HCS is an extremely rare malignant tumor due to its composition of mixed carcinomatous and sarcomatous elements. Specifically, the WHO defines HCS as a malignant tumor containing a heterogeneous mixture of carcinomatous, either hepatocellular carcinoma (HCC) or cholangiolocellular carcinoma (CCC), and sarcomatous elements [1]. In addition, this tumor is challenging to diagnose clinically; it is also aggressive and has a poor prognosis, which may be associated with a high frequency of early metastasis and advanced stage at diagnosis.
Based on previously published cases in the literature, we summarized the clinical and imaging manifestations of this rare disease. HCS is more common in elderly male patients, especially those with a history of CHB [2]. This shows that the occurrence of HCS may be related to hepatitis B virus (HBV) infection as well as cirrhosis or fibrosis history, although Fengli Bin and others hold different opinions [3]. Moreover, in most cases, the tumor appears to always be exceedingly bulky, with an average diameter of approximately 12.5 cm (range, 3.2 to 25 cm) [4]. However, symptoms related to the tumor are usually nonspecific, including right upper abdominal pain, jaundice, and loss of appetite as the most common complaints. Only a small minority of HCS cases can be detected based on elevation of serum tumor markers, such as alpha-fetoprotein (AFP), carcinoembryonic antigen (CEA), or carbohydrate antigen 19 − 9 (CA19-9). As a result, the possibility of HCS cannot be ruled out by results within the normal range. The present and previous reports have found that CT is the most common imaging method for HCS [5]. In the present study, most HCS lesions presented extensive necrotic changes. This phenomenon may be related to the sarcomatous elements of HCS growing so rapidly that the blood supply cannot provide adequate nutritional support for the tumor, which may lead to necrosis [6]. Consequently, HCS always presents on CT scans as heterogeneous, low-attenuation lesions with large necrotic cystic portions. Compared to HCC, HCS rarely exhibits a capsule, which may contribute to the poor prognosis of HCC. In previous reports, only 6 tumors with diameters < 5.0 cm were reported to exhibit capsules [7, 8]. The absence of a capsule in most HCS tumors might be due to their highly aggressive behavior [4]. It is a pathological feature critical for the final diagnosis.
As mentioned above, histologically, HCS tumors consist of carcinomatous and sarcomatous elements. The carcinomatous components are mainly made up of HCC, which is the most common malignant tumor of the liver, CCC, or a combination of both. In contrast, sarcomatous elements show various levels of differentiation, including leiomyosarcoma, rhabdomyosarcoma, fibrosarcoma, chondrosarcoma, osteosarcoma, undifferentiated spindle cells, and malignant fibrous histiocytoma. Therefore, carcinosarcoma not only has the characteristics of carcinomas but also the manifestations of sarcoma. However, the pathogenesis of this rare tumor remains unclear. Increasing evidence in recent years supports the theory that carcinosarcoma is monoclonal in origin [9]. Thompson et al. also proved that HCS tumors develop from a multipotent hepatic stem or progenitor cell, which then differentiates into both carcinomatous and sarcomatous neoplasms [10].
The prognosis of HCS cases is often worse than that of conventional liver neoplasms, which may be attributed to the aggressive sarcomatous elements with their extensive differentiation [11]. A study from Japan analyzed 21 reported cases of primary HCS and found that the survival time of patients who received surgery and postoperative comprehensive treatment was significantly longer than that of patients who did not undergo surgery, with a survival time for the former group of up to 30 months [12, 13]. Surgical resection appears to be the most effective treatment for HCS. Although radical resection is still recommended, the presence of extrahepatic metastases, vessel involvement, and invasion of surrounding organs may render curative resection impossible [4, 14]. In our case, the patient who underwent an open surgery with partial hepatectomy and intraperitoneal perfusion chemotherapy had a relapse only 5 months after the operation. Meanwhile, Daisuke Kurita et al. reported that a 67-year-old Japanese man underwent chemoradiotherapy with doxorubicin and ifosfamide for unresectable lymph node recurrence after right hepatectomy. Surprisingly, chemoradiotherapy significantly decreased the size of the lymph node recurrence and delivered a progression-free survival of 12 months, indicating that doxorubicin and ifosfamide chemoradiotherapy for metastatic HCS may prolong survival in patients with unresectable lesions [2, 15]. As a result, it is believed that chemotherapy for HCS will become increasingly significant in clinical practice and that surgery combined with chemotherapy will be the mainstream treatment for HCS. In addition, the clinical diagnosis of HCS will also benefit from identification of imaging features, such as cystic alterations, necrosis, and the absence of tumor capsules, even though pathological testing remains the gold standard for diagnosing liver cancer.
In summary, we present a highly unusual case of primary hepatic carcinosarcoma with spontaneous rupture as the initial symptom, along with extensive follow-up information, imaging, and pathology findings. Invariably, early diagnosis is crucial for the successful treatment of malignant tumors. HCS should be considered when the following imaging findings are present: cystic changes, necrosis, and the lack of tumor capsules. Currently, radical resection remains the best available treatment for HCS if the presence of vessel involvement, extrahepatic metastases, and invasion of surrounding organs has not occurred. However, surgical resection combined with chemotherapy may be the mainstream treatment for HCS in the future. Overall, our understanding of this disease remains only at the tip of the iceberg, and additional case reports are required to further characterize this rare tumor.