Primary orbital liposarcoma: histopathologic report of two cases.

Liposarcoma is a malignant tumor of adipose tissue. Considered the most common soft tissue sarcoma in adults, orbital liposarcoma is extremely rare. Most cases of orbital liposarcoma are primary and rarely metastatic. We report two cases of primary orbital liposarcoma with clinical presentation, radiologic studies (available for one case), and detailed histopathologic features. A brief review of primary orbital liposarcoma is also presented.

INTRODUCTION

Liposarcoma is a malignant tumor of adipose tissue and considered to be the most common soft tissue sarcoma in adults.1 Liposarcoma of the orbit is rare with more than 40 cases reported in the literature to date. Most published cases are primary and very few are metastatic.2–6 A brief summary of published data on primary orbital liposarcoma (series of two cases or more) in English literature is presented in Table 1.6–11 In this paper, we present two cases of primary orbital liposarcoma which comprise the only cases that presented to our orbit and oculoplastic service in over 25 years of practice.

Table 1

Summary of published primary orbital liposarcoma series (of at least 2 cases) in the English literature

CASE REPORTS

Case 1

A 35-year-old healthy man presented with right lower lid swelling and diplopia of six-month duration. Ophthalmic examination revealed right lower lid fullness with superior displacement of his right globe, 6-mm right upper lid ptosis, and limitation of abduction. Radiologic studies suggested an inflammatory process and the initial diagnosis of the first incisional biopsy was orbital panniculitis. Six months later, a repeated larger tissue biopsy was performed and the correct diagnosis of cellular sclerosing well-differentiated liposarcoma was reached after consultation with two additional pathologists. The patient underwent right side exenteration with indefinite clear surgical margins. The tumor was comprised of fat cells and lipocytes with some nuclear atypia, scattered lipoblasts, and intervening dense collagen [Figures 1a and b]. The patient has been followed up for 4 years with no evidence of recurrence or metastatic disease to date.

Figure 1

(a) Well-differentiated liposarcoma from exenteration tissue of case 1 (H and E, ×100). (b) Higher magnification of the tumor with the characteristic lipoblasts indicated by arrows (H and E, ×200)

Case 2

A 36-year-old healthy man presented with progressive proptosis and mild pain in the left eye of one-year duration. Local examination of the left eye revealed a palpable mass in the left lower lid, mild proptosis of 10 mm, mild limitation of extraocular movements in all directions, and diplopia in left down gaze. Pupil examination showed an afferent pupillary defect in the left eye but the optic disc was normal.

Computed tomography showed an isodense intraconal mass attached to the posterior segment of the left globe with no evidence of bone destruction or calcification. Magnetic resonance imaging showed mixed signal intensity mass on the T2 image with fat suppression and intense contrast enhancing on the T1 image [Figure 2a].

Figure 2

(a) T1 axial magnetic resonance image showing contrast-enhancing orbital tumor in case 2 at first presentation (red arrow). (b) Myxoid tumor area with lipoblast in the mixed liposarcoma of the second case (H and E, ×400). (c) Another tumor area of well-differentiated liposarcoma (H and E, ×400). (d) T1 axial magnetic resonance image showing recurrent left orbital contrast-enhancing mass (case 2) extending between the left medial rectus muscle and optic nerve, approaching the orbital apex (red arrow)

Anterior and lateral orbitotomy without bone removal was carried out. The tumor was attached to the posterior globe and optic nerve inferiorly. Histopathology showed a lobular tumor consisting of proliferating spindle-shaped and stellate cells with several lipoblasts suspended within myxoid-rich matrix [Figure 2b] and complex vascular system of proliferating blood vessels. Areas of more differentiated fat cells were seen with several lipoblasts [Figure 2c]. Mitotic figures were rare and the tumor infiltrated the adjacent connective tissue and skeletal muscle fibers. This appearance was consistent with a mixed type liposarcoma: myxoid and well-differentiated subtypes.

The tumor recurred 10 months later [Figure 2d] and was managed by exenteration. The histopathology was identical to the original tumor. Genetic studies failed to identify the translocations seen in the myxoid type of liposarcoma.

DISCUSSION

Liposarcoma commonly involves the retroperitoneum, thigh, and inguinal areas, but it is rare in the orbit. It is believed to develop from mesenchymal cells rather than from a preexisting lipoma.112

Henderson11 combined his six primary orbital liposarcoma cases with previously published cases by Jacobiec et al.8 (five cases), Lane et al.7 (three cases), and McNab and Mosley9 (2 cases), and found the median age of occurrence was 31.5 years (range, 17 to 71 years). Henderson found that both genders were equally affected.11 Our cases were both males and they were 35 and 36 years, which is similar to the median age mentioned by Henderson.11

Liposarcoma produces a clinical picture that resembles other orbital tumors, including signs such as proptosis, eye displacement with or without diplopia in addition to optic nerve compression with pain, and impairment of vision if the tumor is located at the orbital apex.11 Cai et al. in their series of seven cases10 also suggested that there are no characteristic clinical findings or diagnostic tests that are specific for liposarcoma. Patients with orbital tumors may present with a slowly developing mass, proptosis, diplopia, visual impairment, and possible pain.

The presence of lipoblast is essential for the pathologic diagnosis.12 It has been classified into the following five subtypes: well-differentiated, myxoid, round-cell, dedifferentiated, and pleomorphic.1 The myxoid type is thought to be the most common orbital liposarcoma as observed by Henderson.11 Based on the summarized data of 23 cases—with well-documented histopathologic typing of the tumor—from Table 1and our additional two patients, we can conclude that the most common type is myxoid (12 cases) followed by well differentiated in 10 cases. Other types, such as pleomorphic and dedifferentiated, are rare.

Another classification based on karyotyping divides liposarcoma into the following three main subtypes: well-differentiated and its subtypes (12q13-15), myxoid/round (12 : 16 translocation), and pleomorphic with complex karyotyping.13

Well-differentiated and myxoid liposarcomas generally have a benign course in contrast to round cell and pleomorphic liposarcomas which are aggressive.14 Recurrence is common as seen in our second case and in a case reported by Wagle et al.15 Both cases showed myxoid liposarcoma (with well-differentiated areas in our case) and recurrence in the first year after local excision which was managed by exenteration.15

Regional or distant metastases are rare.14 The prognosis for orbital liposarcoma appears to be relatively favorable, likely due to the small tumor size and predominantly well-differentiated histology.12 This is seen in case 1 who remains alive and healthy 4 years following his surgery, despite the delay in diagnosis and treatment. Ophthalmologists and pathologists should consider orbital liposarcoma during evaluation of a slow-growing orbital mass.