【One case per day】Chinese Journal of Radiology: A case of invasive osteoblastoma of the shoulder blade complicated with aneurysm-like bone cyst

X-ray shows round, uneven high-density opacities (arrows) of the left shoulder blade, surrounded by linear density reduction on the inner side of its upper edge Fig.
2 The CT axis shows the osteogenic part (arrow) and soft tissue shadow (arrow) in the mass Fig.
3 CT coronal reorganization image shows the overall situation of the mass, cortical destruction and defect of the shoulder glenoid and the lower edge of the scapula Fig.
4 MR T2WI shows low-signal shadows and multiple liquid planes (arrows) in the mass Fig.
5 pathological films show a large number of epithelial-like cells around the new bone tissue, with large cell volume and rich cytoplasm, Nucleoli evident (HE ×200)

The patient, a 47-year-old male, sought medical treatment
for 3 months with limited shoulder movement and a mass found for 1 year, mainly due to left shoulder pain for 10 years.
Physical examination: a 3 cm× 4 cm×5 cm mass palpable under the left scapula, tender, tough, and well-defined
edges.
X-ray: a bone lesion area can be seen on the left shoulder blade, which is uneven and high-density opacity, and the inner upper edge can be surrounded by linear low-density opacities, and the scapula and the lower edge of the shoulder blade are incomplete (Figure 1).

CT: Left scapular round uneven bony high-density opacity, 4 cm×5 cm×8 cm, high-density shadow surrounded by soft tissue density opacity, high-density opacities in and around the dense tissue shadow, corical destruction of the scapular joint surface and the lower edge of the scapula, and clear lesion edges (Fig.
2, 3).

MR image: left shoulder blade mass, the central part of T1WI mass is a low-signal or non-signaling area, corresponding to the CT image osteogenesis area, slightly higher and high-signal shadows can be seen in the low-signal or non-signaling area and edges, fluid level is visible, and the lesion edge is clear (Figure 4).

Postoperative pathology: A large number of epithelioid cells around the neonatal bone tissue were shown under the microscope, with large cell volume, rich cytoplasm, and obvious nucleolus (Figure 5).

Diagnosis of invasive osteoblastoma with aneurysm-like bone cyst
.

discuss

Osteoblastoma is a rare primary bone tumor, and invasive osteoblastoma is less common than ordinary osteoblastoma, and the author has not seen information on
its incidence.
Histopathologically aggressive osteoblastoma is a large area of osteoblasts, which are 2 times the size of ordinary osteoblasts, the cells are full, round, cytoplasmic eosinophilic, and the nucleoli are obvious, such cells are called epithelioid osteoblasts
.
The most common sites of this tumor include the spine, femur, skull, hand and foot bones, humerus, tibia, and fibula, and in this case the shoulder blades, which are rare sites
.
Invasive osteoblastoma is painful, and muscle wasting
is often present in the affected area.

The imaging features of invasive osteoblastoma are as follows: x-rays show that the diameter of the invasive osteoblastoma lesion is larger than that of the typical osteoblastoma, the lesion is osteolytic destruction, the lesion boundary is clear, different degrees of osteosclerosis can be seen in the lesion, and occasionally periosteal reactions and soft tissue masses
.
CT may show lesion bone destruction, small blossoms, and soft-tissue masses
.
Aggressive osteoblastoma MR tumors T2WI exhibit low or intermediate signal intensity, T1WI intermediate high signal intensity
.
Aggressive osteoblastomas may be associated with secondary aneurysm-like bone cysts
.

According to X-ray and CT manifestations before surgery, the lower edge and scapuloid cortex are destroyed, in which large osteogenesis has the characteristics of typical osteoblastoma, but due to the large soft tissue components, the osteogenic part is incomplete compared with the typical osteoblastoma, so it is diagnosed as a malignant osteogenic tumor, and osteoblastoma or aggressive osteoblastoma
is not considered.
MR images are consistent with aneurysm-like bone cyst-like changes, pathologically confirmed as secondary aneurysm-like bone
cysts.

Aggressive osteoblastoma is closer to the characteristics of malignant osteogenic tumors on X-ray and CT, but the osteogenic morphology and type within it are similar to typical osteoblastomas, and MR images can clearly show the soft tissue part of the lesion, especially showing that secondary aneurysm-like bone cyst changes are of great significance
.