Author Affiliations: Departments of Histopathology (Silvanto A and Bagwan IN) and General Sugery (Karanjia ND), Royal Surrey County Hospital, Guildford, UK

Corresponding Author: Izhar N Bagwan, MD, Department of Histopathology, Royal Surrey County Hospital, Egerton Road, Guildford GU2 7XX, UK (Email: izhar.bagwan@nhs.net)

 

© 2015, Hepatobiliary Pancreat Dis Int. All rights reserved.

doi: 10.1016/S1499-3872(15)60365-4

Published online May 15, 2015.

 

 

Contributors: BIN proposed the study. KND performed the operation, and SA performed research and wrote the first draft. All authors contributed to the design and interpretation of the study and to further drafts. BIN is the guarantor.

Funding: None.

Ethical approval: Not needed.

Competing interest: No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article.

 

 

ABSTRACT: Extrapleural solitary fibrous tumor (SFT) is an uncommon mesenchymal neoplasm, presenting most commonly in the intrathoracic sites but which has been reported at numerous extrathoracic locations. The majority of intra-thoracic SFTs are benign, but 10%-15% behave aggressively. We report a case of primary hepatic SFT with histologically benign and malignant areas. A 65-year-old man underwent an abdominal CT scan following a cerebrovascular accident, which demonstrated a sharply demarcated large liver mass with a heterogenous enhancing area and occupying most of the left lobe of the liver. Histological examination following a hemihepatectomy showed an SFT with morphological patterns ranging from benign to malignant areas, including pleomorphism, increased cellularity, herringbone pattern, necrosis and a raised mitotic count. On review of the literature, only an occasional case report with malignant areas in a hepatic SFT was identified. This case highlights that SFT should be included in the differential diagnosis of a hepatic spindle cell lesion, and that on rare occasions, malignant areas can occur in this already uncommon neoplasm.

 

(Hepatobiliary Pancreat Dis Int 2015;14:665-668)

KEY WORDS: liver tumors; malignant (non-HCC); liver surgery; pathological changes

 

Solitary fibrous tumor (SFT) is an uncommon mesenchymal spindle cell neoplasm, described initially as a pleural based lesion, but which has since been described in numerous extrathoracic sites^[1] and its clinical presentation is variable according to the site of origin. SFTs have a characteristics histological appearance, being described as having a 'patternless' pattern composed of bland spindle cells. They have alternating hyper- and hypocellular areas, keloid-like hyalinised collagen and a 'hemangiopericytoma-like' prominent branching vasculature.^[1] Cytological atypia is not normally a feature and mitotic activity is generally absent to near-absent. Immunohistochemically, SFTs express BCL-2, CD34 and CD99. Approximately 10%-15% of intrathoracic SFTs show malignant features histologically and/or in terms of clinical behavior, but such cases are rare at other sites including the liver.^[1] We report a case of primary SFT of the liver with histologically benign and malignant areas.

 

 

A 65-year-old man was admitted to our hospital following a right-sided cerebrovascular accident. Laboratory investigations revealed mild anemia (hemoglobulin 105 g/L) and slightly abnormal liver function tests (raised alanine aminotransferase and aspartate aminotransferase). A CT scan of the chest, abdomen and pelvis identified an incidental sharply demarcated large liver mass with a heterogenous enhancing area and occupying most of the left lobe of the liver, suspected to be a hepatocellular carcinoma. Focal cystic areas were identified on CT scan. There was no evidence of metastasis on the CT or a subsequent PET scan. Having recovered from his stroke, the patient underwent a left hemihepatectomy from which he recovered uneventfully.

 

Macroscopically, the left lobe of the liver contained a multinodular mass measuring 180 mm in maximum diameter (Fig. 1A). This had a solid and cystic cut surface, with a whorled appearance in places (Fig. 1B). Necrosis was also identifiable macroscopically. The lesion was present 1-2 mm from the liver resection margin.

 

Histological examination showed liver parenchyma containing an encapsulated spindle cell tumor with areas of variable cellularity, involving at least 80% of the liver parenchyma (Fig. 1C). In areas of lower cellularity, the tumor was composed of spindle to oval cells arranged in a 'patternless' pattern amidst a collagenous stroma and intervening staghorn blood vessels (Fig. 1D). Within this area there was no significant nuclear pleomorphism and only very occasional mitotic figures were identified. In other areas the tumor was hypercellular, composed of loose fascicles of mildly to moderately pleomorphic spindle cells (Fig. 1E and F), in places with a herringbone pattern and very scanty background stroma (Fig. 2A). The mitotic count in these areas was 5-7 mitoses per 10 HPF. Areas of myxoid change and infarction/necrosis were also seen (Fig. 2B and C).

 

Immunohistochemically, the tumor cells were diffusely positive for BCL-2 (Fig. 2D) and CD99 with patchy expression of CD34 (Fig. 2E). They were negative for S100, CD10, smooth muscle actin (SMA), desmin, H-caldesmon, CD117, myogenin, cytokeratins, epithelial membrane antigen (EMA) and HepPar-1. Proliferation fraction assessed by mindbomb homolog 1 (MIB-1) was variable, approximately 10%-15% (Fig. 2F).

 

The morphological and immunohistochemical features were those of an SFT of the liver with variable patterns ranging from benign SFT to areas of histologically malignant transformation. In the absence of other lesions on imaging, this was considered to represent a primary SFT of the liver. The patient recovered from the operation uneventfully, and remains under follow-up with no evidence of recurrence in the first 16 months.

 

 

Primary SFT of the liver is a rare neoplasm which is similar to its counterparts in thoracic and other extrathoracic locations, sharing the characteristics histological and immunohistochemical features. Approximately 10%-15% of intrathoracic SFTs show malignant features histologically and/or in terms of clinical behavior, but such cases are rare at other sites including the liver.^[1] Histological features associated with aggressive clinical behavior include nuclear atypia, markedly increased cellularity, areas of necrosis and greater than 4 mitoses per 10 HPF. In a series of 92 patients with extrathoracic SFTs reported by Vallat-Decouvelaere et al,^[1] 10 had either recurred or had at least one atypical histological feature. Of these patients, 8 experienced a relapse, either local recurrence or a distant metastasis, highlighting the importance of long-term follow-up.

 

Primary SFT of the liver has been described in a small series^[2] and case reports with just over 42 cases.^[3-16] It can present with a painless mass, abdominal pain/discomfort, abdominal distension or hypoglycemia. It can also be identified incidentally during physical examination or imaging.^[2-9] Moran et al^[2] described nine cases of primary hepatic SFT, of which 2 cases showed histologically atypical features, including marked cellular atypia and mitotic figures varying from 2 to 4 mitoses per 10 HPF. On review of the literature, 7 cases of malignant SFT occurring in the liver were identified with an occasional case report documenting malignant transformation into a fibrosarcoma.^[9-15] Table describes the clinical presentations and follow-up of these cases and compares these with the findings in the current case report. The majority of these cases presented with a large tumor size and later developed recurrences and distant metastasis.^[9-15]

 

This present report describes a case of primary hepatic SFT with histologically benign and malignant areas. The histological features of malignancy, in our case, included hypercellularity, necrosis and a mitotic count of 5-7 mitoses per 10 HPF (1 HPF=0.1734 square mm). Moderate cytological atypia was seen. At the time of presentation and surgery, no metastasis was identified on imaging. The lesion was completely excised, 1-2 mm from the surgical margin, and at present there is no evidence of relapse during a 16-month follow-up. However, a long-term follow-up is indicated for these cases as relapse can occur several years later.^[11]

 

Preoperatively, this entity is usually not included in the differential diagnosis due to lack of awareness of this neoplasm occurring in the liver. A preoperative liver biopsy may be helpful in clinching the diagnosis of SFT; however, due to the danger of seedling and tumor spread through needle tract,^{[17, 18]} a preoperative liver biopsy is usually not performed at our center if the tumor is operable. This case highlights the propensity of SFT to occur in a wide array of sites, and this lesion should enter the differential diagnosis of a spindle cell lesion in the liver. It also provides a further example of the malignant potential of this neoplasm. Complete excision and long-term follow-up are warranted in these cases.

 

 

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