Clinical diagnosis
Case 215
【Progress】
She received EOB-MRI in university hospital which depicted FNH. She underwent sacral tumor resection in other university hospital whose pathologic specimen revealed chondrosarcoma of the sacrum.
【Discussion】
Liver tumor in this presentation has a typical imaging configuration of focal nodular hyperplasia. Namely, a hyper-vascular nodule without pseudo-capsule formation includes a center portion which is visualized as a hypo-vascular spot on an arterial phase and a gradual stain spot on a delayed phase, implying fibrous scar in the center (Figs 1, 2). Further, arterial branch comes from the center to the periphery such as a wheel-axis configuration. The nodule with hyper vascularity on an arterial phase does not render the nodule with a hypo-vascular lesion in a delayed phase but the nodule with an iso-density lesion. It is not contradictory in FNH (Fig. 1), while the nodule with hepatocellular carcinoma (HCC) becomes a nodule with low density in a delayed phase. That is because pseudo-capsule of HCC functions speedy washout of arterial blood. Then, it is not so difficult to diagnose FNH in our case.
Meanwhile, although CT delineated a sacral tumor in our case, it was very difficult to make an imaging diagnosis of chondrosarcoma. As sacral tumors, nonspecific tumors such as metastatic bone tumors, multiple myeloma and malignant lymphoma occur more often than specific sacral tumors (1-6). Sacral tumors are categorized into benign and malignant.
As benign sacral tumors, giant cell tumor, aneurysm bone cyst, osteoblastoma and osteoid osteoma are listed. Giant cell tumor arises from metaphysis and composes of histologically proliferation of osteoclasts, hemorrhage, and necrosis without calcification (4). Aneurysmal bone cyst also includes hemorrhage (5). Osteoid osteoma and osteoblastoma resembles together in points of clinical symptoms and histologic appearance (6). Osteoid osteoma is limited to the size less than 2cm. It contains non-ossification center with cortical margin. Osteoblastoma grows more than 1.5cm when it was found.
As malignant sacral tumors, chordoma and chondrosarcoma are listed (1-3). Chordoma arises from the remnant whose tissue is scheduled to differentiate to vertebral disk and spontaneously disappear at birth. The mutation of the remnant induces chordoma. Chordoma occurs most at skull base and sacrum. Chondrosarcoma arises from mutation of cartilage and arises from axis bone such as pelvis, vertebra and scapula but not from appendicular bone (3).
From a point of view of imaging interpretation, it is important to first, check hemorrhage, calc inside the sacral tumor. When hemorrhage is found, giant cell tumor and aneurysmal bone cyst should be listed for differential diagnosis. When calcification is found, chordoma, chondrosarcoma, chondroblastoma should be listed.
In our case, the sacral tumor contains calcification on CT. It implies that we should list chordoma, osteoblastoma and chondrosarcoma for differential diagnosis.
【Summary】
We presented a forty five-year-old female with liver focal nodular hyperplasia and sacrum chondrosarcoma. Abdomen and pelvic CT depicted a liver FNH with typical image pattern, whereas a sacral tumor which is hard to make exact diagnosis. The tumor contained calcification. It is borne in mind that nonspecific tumors such as metastatic bone tumors, multiple myeloma and malignant lymphoma occur more often than specific sacral tumors. When the sacral tumor contains hemorrhage, giant cell tumor and aneurysm bone cyst are listed for differentiation, while when it contains calcification, chordoma, chondrosarcoma, osteoblastoma and osteoid osteoma are listed for differentiation.
【References】
1.Llauger J et al. Primary Tumors of the Sacrum. American Journal of Roentgenology. 2000;174: 417-424.
2.Green R, et al. Pictorial review: imaging of primary osteosarcoma of the spine. Clin Radiol 1996; 51:325-329
3.Gelderblom, H et al. The clinical approach towards chondrosarcoma. The Oncologist. 2008;13: 320–329.
4.Brien EW, et al. Benign giant cell tumor of bone with osteosarcomatous transformation (“dedifferentiated” primary malignant GCT): report of two cases. Skeletal Radiol 1997; 26:246-255
5.Capanna R, et al. Aneurysmal bone cyst of the sacrum. Skeletal Radiol 1989; 18:109-113
6.Capanna R, et al. Sacral osteoid osteoma and osteoblastoma: a report of 13 cases. Arch Orthop Trauma Surg 1986; 105:205-210
2020.12.16