Undifferentiated embryonal sarcoma of liver arising within mesenchymal hamartoma in a child "case report"

Abstract

Background

Primary pediatric liver tumors are scarce. Undifferentiated embryonal sarcoma of the liver (UESL) embraces nine to fifteen percent of the pediatric hepatic neoplasms. Mesenchymal hamartoma of the liver (MHL) is the second most prevalent benign pediatric hepatic neoplasm following infantile hemangioendothelioma.

Case presentation

A 6-year-old female child presented with vague diffuse abdominal pain and palpable right lumbar mass by clinical examination. The US showed a well-circumscribed large right hepatic complex multilocular cystic lesion with multiple internal septations and some turbid loculi. The constellation of CT and dynamic MRI findings raised the presence of atypical suspicious complex cystic hepatic mass lesion with hemorrhagic, calcific entities and internal soft tissue enhancement. The histopathological correlation proved UESL on the background of MHL.

Conclusions

A case of a pediatric hepatic complex cystic lesion, which had typical ultrasound features of MHL, however, CT and MRI had atypical suspicious criteria. Finally, our case is presented as UESL in the background of MHL based upon pathological diagnosis. The radiologists must be familiar with overlapped entities between MHL, UESL, and other differential diagnosis entities regarding pediatric hepatic neoplasms.

Background

Primary pediatric liver tumors are scarce and account for less than two percent of whole pediatric tumors. Hepatoblastoma and hepatocellular carcinoma are considered the most common hepatic neoplasms in children age group. Undifferentiated embryonal sarcoma of the liver (UESL) embraces nine to fifteen percent of the residual pediatric hepatic neoplasms, the frequency of UESL stays stunted with 0.6 to 1.2 patients per one million people. Ninety percent of UESL patients are between 6 and 10 years of age. The sparseness of this neoplasm results in the scarcity of research that endorses the unique imaging characteristics. So, UESL is frequently misinterpreted as other entities of liver malignancies [1].

The postoperative cytology and immunostaining analysis are the final actual diagnosis of UESL. As one of the high malignancies, UESL usually sends distant pleural pulmonary, and peritoneal metastasis, evolving in a miserable scenario. Formerly, management for UESL chiefly embraces hepatectomy with postoperative radio-chemotherapy [2]. The second prevalent benign pediatric liver neoplasm is a mesenchymal hamartoma of the liver (MHL) followed by infantile hemangioendothelioma [3]. The majority of MH cases elicit cystic lesions. MHL is frequently spotted in children younger than 2 years old, with the approximate majority of lesions (95%) by age 5 years. The frequent clinical symptom is painless abdominal distention. No unique laboratory parameter and serum AFP titers are classically unremarkable [4].

The aim of this case report is to highlight the possibility of the development of UESL on top of MHL.

Case presentation

A 6-year-old girl presented with vague diffuse abdominal pain. Physical assessment by the pediatric surgeon revealed a palpable right lumbar mass. The patient was directed to our medical imaging department for abdominal ultrasonography (US).

The US showed a well-defined large right hepatic complex multilocular cystic lesion with multiple internal septations and some turbid loculi. Also, peripheral coarse calcifications were noted with hypovascular septa by Doppler evaluation (Fig. 1).

Fig. 1

The abdominal US showed a well-defined right hepatic multilocular cystic mass (A) with turbid locules (black star) (B), Peripheral coarse calcification (white arrow) (C), and scanty septal vascularity by Doppler (red arrow) (D)

Abdominopelvic contrast-enhanced CT (Fig. 2) revealed a well-defined predominant hypodense lesion within the right hepatic lobe (segments VII and VIII). It measured about 9 × 8 × 10 cm in three dimensions. Faint peripheral septal enhancement without avid solid enhanced component noted. Anterior marginal coarse calcification traced. As a better characterization of this lesion is required, further MRI is recommended. MRI showed the lesion was significant hyperintense on the T2WI and hypointense on the T1WI, with numerous thickened trabecular patterns and internal areas of hemorrhagic high T1 signal intensity. Dynamic post-contrast (Gadoterate Meglumine) images showed enhanced internal septations (Fig. 3).

Fig. 2

Axial non-contrast CT shows a large hypodense complex cystic right hepatic lesion at segment VII with peripheral coarse calcification (arrow) (A). B Post-contrast CT (Porto venous phase) revealed faint septal enhancement without significant solid enhanced masses

Fig. 3

A Axial T2WI MRI, B T1WI shows internal areas of high signal in T1 and corresponding shading signal in T2 denoting hemorrhagic element. C, D ADC and DWI with b value 800 show no restriction diffusion. E Axial T1WI arterial post-contrast shows enhanced internal septations

Regarding own our case, the ultrasound features were unique to MHL (nontypical for UESL), however the presence of calcification and turbid locules were raising the possibility of an underlying complicated entity. CT and dynamic MRI supported our suspicion of the presence of suspicious complex cystic hepatic mass lesion with hemorrhagic and calcific entities.

Based on all our imaging findings; the referred surgeon decided to do directly total right hepatectomy and histopathological correlation instead of radiological guided biopsy.

The pathology report described a large subcapsular mass with focal rupture of the liver capsule over the mass. The cut surface was soft and oedematous with multiple small cysts as the gross picture (Fig. 4). The microscopic picture revealed dilated bile ducts surrounded by mildly to moderately cellular oedematous to the myxoid stroma. The stroma showed proliferation of atypical spindle cells displayed large hyperchromatic nuclei with scattered bizarre multinucleated cells. The atypical stromal cells show positive staining by immune histo chemistry (Fig. 5). In the end, it stated that UESL was in the background of MHL.

Fig. 4

A right hepatectomy specimen photograph elicited a well-defined, heterogeneous, principally subcapsular solid growth, with hemorrhagic foci and frequent minor cystic portions. The residue of the normal hepatic tissue was noted

Fig. 5

A–D Hematoxylin and eosin staining reveals undifferentiated sarcoma of multinucleated and hyperchromatic cells embedded in a dense pleomorphic stroma. Immunohistochemistry shows bizarre cells with hyperchromatic tumor cells

Discussion

The classic sonographic criteria of mesenchymal hamartoma were the cystic pattern that exhibited anechoic or predominant anechoic with variable thickness echogenic septa. Low-level echo fluid loculations may be noticed. Color Doppler imaging displays fairly tiny blood flow, which is restricted to septa [3].

At CT, MHL shows as a complex cystic mass. The cystic portion displays fluid density, while the stromal portion is hypodense to the adjacent hepatic parenchyma. Post-contrast studies, the septa, and solid portion enhancement were noted. Hemorrhage is not a frequent feature in mesenchymal hamartoma [5].

At MR imaging, the solid component may show low signal intensity to surrounding hepatic parenchyma on either T1 or T2WIs due to fibrosis. The cystic component is usually near fluid signal intensity on T2WIs. After dynamic sequences, mild enhancement is restricted to the septa and solid portions [4].

MHL is arranged of a mucous matrix and a large number of star and fusiform primary mesenchymal cells though the tumor cells themselves do not display heteromorphism [6].

UESL stakes several imaging and pathologic criteria with MHL, however, is picked in an elder age category (6 to 10 years old). At histopathologic assessment, UESL is recognized by the prevalent realization of hemorrhage and necrosis among malignant backgrounds [7].

A sole imaging distinctive criteria of UESL is a principally solid echo pattern in the US however cystic pattern at CT and MR imaging due to the high-water content of the abundant myxoid contents. CT shows chiefly fluid density (88% of tumor size) with soft tissue foci, generally at the margins and intervening different septal breadth. Central hyperdense foci signifying recent hemorrhage may also be existing. Calcifications are unusual [7, 8]. After contrast administration, mainly marginal enhancement is distinguished on delayed series. At MR imaging, UESL is mainly of fluid signal intensity on T1 and T2WI. Focal portions of high signal intensity T1 and relatively low signal intensity in T2WIs are often seen, which match with bleeding in the gross sectional anatomy. These hemorrhagic foci are superiorly realized with MR imaging than with CT [8, 9]. After dynamic sequences, heterogeneous enhancement of the peripheral and solid components of the lesion is detected. MR imaging added more information for the characterization of resectability and assessment of vascular pedicles, the biliary system, and locoregional lymph nodes [10].

Follow-up mesenchymal hamartoma is not favored due to the less incidence of progressive course, in addition to the scare recordings of malignant conversion to UESL. The long-term survival rate is great (90%), although inadequate resection was done [7].

The chief differential diagnostic issue is MHL, which is pathologically and radiologically analogous to UESL. The patient age category may support one diagnosis more than the other, as UESL is sporadic below the age of 5 years while MHL is mostly identified by the age of 2 years; though, histopathological correlation is essential to create a conclusive analysis [3, 7].

Of eleven patients spotted in analogous research, five cases of UESL (45%) evolved in the background of MHL with distinguishable transitional zones. Some proof recommends that pre-existing MHL may progress to malignant degeneration and advance into UESL. This variety of malignant conversion of hamartomatous entities is not a scarce outcome. It established a histologic association between UES and MH. The connection in immunohistochemical staining and clinical performances affords supplementary clues that MHL and UESL may be an evolving spectrum of the same disease, and reflect that some trigger or genetic predilection may be the core for the malignant transformation of benign MHL [11].

Also, another study stated that the pathologic evaluation of its case reveals MHL of the liver in association with several malignant sarcomatous elements, which advances the likelihood of it being a precursor lesion for UESL [12].

Our current case matched with the previously mentioned research studies.

However, still, the available radiological research studies that discuss the presence of UESL in the background of MHL scarcely. Complete resection stays the management backbone, but the involvement of multimodal treatment has shown a significant impact on the outcome, and this entity is currently assumed treatable. The utilization of neoadjuvant chemotherapy affords the majority of these neoplasms responsive to successful surgical excision [7, 8 ].

Our case was referred to a special pediatric cancer hospital to receive non-rhabdomyosarcoma protocol and follow-up by different imaging modalities showed no residual or recurrent tumors.

Conclusions

A case of a pediatric hepatic complex cystic lesion, which had typical ultrasound features of MHL, however, CT and MRI had atypical suspicious criteria. Finally, our case is presented as UESL in the background of MHL. The radiologists must be familiar with overlapped entities between MHL, UESL, and other differential diagnosis entities regarding pediatric hepatic neoplasms.