcomas. Unlike conventional
osteosarcomas, it involves an older age group typically in the 3rd and 4th decades of life and shows a slight female predilection (2). The tumor is characterized by its bland microscopic
morphology, prone to be misdiagnosed as other benign tumors. In the absence of
dedifferentiation, the prognosis is generally better than that of conventional osteosarcoma (3).
The tumor is usually located at the posterior aspect of the distal femur in about 70%
of cases, followed by the proximal tibia and proximal humerus. Rare locations, including
cranial, mandible, rib, clavicle, and tarsal bone, have also been reported (3).
Patients usually report a painless mass lasting for years, with decreased range of
movement of the adjacent joint. Dull pain and local tenderness are the second most common
symptoms. The protracted clinical behavior is an important feature distinguishing parosteal
osteosarcoma from other diseases of similar locations such as myositis ossificans and
high-grade surface osteosarcoma, which usually have a more rapid onset (3).
CASE AND METHOD
Male, 31 years old with chief complained pain on his right thigh since 2 years prior
admission. The pain come and goes, getting worse in night. Patient also complained lump on
his right knee since 8 months ago increasing size as time goes. Difficulty of breathing also
felled by the patient since 3 weeks prior to admission. Patient can not do normal activities
without pain. Loss of body weight and fever also complained, chronic chough negative.
History of trauma negative and all ready done open biopsy on January 2014 at Sanglah
Hospital with result Parosteal Osteosarcoma. No Family history who complained tumor.
From physical examination we found mass at distal posteromedial side of right thigh without
2 surrounding tissue with ill defined margin without tenderness. AVN distal is normal active
ROM of genu and ankle is normal. From X Ray femur AP/lateral and genu AP/lateral we
found bone tumor on the distal femur involve methaphyseal region with irregular pattern of
mineralization and the periphery of the tumor and less radiodense than the center. From Chest
X ray AP/lateral we found tumors mass multiple discrete nodules that spread throughout the
lung. Patient already done open biopsy on January 2014 at Sanglah Hospital with result
Parosteal Osteosarcoma. Patient refused to take any action.
3 Picture 2. X Ray femur AP/lateral and genu AP/lateral we found bone tumor on the distal femur involve methaphyseal region with irregular pattern of mineralization and the periphery
4 Picture 3. From Chest X ray AP/lateral we found tumors mass multiple discrete nodules that spread throughout the lung.
5 Picture 5. Tumor tissue composed of cells of osteoblast malignant fibroblastic partially formed osteoid matrix with parallel pattern. Malignant osteoblasts cells are round to spindle
with hipercromatic core and irregular nuclear membrane,
DISCUSSION
Parosteal osteosarcoma is a rare malignant bone tumor arising from the bone cortical
6 the long bones near the knee joint. Patients usually report a slow-growing mass for years. The
tumor is characterized by its bland microscopic morphology, prone to be misdiagnosed as
other benign tumors. In the absence of dedifferentiation, the prognosis is generally better than
that of conventional osteosarcoma (3).
Parosteal Osteosarcoma onset is on average 10 years later than conventional
osteosarcoma. Age at onset is between 15 and 40 years, with a mean of 28 years. There seems
to be a female predominance, with a sex ratio of 1:3. POS usually presents with a globular,
juxta-articular mass that is fairly well limited, hard in consistency, slow-growing, generally
painless, but it can cause functional discomfort, limiting joint movement in one third of cases.
The painless quality of the disease explains the delay in diagnosis (1).
The tumor is usually located at the posterior aspect of the distal femur in about 70%
of cases, followed by the proximal tibia and proximal humerus. Rare locations, including
cranial, mandible, rib, clavicle, and tarsal bone, have also been reported (3). In our case
femoral parosteal osteosarcoma metastase to the lung is a rare,
Patients usually report a painless mass lasting for years, with decreased range of
movement of the adjacent joint. Dull pain and local tenderness are the second most common
symptoms. The protracted clinical behavior is an important feature distinguishing parosteal
osteosarcoma from other diseases of similar locations such as myositis ossificans and
high-gradesurface osteosarcoma, which usually have a more rapid onset (3). In reference with the
classic characteristics of the tumor, both masses were located at the postero-lateral portion of
the distal femur and appeared hard, immobile and tender with associated limitation of the
knee flexion onphysical examination (2).
Macroscopically, POS presents as a dense and well defined ossified mass attached to
the underlying cortex. On histologic grounds, the tumor mainly consists of hypocellular
fibrous stroma with minimal atypia of spindle cells and extensive osteoid in the form of well
demarcatedbony trabeculae, although smaller foci of cartilage are also encountered. A
cartilaginous component is observed in more than 50% of all POSs and in approximately
25% of cases this component lies at the periphery of the tumor. Pathologists and surgeons
must recognize this cartilaginous component so as not to confuse POS with osteochondroma
(2).
The radiology aspect is typical. PO presents as a radiopaque, metaphyseal mass
developing on the external side of the cortex, extending toward the soft tissues. This mass is
7 radiotransparent groove that separates the tumor from the bone cortex except at the base of
the implantation. When it is present, this sign has a high diagnostic value. It disappears in
voluminous tumors. According to Edeiken-Monroe et al., this clear ring corresponds to the
periosteum between the tumor and the bone cortex. Periosteal reaction, frequent in
conventional osteosarcoma, is absent in PO (1). A characteristic finding is a linear radiolucent
zone, separating the lesion from the host bone, except for the site of attachment, called the
cleavage plane which represents the uncalcified thickened periosteum. However, this
radiolucent cleft may be obliterated with advancing tumoral growth (2). In our case, involve
methaphyseal region with irregular pattern of mineralization and the periphery of the tumor
and less radiodense than the center.
CT scans define accurately the extent of the tumor and cortical integrity. MRI images
vary in relation to tumors size as well as the presence of dense osteoid, cartilage, hemorrhage,
necrosis or areas of high grade tumor or dedifferentiation. MRI is optimal for exhibiting the
appropriate biopsy site and potential medullary invasion prior intervention. Cortex continuity
with some peripheral erosions is a useful diagnosis key. Conversely, cortex and medullary
continuity are diagnostic features of osteochondroma. Perhaps the different appearances of
the medullary cavities of the lesions compared to the host bone should have raised suspicion
(2).
The differential diagnosis is made essentially with benign lesions such as osteoma,
osteochondroma, ossifying myositis, and periosteum desmoid. Clinical and radiological data
contribute enormously to the diagnosis. Histologically, these lesions do not develop in a
sarcomatous stroma and the cells are regular with no atypia or hyperchromatism. The
differential diagnosis is also made with low-grade periosteal osteosarcoma and
intramedullary osteosarcoma. The radiological presentation is different and there is no clear
space between the tumor and the cortex. From a macroscopic viewpoint, there is a
topographical difference between the tumor and the bone structures (1).
Chromosomal alterations in parosteal osteosarcomas are different from those in
conventional osteosarcomas. Parosteal osteosarcomas are characterized by one or more
supernumerary ring chromosomes, often as the sole alteration. CGH studies indicate gain at
12q13-15 as the minimal common region of amplification in the rings. The SAS, CDK4, and
MDM2 genes have been shown to be coamplified and overexpressed in a great proportion of
8 classical high grade osteosarcoma. Mutations in RB1 or microsatellite instability have not
been found to be present in parosteal osteosarcoma (4).
Surgery remains the treatment of choice. Wide excision with more than a 1cm
surgical margin is considered adequate, while incomplete excision almost inevitably leads to
local recurrence. In cases of marginal excision, a positive microscopic surgical margin
warrants a second operation. For recurrent disease, re-excision or amputation may provide a
possible cure in cases that lack tumor dedifferentiation. To achieve complete excision, a
preoperative diagnosis and radiological evaluation of the extent of disease are required. When
areas of dedifferentiation are suspected and proven by biopsy, neoadjuvant chemotherapy
may improve the clinical outcome (5). The prognosis of POS is good if the patient is properly
treated. Overall survival at 5 years is of the order of 91%. The risk of local recurrence
depends on the quality of the excision (1).
CONCLUSION
Parosteal Osteosarcoma is a rare case and is a low-grade malignant bone tumor characterized
by its insidious progress and good prognosis. It rarely leads to metastasis. Its treatment is
essentially surgical. The prognosis of POS is good if the patient is properly treated.
