Multicentric Primary Angiosarcoma of Bone Mimicking Metastasis on ¹⁸F-FDG PET/CT in a Patient with a History of Sigmoid Colon Cancer: a Case Report

Abstract

Primary angiosarcoma of the bone (PAB) is a rare and fatal high-grade malignant vascular bone tumor. We report a rare case of multicentric PAB mimicking bone metastasis in a 59-year-old female patient with a history of sigmoid colon cancer. This patient complained of lower back and pelvic pain and presented with multiple osteolytic bone lesions on plain radiography and pelvic computed tomography. First, bone metastasis of sigmoid colon cancer was suspected. However, on the ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) scan, the patient presented unusual multiple hypermetabolic osteolytic bone lesions involving contiguous bones of the lower half of the body. After bone biopsy, these lesions were confirmed to be multicentric PAB. To the best of our knowledge, this is the first case report of an ¹⁸F-FDG PET/CT scan in a patient with multicentric primary bone angiosarcoma.

Introduction

Angiosarcoma is rare and the most aggressive form of malignancy in the spectrum of vascular tumors [1]. Primary angiosarcoma of the bone (PAB) is an especially rare disease, and it accounts for less than 1 % of sarcomas. According to a previous study, about one-third of primary angiosarcomas are multicentric at diagnosis [2].

Here, we report the case of a multicentric PAB mimicking bone metastasis in a patient who had a history of sigmoid colon cancer. To the best of our knowledge, this is the first case report of an ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) scan in a patient with multicentric primary angiosarcoma of the bone. In this case, ¹⁸F-FDG PET/CT played a key role in the differential diagnosis.

Case Report

A 59-year-old female was referred to our hospital to evaluate the dull pain in her lower back and pelvic bones she had experienced for 2 months. She had a history of sigmoid colon cancer and had undergone laparoscopic anterior resection and adjuvant chemotherapy with doxyfluridine 9 years ago. The pathologic stage of the sigmoid colon cancer was confirmed as stage I without lymph node or distant metastasis. Her physical examination was unremarkable. The laboratory data were within normal ranges including carcinoembryonic antigen. On the plain radiography and computed tomography (CT) of the pelvis, multiple osteolytic lesions were detected in the lumbar spine and pelvic bones (Fig. 1a and c). The magnetic resonance (MR) image of the pelvis showed multiple lesions with gadolinium (Gd) enhancement (Fig. 1b) and low T1-weighted signal intensity (Fig. 1d) at the lumbar spine, both pelvic bones, and sacrum. These image findings suggested the possibility of bone metastasis based on her previous cancer history.

Fig. 1.

The initial imaging workup for pelvic pain. Plain radiography (a) and pelvic CT (c) show multiple osteolytic lesions in both pelvic bones and both proximal femori. Magnetic resonance (MR) images of the pelvis show multiple skeletal lesions with gadolinium enhancement (b) and low T1-weighted signal intensity (d). Bone scintigraphy shows lesions with mildly increased uptake in both pelvic bones, both femori and both tibiae (e)

Meanwhile, whole-body evaluation with bone scintigraphy showed abnormal mild uptake in the lower lumbar spine, both pelvic bones, and both femori and tibiae (Fig. 1e). The ¹⁸F-FDG PET/CT images also showed multiple osteolytic bone lesions with intense ¹⁸F-FDG uptake with a maximum standard uptake value of 13.1, contiguously involving the lower lumbar spine, both pelvic bones, and both femori without any other hypermetabolic lesions in the liver and lung (Fig. 2a). On the basis of (1) the localized pattern of osteolytic bone lesions in the lower half of the body, (2) the initial staging of sigmoid colon cancer, and (3) having no liver or lung metastasis after surgery, the possibility of another type of bone lesions than metastasis arose.

Fig. 2.

Maximum-intensity projection image of ¹⁸F-FDG PET shows multiple hypermetabolic bone lesions involving contiguous bones localized in the lower half of the body, without liver or lung metastasis (a). Transaxial images of PET (b), CT (c) and the fused image (d) show multiple hypermetabolic osteolytic lesions in the pelvic bones and sacrum

With the ultrasonography-guided bone biopsy of the left femur, angiosarcoma was pathologically diagnosed (Fig. 3b). Immunohistochemistry was positive for CD 31 (Fig. 3c) and weakly positive for CD 34 (Fig. 3d), which have been established as endothelial markers of vascular tumors [3]. The patient was subsequently diagnosed with multicentric primary angiosarcoma of the bone [4]. The patient underwent chemotherapy with doxorubicin for multicentric PAB instead of fluorourcil, leucovorin, irinotecan, and avastin, which had been initially planned for her palliative chemotherapy for multiple bone metastasis of sigmoid colon cancer. However, after undergoing one cycle of chemotherapy, she was re-admitted because of a pathologic femur neck fracture. During the emergency operation, right ventricular (RV) failure occurred, and she eventually expired despite the intensive care. Although the course of progression was too fast to evaluate the cause of RV failure, pulmonary fat embolism was suspected.

Fig. 3.

Histopathologic results of the patient. Adenocarcinoma of the sigmoid colon resected 9 years before the diagnosis of bone tumor (a) (×40, H&E). Histologic features of bone tumor. The tumor cells of left femur are arranged in solid or diffuse sheets with infiltrative growth pattern, replacing the marrow and encasing bony trabeculae (b) (×100, H&E). The tumor cells have abundant eosinophilic cytoplasm and large polygonal nuclei with frequent mitoses (23-25/10HPF), some of which show epithelioid appearance (inset; ×400, H&E). Immunohistochemical finding of bone tumor (c and d). The tumor cells are positive for CD31 (c) and weakly positive for CD34 (d), supporting the diagnosis of angiosarcoma (×200, IHC)

Discussion

Angiosarcoma is a very rare malignant endothelial vascular tumor, which can affect various sites but is commonly found in the soft tissue and skin [5]. PAB tends to develop in the long bones of the extremities, most frequently occuring in the femur, tibia, and humerus [6]. A third of PABs are multicentric at the time of diagnosis, and it is still not clear whether this is caused by metastatic spread or synchronous involvement of bones [2]. They often involve multiple bones in the same extremity, and the pattern of contiguous bone involvement of adjacent bones in PAB suggests a vascular origin of these tumors [7]. Pain is the most common symptom, and neurological deficit or other symptoms can occur depending on the size and location of the tumor.

Radiologic characteristics may be helpful in the diagnosis. Plain radiography and CT scans assess the characterization of the lesions and confirm their multiplicity. Most PAB lesions are osteolytic with variable marginations [8]. The degree of skeletal involvement of PAB is usually underestimated in bone scintigraphy because of its osteolytic nature [8]. In MR images, PAB lesions show Gd enhancement and nonspecifically decreased or variable signal intensity on T1-weighted images [8]. ¹⁸F-FDG uptake is usually high, similar to other high-grade soft tissue malignancies [9]. The final diagnosis is usually confirmed with pathologic findings through bone biopsy [4].

Multicentric PAB often can be confused with metastatic carcinoma. In our case, the patient had a history of sigmoid colon cancer. Although bone metastasis of colon cancer is uncommon, it could be a late manifestation of the disease. It is reported that about 17 % of colon cancer patients only show skeletal metastasis [10]. Metastastic bone lesions of colon cancer are predominantly osteolytic and occasionally osteosclerotic with Gd enhancement on MR images. However, the distribution of bone metastasis of colon cancer is usually in the vertebral column, especially the lumbar spine [10]. Our patient had multiple osteolytic lesions with Gd enhancement on MR images, which was suspected to be bone metastasis at first. However, the ¹⁸F-FDG PET/CT scan revealed the localized bone involvement of the lower half of the body, which is different from the typical skeletal metastasis pattern of colon cancer.

Both surgical resection and radiotherapy are recommended for the local control of PAB [11]. Radiation therapy followed by surgical resection should be considered for multicentric tumors [11]. Chemotherapy consisting of paclitaxel and doxorubicin has been performed with palliative intent. Generally, the prognosis of PAB is very poor. The 5-year survival is less than 30 % [11, 12]. However, according to previous reports, the multicentricity of PAB does not worsen the prognosis [13].

In summary, we report a case of multicentric primary angiosarcoma of the bone that mimicked bone metastasis in a patient with a history of sigmoid colon cancer. Multicentric primary angiosarcoma of the bone should be considered as one of the differential diagnoses for multiple hypermetabolic bone lesions, especially involving the long bones contiguously.