Clinicopathological analysis of primary liposarcoma of the orbit
【摘要】 探讨眼眶原发性脂肪肉瘤的临床和病理特点。方法：收集2例眼眶原发性脂肪肉瘤和6例腹膜后原发性脂肪肉瘤的临床资料，病理标本光镜取材切片观察，免疫组织化学作CK(AE1/AE3), Desmin, MyoD1,S100protein, Melanoma标记。眼眶原发性脂肪肉瘤的例2 作透射电镜观察。结果：原发性眼眶脂肪肉瘤的患者年青，原发性腹膜后脂肪肉瘤的患者年龄以40岁以上者为主（5／6）。原发性眼眶患者症状显著但肿瘤小，原发性腹膜后患者症状轻，但肿瘤巨大。两组在组织学上分布于脂肪肉瘤的各型。肿瘤易复发，但无转移。结论：眼眶原发性脂肪肉瘤易复发，诊断依靠光镜和电镜观察以及免疫组织化学染色。
【关键词】 脂肪肉瘤 眼眶 腹膜后 恶性冬眠瘤 免疫组织化学 电镜
INTRODUCTION
Primary liposarcoma of orbit is extremely rare[16]. We reported 2 cases of orbital liposarcoma who presented with proptosis, and compared with 6 cases of primary retroperitoneum liposarcoma.
MATERIALS AND METHODS
Tissue was fixed in 40g/L buffered formalin, routinely processed, and paraffin embedded. For immunohistochemistry, 3μm thick sections were cut and mounted on polyllysine coated glass slides. The sections were heated for 10 minutes at 60℃ and dewaxed. Antigen retrieval was achieved by microwave pretreatment in a 0.01mol/L trisodium citrate (bihydrate) solution (pH=6.0) for 10 minutes at 85℃. Sections were stained with monoclonal antigen of CK(AE1/AE3), desmin, MyoD1,S100protein, melanoma.
Ultrastructural examination was performed on fresh tissue of primary liposarcoma of orbit in case 2. Tissue was fixed in 25g/L glutaraldehyde, postfixed in 10g/L buffered osmium tetroxide, and embedded in epoxy resin. Sections (1μm thick) were stained with toluidine blue. Ultrathin sections for electron microscopy were stained with potassium permanganate, uranyl acetate, and lead citrate.
RESULTS
Clinical Data
Clinical examination of primary liposarcoma of orbit Case 1: a 30yearold male presented with decrease of vision of left eye in 2year duration and exophthalmos of left eyeball for 2 months. On examination, there was proptosis of the left eye; visual acuity was 4/18 in the left eye and normal in the right eye. Systemic examination revealed no tumor at any other sites. Chest Xray and ultrasound of abdomen were normal. He underwent tumor excision.
Case 2: a 16yearold young lady presented with progressive proptosis of right eye orbit and declined vision for four months. External examination showed a swelling in the right orbit, with downward and medial displacement of the eyeball. There was proptosis, gross chemosis, external ophthalmoplegia.MRI showed illdefined intraconal mass lesion involving muscle in right orbit. Lesion was seen around the optic nerve. The mass was excised completely. She was scheduled for radiotherapy after the operation. Three months later, the tumor recurred locally. She presented with unilateral headache and diminished vision of right eye again. On examination there was a mass in the upper right eyelid. MRI showed a mixed intensity retrobulbar mass that was displacing the eyeball anteriorly. Orbital exenteration was done with a pathological diagnosis of liposarcoma.
Clinical features of primary liposarcoma of retroperitoneum The patients were three men and three women aged 3774; the average was 47 years old. They presented with abdominal mass, pain, poor appetite and nausea during two months to three years.
All patients underwent tumor excision. Only two patients subsequently developed recurrent tumors. One was at 1 year postoperatively, the other was at 5 years postoperatively. None of them had metastases. Systemic examinations of preoperation and postoperation of these patients revealed no tumor at any other sites and there were not palpable turgescent lymph nodes.
Pathological Examination On gross inspection of primary liposarcoma of the orbit, the biopsy specimen of case 1 received in two pieces was greyishwhite and soft in consistency, measuring 2cm×2cm when aggregated. In case 2, the biopsy specimen of first operation received in two pieces was greyishwhite, measuring 3.7cm×1.8cm×1cm and 4cm×3cm×1.8cm. The mass of second operation was multilobular, firm and measuring 7cm×5cm×3cm.
On gross inspection,the mass of primary liposarcoma of retroperitoneum was multilobular,greyishwhite, firm, measuring from 17cm×15cm×11cm to 48cm×33cm×6cm.
Histological Observation Histological examination of primary orbit liposarcoma in both cases showed different features. Case 1: microscopically the tumor was characterized by round balllike aggregates of cells, at the periphery of which were delicate thinwalled blood vessels and fine fibrous septa. The cells in the center of the cluster lose their cohesiveness and fall away, leaving the peripheral cells lining the fibrous septa. The component cells were like roughcast glass in appearance and marked by fine granular eosinophilic cytoplasm(Figure 1). Mitosis was 5/50HPF. Among these tumor cells, typical univacuolated and multivacuolated lipoblasts were seen.
In case 2, the tumor was composed of spindle cells and adipocytes of varied shapes. These lipoblasts were of varied sizes and contained multiple vacuoles that were indenting the nuclei. Characteristic myxoid stroma and thinwalled capillaries were present in the tumor tissues (Figure 2). Mitosis was 18/50HPF. Tumor infiltrated the optic nerve and eyeball.
The pathological diagnosis was malignant hibernoma of case 1 and myxoid liposarcoma of case 2.
Histological examination of 6 cases of retroperitoneum liposarcoma was made. They were subdivided into four types: one case was well differentiated;two cases were myxoid; two cases were pleomorphic; and one case was dedifferentiated. The link between the various types of liposarcoma was the lipoblast. It showed univacuolated or multivacuolated lipoblasts as was observed in each case of retroperitoneum liposarcoma. Mitosis conditions were 0/50HPF in well differentiated,16/50HPF in pleomorphic, 5/50HPF in dedifferentiated, 23/50HPF in myxoid. Focal areas of dedifferentiated sarcoma were malignant fibrohistosarcoma. Large areas of coagulative necrosis were present.
Immunohistochemistry The tumor cells of two groups were immunopositive for S100 protein but were negative for CK(AE1/AE3), Desmin, MyoD1, Sacomeric, Melanoma.
Ultrastructure Examination Case 2 of primary liposarcoma of orbit showed lots of lipid drops wrapped by unit membranes, and a few of other subcellular compartments or organelles under electron microscope, such as mitochondria, endoplasmic reticulum, Golgi apparatus, lysosomes(Figure3,4).
DISCUSSION
Despite their frequency among the malignant tumors of soft tissues, liposarcomas are still rare tumors, being about 100 times less common than benign lipomas [7]. There were only 6 cases of primary retroperitoneum liposarcoma in our department from 2000 to 2007 and only 2 cases of primary orbit liposarcoma were detected during 35 years.
Welldifferentiated tumor of retroperitoneum liposarcomas is rare in our group (only one case), while poorly differentiated tumors are common (5 cases). Radical resection surgery is generally regarded as the treatment of choice for liposarcoma. Most of the retroperitoneum liposarcomas cannot be completely excised. Recurrence is common (2 cases in our group). However, regional or distant metastasis is rare (none in our group). The overall course of disease is slow.
The orbit is a rare site for primary liposarcoma[1,35]. In our group, one patient was 17 years old, while the other was 30 years old. Compared with the average patient age of 47 years in primary retroperitoneum liposarcoma, orbital liposarcoma has been shown to occur in younger patients. Patients present with proptosis and occasionally decrease of vision. The tumors involve the retrobulbar fat and the optic nerve and cannot be completely excised. Recurrence is common (For example, case 2). Orbital exentration is primary treatment of choice.
Histologically, as observed in case 2, the myxoid liposarcoma showed a myxoid interstitium with lipoblasts and a delicate capillary network. The first case was a malgnant hibernoma, which showed predominantly round balllike aggregates of cells with granular eosinophilic cytoplasm. Differential diagnosis includes alveolar soft tissue sarcoma, embryonic rhabdomyosarcoma, and malignant melanoma. The tumor cells of malgnant hibernoma were immunopositive for S100 protein but were negative for Sacomeric, Desmin, MyoD1, Melanoma.Among the tumor cells, lipoblasts were seen.
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