Orbital fibrous histiocytoma: computed tomography in 10 cases and a review of radiological findings

Undifferentiated Pleomorphic Sarcoma Metastatic to the Orbit

Undifferentiated pleomorphic sarcoma is a malignancy of mesenchymal origin, which was previously known as malignant fibrous histiocytoma. It is known to occur on rare occasion as a primary orbital tumor, but no known cases of metastatic orbital involvement have been reported since 2002, when the reclassification of these tumors took place. The authors report a patient who presented with a metastasis to the left orbit 2 years after undergoing treatment of a high-grade undifferentiated pleomorphic sarcoma of the right thigh. Histopathology of the orbital mass was similar to the primary tumor biopsy prior to neoadjuvant chemotherapy and radiation. The appearance was markedly altered in the subsequent excisional tissue, which showed treatment changes. Immunohistochemistry and genetic testing also supported the metastatic nature of the orbital lesion. The patient's tumor progressed rapidly despite systemic targeted therapy and orbital exenteration was performed. At 2 years follow up, the patient remained without evidence of tumor recurrence in the socket.

[Undifferentiated high-grade pleomorphic sarcoma of the orbit: a case report]

CASE REPORT

A 27-year-old female presented to us with a complaint of proptosis of her right eye. Imaging tests showed an extraconal mass in the medial orbital wall, which affected the medial rectus. The tumor was removed and adjuvant radiotherapy was required. The histological examination showed an undifferentiated high-grade pleomorphic sarcoma of the orbit. There has not been recurrence after 6 years of follow-up.

DISCUSSION

Undifferentiated high-grade pleomorphic sarcoma is an uncommon cause of malignant orbital mass. It grows fast and can metastasize, so extension studies are required. Surgical excision is the treatment of choice.

[Mesenchymal orbital tumors]

Mesenchymal tumors grow from pluripotent mesenchymal cells that form the soft orbital tissue. Primary tumors of the orbital walls are discussed in another section. Tumors from muscle and adipose tissue are rare or exceptional, except rhabdomyosarcoma, described in the section dedicated to pediatric tumors. Most frequent tumors are fibrous histiocytomas and solitary fibrous tumors, which often have a retrobulbar location. Fibrous histiocytoma is benign in only 65 % of cases. Fibrous solitary tumor is now better known (Ag CD34): this tumor is generally benign but frequently recurs.

Fibrous Histiocytoma of the Lacrimal Gland

Fibrous histiocytoma, a primary mesenchymal tumor of the orbit, is known to arise from various ocular and adnexal tissues. We are unable to find a published report of this tumor originating from the lacrimal gland. We report a case of a benign fibrous histiocytoma of the lacrimal gland in an 11 year old girl who presented with painless, progressive eyelid swelling and mild proptosis. Imaging studies revealed a discrete mass in the lacrimal gland region. The tumor was completely excised by anterolateral orbitotomy. Light microscopy showed a spindle cell tumor arising from the lacrimal gland. The tumor cells were arranged in a characteristic storiform (cartwheel) pattern with no pleomorphism or mitotic figures. Immunohistochemically, the tumor cells were focally positive for CD-68 and negative for S-100, smooth muscle actin, vimentin, and CD-34, which ruled out neurofibroma, leiomyoma, solitary fibrous tumor, and hemangiopericytoma. Based on these features, a diagnosis of benign fibrous histiocytoma was made.

Fibrous histiocytoma and fibrous tissue tumors of the orbit

Fibrous orbital tumors present clinically and radiographically in a broad spectrum ranging from a benign mass, to locally aggressive tumor, to invasive malignancy. Pathologic analysis and diagnosis are often challenging, usually based on a combination of light microscopy, immunohistochemistry, and electron microscopic findings. Some light microscopic and immunohistochemical findings, however, are relatively characteristic. A storiform or cartwheel pattern and vimentin staining are characteristic of fibrous histiocytoma. A herringbone pattern is usually found in fibrosarcoma. A "patternless pattern" and CD34 staining is found most commonly in solitary fibrous tumor. CT and MR imaging findings, as well as clinical presentation, in fibrous orbital lesions are often difficult to distinguish from those of other orbital masses, although there may be useful clues. Benign fibrous lesions are usually well-circumscribed and may chronically remodel bone, whereas more aggressive malignant fibrous tumors tend to have infiltrating margins and may destroy bone on CT or MR imaging. With malignant fibrous masses, enhancement patterns on CT or MR imaging may be more inhomogeneous, with avascular or necrotic nonenhancing regions. At MR imaging, benign lesions tend to be homogeneous on T1, T2, and postgadolinium T1-weighted images, whereas malignant soft tissue lesions may change their pattern from homogeneous on T1-weighted images to heterogeneous with low signal septations on T2-weighted images. Low T2 signal comprising part or all of a fibrous lesion correlates with dense collagen fibers, with a less cellular matrix. Areas of hyperintensity on T2-weighted images correspond with a more cellular matrix of fibroblasts and other cells. Calcification within a tumor, however, may give a similar appearance. Thus, if a lesion has predominantly low signal on T2-weighted images, or less specifically has low signal septations, then a fibrous orbital lesion with high collagen content may be ranked higher in the differential diagnosis (see Figs. 2E and 3B). When T2 signal is intermediate-to-high, then one has a difficult time narrowing the differential diagnosis. Radiographically, distinguishing these lesions from other fibrous orbital lesions, as well as from other varieties of orbital masses, is difficult. Differential diagnosis of fibrous orbital masses includes all the fibrous lesions described in this article, in addition to schwannoma (Fig. 7), neurofibroma (Figs. 4 and 8), hemangiopericytoma (Figs. 9 and 10), rhabdomyosarcoma, meningioma, lymphoma, and metastasis (Figs. 11 and 12). A history of prior orbital irradiation for retinoblastoma or other tumors may raise the possibility of radiation-induced secondary tumors, such as MFH, fibrosarcoma, and osteosarcoma. Determining the extent of orbital involvement remains the primary goal of the radiologist. The final diagnosis still rests with the pathologist.

Orbital masses

The "space approach" will be introduced as a means of analyzing orbital masses on imaging studies. Determination in which space an orbital mass resides, the character of its margin, the presence or absence of bony changes, and evidence of extension of the mass beyond the orbit often allows the radiologist to narrow the differential diagnosis and provides essential information to the ophthalmologist for definitive diagnosis and treatment planning.

Bilateral multiple cavernous haemangiomas of the orbit

Orbital cavernous haemangioma, a common orbital tumour, is usually single and unilateral. We report the first case of histologically confirmed bilateral multiple cavernous haemangiomas of the orbit.