Keywords
Bone scan - osteosarcoma - pleural metastases
Introduction
Osteosarcoma (OS), the most common primary malignant neoplasm of the bone, has the
second-highest mortality rate among pediatric cancers, and is most commonly diagnosed
in patients in the second and third decades of life.[1] It is a fast-growing tumor, with a high risk of local recurrence and distant metastases,
with the lung and bone being the most common sites of dissemination, occurring in
approximately 80% of cases,[2] but metastases to other sites are uncommon and occur in fewer than 10% of cases.[3]
Bone scan scintigraphy (BS) with 99m technetium methylene diphosphonate (99mTc-MDP) is useful for the detection of distant bone disease, which is the second most
likely location for metastatic spread. Positive findings on the bone scan may warrant
additional imaging of the area of concern and ultimately, a biopsy may be necessary
to prove the definitive presence of distant bone disease.[4]
Pleural metastases rarely occurs and the appearance of diffuse pleural thickening
with ossification is not usual, with few such cases reported currently reported due
to the state-of-art treatment protocols.[5],[6] Most of the reported cases occurred after the initial treatment and isolated pleural
metastases without lung metastases are unusual.[7]
Histologically, this tumor is composed of a sarcomatous fibroblastic stroma in which
osteoblastic activity induces the formation of tumor osteoid and bone. Uptake of bone-seeking
radionuclides in OS metastases have been described and the mechanism of uptake is
believed to be direct incorporation in the osteoid deposited by the tumor, including
pleural metastases.[8]
Herein, we report an interesting case of OS with bilateral pleural and lung metastases,
without bone involvement detected by BS.
Case Report
A 29-year-old woman was diagnosed with high-grade fibroblastic OS in the proximal
left tibia. She was initially treated with chemotherapy, followed by amputation of
the left lower limb. Thirteen months later, she complained of dyspnea and chest pain.
A computed tomography (CT) scan of the chest was performed and showed multiple pulmonary
and pleural nodules suggestive of involvement secondary to the OS. In addition, a
planar and single-photon emission computed tomography/CT, BS with 99mTc-MDP was also requested and demonstrated bilateral diffuse pleural plaques, which
corresponded to multiple calcified foci of thickening and nodules [Figure 1] and [Figure 2]. BS did not show signs of bone metastases.
Figure 1 Planar images of the bone scan showing diffuse areas of 99mtechnetium methylene diphosphonate uptake in the pleura projection bilaterally
Figure 2 Coronal computed tomography image showing multiple calcified foci of thickening and
nodules in both pleura (left) and the single-photon emission computed tomography/computed
tomography fusion showing the 99mtechnetium methylene diphosphonate uptake correspondence in these areas (right)
After restaging examinations, systemic palliative treatment for the patient was started.
Discussion
OS is an aggressive primary bone tumor arising from primitive bone-forming cells.[6] The metastases of OS are typically hematogenous and the most common sites are lungs
and bone.[2] Pleural metastases of OS are exceedingly rare[6] and the appearance of diffuse pleural thickening with ossification is also unusual,
and few such cases have been reported.[3] A study that included 134 patients diagnosed with OS showed that 13 of them had
extrapulmonary metastases, and only two of them presented pleural metastases.[3]
Pleural metastases in OS can occur by two mechanisms: Direct contact of pleura with
the lung metastases and hematogenous spread of OS.[7]
Conventional imaging features of extraskeletal OSs are largely nonspecific.[9] It is a fact that this kind of tumor can produce bone and osteoid,[10] BS can help to show these lesions, including pleural metastases.
BS is often used in conjunction with CT to identify metastases, and the presence or
absence of metastatic disease remains one of the most important predictors of patient
outcome.[4]
Although CT had already shown lung and pleural lesions, our intention was to demonstrate
a rare presentation of OS and an unusual image of pleural metastases detected by BS,
and its diffuse pattern of distribution compared to the anatomical diagnostic method.
Declaration of patient consent
The authors certify that they have obtained all appropriate patient consent forms.
In the form the patient(s) has/have given his/her/their consent for his/her/their
images and other clinical information to be reported in the journal. The patients
understand that their names and initials will not be published and due efforts will
be made to conceal their identity, but anonymity cannot bechrological order guaranteed.
