Introduction

Primary giant cell tumor of soft tissue (GCT-ST) is a low-grade malignant tumor originating from soft tissue. In view of histology, GCT-ST closely resembles the giant cell tumor of bone. GCT-ST has been classified as one of four entities for fibrous histiocytoma in the latest edition of the World Health Organization Classification of Soft Tissue Tumors [1]. This tumor often presents as a painless growing pattern, lacking characteristic clinical symptoms and signs. Most of them occur in the extremities and the superficial soft tissues of the trunk, while only a few takes place in the liver. Although GCT-ST is a relatively low malignant potential tumor in the view of histology, some patients who suffered from this tumor will die within weeks to months after surgery because of the aggressiveness [2]. Thus, early diagnosis is important, and preoperative imaging can supply the evidence of differential diagnosis to evaluate tumor malignancy. In this study, we report the findings of primary hepatic GCT with CT and MRI in this case, aiming to enhance the understanding of the imaging manifestations of this tumor.

Case presentation

A 56-year-old woman visited our medical center with the chief complaint of chills, fever, jaundice and anorexia for 3 days. The patient had an ultrasound examination in another hospital, which indicated a substantial intrahepatic tumor. In our hospital, CT showed a soft tissue tumor of the left lobe of liver with an eggshell-like peripheral hyperdense rim. The size of this lesion was 10.8 cm × 8.8 cm × 8.6 cm (anterior-posterior × left-right × superior-inferior). The internal component density was about 25–30 Hounsfield units (HU). The boundary of the lesion was unclear. Multiple stones could be seen in the lower section of the common bile duct and the distal bile ducts were diffusely dilated. Furthermore, the left portal vein was not clearly displayed, as shown in Fig. 1. MRI was conducted to further assess the tumor. The lesion showed iso-intense with peripheral hypo-intense on T1WI (Fig. 2a and b) and mainly inhomogeneous hypo-intense on fat-suppressed T2WI (Fig. 2c and d). It was mainly hypointense and peripheral linear hyperintense on DWI images with a b-value of 800 (Fig. 2e) and hyperintense on apparent diffusion coefficient (ADC) (Fig. 2f). In this study, the mean ADC value of hepatic GCT lesions was 1.0 × 10⁻³ mm² s⁻¹ (Fig. 2i). In addition, the persistent nodular and patchy enhancement in post-contrast T1WI (Fig. 2g and h) also can be found.

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Abdominal computed tomography. Axial CT showed a soft tissue tumor of the left lobe of liver with eggshell-like peripheral hyperdense rim (the white arrow)

Citation: Imaging 15, 1; 10.1556/1647.2023.00107

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Abdominal magnetic resonance image. A large nodular lesion was observed in the left lobe of liver. The size of this lesion was 10.8 cm × 8.8 cm × 8.6 cm (anterior-posterior × left-right × superior-inferior). The lesion showed iso-intense with peripheral hypo-intense on T1WI (a and b), and mainly inhomogeneous hypo-intense on fat-suppressed T2WI (c and d). Moreover, it was mainly hypointense and peripheral linear hyperintense on DWI (e) images with a b-value of 800 (b800) and iso-hyperintense on ADC (f). The mean ADC value of hepatic GCT lesions was 1.0 × 10⁻³ mm²/s (i). In addition, the persistent nodular and patchy enhancement in post-contrast T1WI (g) also can be found. The lesions were hyperintense on DWI and hypointense on ADC. While the post-contrast T1WI showed a circular enhancement around the lesion. Coronal T1 MR postcontrast (h).

Citation: Imaging 15, 1; 10.1556/1647.2023.00107

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After that, combined with the postoperative pathological, immunohistochemical analysis and whole-body bone scintigraphy, it was found that this disease was highly possible to be a hepatic GCT. Based on the consult of the patient, there is no history of giant cell tumor in bone or other soft tissue. Consequently, this disease was finally diagnosed as a primary hepatic GCT with intermediate malignancy, according to the WHO criteria.

Discussion

GCT-ST was first described by Salm and Sissons in 1972 [3]. It is characterized by the fact that the tumor occurs in soft tissue, which is clinically and histologically like the giant cell tumor of bone. Compared with skeletal GCT, GCT-ST has unpredictable behavior which becomes aggressive [4]. Besides, the GCT-ST occurring in the liver is extremely rare, only 9 cases have been reported up to now [5], and we are the 10th case.

Previous studies have suggested that CT images of GCT-ST usually show a low-density tumor. MRI images mostly showed low-isointense on T1WI and hyperintense on T2WI [6], which are intensely heterogeneous enhancements on post-contrast T1WI. Internal areas without enhancement are often found due to necrosis, cystic degeneration and fibrous tissue [7]. In this study, the imaging findings of the tumors were partially consistent with those reported in previous studies. The characteristic CT findings of this case were multiple ring-like calcifications at the edge of the tumor. MRI showed a low-intense ring around the tumor on T1WI, T2WI, DWI and ADC, which showed no enhancement on post-contrast T1-weighted images. In addition, the range of the annular hypointense zone on MRI is larger than the range of calcification on CT, considering that part of the ring hypointense zone may be a fibrous component.

There are several indications for MRI in this case. Firstly, as MRI has a relatively high spatial resolution, the implementation of dynamic enhancement scans can further detect multiple micro lesions in the liver and show the tumor hemodynamics as well as the peripheral vascular invasion. Secondly, MRI examination has unique merits in presenting the content of fibrous and cellular components within the lesion, while this case of hepatic GST is mainly featured by the higher fibrous constituents. Thirdly, DWI techniques are well-established in liver lesions and can be used for benign and malignant identification. Typically, if the ADC value is higher than the threshold of 1.0 × 10⁻³ mm² s⁻¹, the mass is considered to be benign [7]. In this study, the mean ADC value of hepatic GCT lesions was 1.0 × 10⁻³ mm² s⁻¹. The ADC values of the hepatic GCT were consistent with tumor pathology as intermediate or low-grade malignancy. Several guidelines have endorsed Contrast-enhanced ultrasonography (CEUS) for the detection of focal liver lesions with high diagnostic accuracy. CEUS has the advantage of imaging enhancement in real time with high spatial resolution, and it allows the assessment of characteristic enhancement patterns of focal liver lesions in all vascular phases. Furthermore, CEUS also makes a unique contribution to the already established protocols for diagnosing focal liver lesions using CT and MR imaging [8].

Differential diagnoses of primary hepatic GCT include intrahepatic cholangiocarcinoma (ICC), hepatocellular carcinoma (HCC) and metastases of liver (ML). The typical features of the three types of tumors can be concluded as follows. I). ICC has peripheral arterial enhancement and peripheral washout on portal venous or delayed images due to increased peripheral cellularity on both CT and MRI with extracellular after contrast. Central hyperenhancement on delayed imaging is commonly seen and related to the fibrous stroma. Additional MR imaging features are T1 hypointensity and peripheral T2 hyperintensity. Hepatic capsular retraction, daughter/satellite nodules, or intratumoral artery signs can also be used to help to differentiate ICC and hepatic GCT [9]. Moreover, ICC does not contain calcified components. II). The typical enhancement pattern of HCC on contrast-enhanced CT or MRI is characterized by hyper-enhancement in the arterial phase and wash out during the portal venous and late phases. This has around 60% sensitivity and 96–100% specificity [10]. Hepatic GCT has persistent delayed enhancement rather than wash out, which can be used as a differentiating feature. In addition, pseudocapsule is another characteristic of HCC. The increased clinical biochemical Alpha-FetoProtein (AFP) is also of high diagnostic value for HCC. Generally, HCC does not contain calcified and fiber components, which can also be used to make distinguish between HCC and hepatic GCT. III). Liver Metastases usually appeared as multiple and wide distributions. The imaging findings of liver metastases largely hinge on multifarious primary tumor-specific factors. Characteristic imaging features are composed of the target sign on T2-weighted images, the peripheral rim washout sign, the peritumor hyperintensity during the hepatobiliary phase, hypervascular metastasis, calcification, the marked hyperintensity on T1-weighted images, hepatic capsular retraction, the vessel-penetrating sign, distribution of liver metastases and rare intraductal forms of metastases. In this study, the patient had no history of primary tumors and radiographic findings were inconsistent.

Conclusions

In conclusion, our case illustrated CT and MRI features of primary GCT-ST located in the liver. Pre-operative diagnosis of hepatic GCT is challenging. It plays a very important role in obtaining comprehensive information about the tumor to achieve the diagnosis. Therefore, the diagnosis of hepatic GCT should be considered when the tumor is characterized by fibrous components with calcification and persistent heterogeneous enhancement.

Author's contribution

Lei He collected and analyzed the data and drafted the manuscript. Yalin Zhang contributed to the analysis of the content and the final approval of the version to be published. All authors read and approved the final manuscript.

Ethical Statement

The study submitted to IMAGING have been conducted in accordance with the Declaration of Helsinki and according to requirements of all applicable local and international standards.

Funding sources

This work received no external funding.

Conflict of interest

The authors declare that they have no competing interests.