Fibromatoses

Fibrohistiocytic tumors include benign and malignant neoplasms as well as a variety of nonneoplas-tic proliferations that are collectively termed reactive fibromatoses. These lesions are currently considered to originate from primitive mesenchyme as a result of its differentiation into multiple cell lines (Figure 15.1).1,2 Common fibromatoses of the head and neck include desmoid-type fibromatosis, juvenile fibromatosis (aggressive infantile fibro-matosis),3 and nodular fasciitis.4 Desmoid-type fi-bromatosis and nodular fasciitis are also known as aggressive fibromatoses.5'6 Most fibromatoses tend to involve fascial tissues of the trunk and extremities. These tumors are rarely seen in the head and neck area, but when they occur in the oronasal cavities, sinuses, and orbit, they are difficult to diagnose and treat. These lesions may seem to be histopathologically benign but are often locally aggressive and have a high rate of recurrence, particularly in relatively restricted anatomic regions such as the orbit. They often lead to the functional compromise of adjacent anatomic structures and in many instances recur postsurgically, requiring further treatment.

Schutz et al. report desmoid-type fibromatosis in a 63-year-old woman who presented with an intraorbital mass with extension toward the apex of the orbit.5 Although the lesion was histologically classified as fibro-matosis, its clinical behavior was aggressive, with invasion of orbital tissues and bone. In view of this and the known tendency for tumor recurrence, the patient's eye was exenterated. Another example of a desmoid-type lesion is described by Henderson in a 5-year-old boy who presented with proptosis and papilledema.7

Juvenile fibromatosis of the orbit and periorbital region was reported by Hidayat and Font in six patients ranging from 1 to 11 years of age.8 The majority of lesions presented in the lower eyelid and infe rior orbital area. Extension of three tumors to the underlying periosteum was documented; none metasta-sized, but two of six lesions recurred after surgical excision.

Nodular fasciitis is another fibroproliferative lesion, sometimes termed pseudosarcoma.4,9 It usually forms a discrete soft tissue mass, partially fixed to adjacent soft tissues; about 10% of all cases occur in the head and neck area. In a large series of 163 pseu-dosarcomas of the head and neck, 13 were reported in the orbit and periorbital tissues.9 Most of these lesions develop in the eyelids rather than the orbital cavity.10 When nodular fasciitis develops within the orbit or periorbital area, it usually presents as a well-circumscribed, painless, firm, and movable tumor. Such lesions are not difficult to excise in toto because they are well delineated, and complete excision of nodular fasciitis is usually curative.11,12 Histopathologically, the lesion consists of irregular bundles or individual fibroblasts within a myxoid matrix. Although the fi-broblastic areas share the same appearance as the fibroblasts of giant cell fibroblastoma (GCF), multinu-cleated giant cells are rarely seen in nodular fasciitis. While some of these lesions may appear aggressive histopathologically, the overall recurrence rate is reported to range from 1 to 2%.9

The neoplastic group is somewhat easier to classify but may be similarly difficult to manage clinically. The two major categories are fibroblastic and fi-brohistiocytic tumors. Fibroblastic neoplasms can be benign or malignant and comprise collagen-synthesizing fibroblasts and/or fibrocytes; examples include fibroma, fibromyxoma, solitary fibrous tumor (SFT), GCF, and fibrosarcoma.13,14 These fibroblastic tumors may occasionally develop in the orbit, but not as often as their fibrohistiocytic cousins, which frequently present as primary orbital tumors. The neoplasms originating exclusively from fibroblasts, namely, fibroma and fibrosarcoma, are the least commonly encountered orbital tumors. Fibromas can be difficult to differentiate from loosely organized fibrous tissue. Fibrosarcoma of the orbit is rare and is primarily encountered as a second malignant neoplasm in hereditary retinoblastoma patients following radiation treatment.15 Although some fibrosarcomas are well delineated, others infiltrate the orbital tissue haphaz

PRIMITIVE MESENCHYME

PRIMITIVE MESENCHYME

fibroma/fibrosarcoma desmoid-type fibroxanthoma benign fibrous eiastofibroma juvenile type fibromyxoma histiocytoma giant cell fibroblastoma nodular fasciitis reticulohistiocytoma malignant fibrous histiocytoma dermatofibrosarcoma protuberans (DFSP)

FIGURE 15.1. The origin of cells leading to fibrohistiocytic tumors.

fibroma/fibrosarcoma desmoid-type fibroxanthoma benign fibrous eiastofibroma juvenile type fibromyxoma histiocytoma giant cell fibroblastoma nodular fasciitis reticulohistiocytoma malignant fibrous histiocytoma dermatofibrosarcoma protuberans (DFSP)

FIGURE 15.1. The origin of cells leading to fibrohistiocytic tumors.

ardly, whether they originate within the orbital cavity as a primary tumor or extend there by contiguity (Figure 15.2).

Fibromyxomas are tumors of primitive mesenchy-mal cells, composed of a scanty population of spindle cells scattered within a myxomatous matrix of mucin. These benign lesions very rarely develop as solitary tumors in the orbit but more often extend into the orbit secondarily (Figure 15.3). In surgery, even the benign lesions infiltrate to adjacent tissues and therefore are difficult to resect. They tend to recur frequently. It is rare to have a malignant fibromyxoma, but the entire specimen should be examined to rule out focal malignancy.

Fibrohistiocytic tumors are a diverse group of neoplasms, primarily composed of fibroblastic and histio-cytic cells. Most authorities believe these tumors originate from a multipotential primitive mesenchymal cell that can differentiate fibroblastic and fibrohistio-cytic cell lines.9,16

Fibrous histiocytoma, the most commonly encountered mesenchymal orbital tumor in adults, may be benign, locally aggressive, or malignant.17,18

Although this lesion usually presents with a mixture of fibroblastic and histiocytic cells, it has a broader range of histopathologic appearance. In certain aggressive forms, multinucleated giant cells may be mixed with spindle cells of fibrous histiocytoma. Clinically, the differential diagnosis includes other solid mesenchymal tumors such as leiomyoma, neuri-lemoma, hemangiopericytoma, and rhabdomyosar-coma.19,20 Computed tomography (CT) and magnetic resonance (MR) imaging are not very rewarding for distinguishing fibrous masses such as fibrous histiocy-toma from orbital tumors of other types.21,22 As a rule, benign lesions are well delineated and remodel the bone because of chronic compression (Figure 15.4). Malignant fibrous lesions tend to show infiltrating margins like other malignant soft tissue tumors (Figure 15.5). Enhancement patterns of CT and MR im

FIGURE 15.3. (A,C) A well-encapsulated maxillary fibromyx-oma extending secondarily into the inferior orbit (B); arrows point to the apex of the tumor which was abutting the globe. (D) Histo-pathologic preparation shows a mixture of elongated fibroblast-like cells mixed with myxomatous matrix.

aging that may vary according to tissue type of the tumor are summarized in Table 15.1.22

Fibrous histiocytoma usually presents a heterogeneous, isointense to hyperintense signal with respect to extraocular muscles on Tl-weighted studies. Following administration of GDPA enhancement of the tumor is usually heterogeneous. Other soft tissue tumors in the orbit can produce CT and MR features similar to those of fibrohistiocytoma, except for tumors of vascular origin, which enhance markedly and homogeneously.21 Malignant fibrous histiocytoma has been described as second primary malignancy in children with hereditary retinoblastoma.23

Dermatofibrosarcoma protuberans (DFSP) is best known as an aggressive form of fibrous histiocytoma with indeterminate malignant potentials. DFSP con

FIGURE 15.5. (A) Malignant fibrous histiocytoma presenting with shows the aggressiveness of the tumor with numerous mitotic fig-massive downward proptosis. (B) Gross specimen of the tumor re- ures (single arrow) and pleomorphic tumor cells (joined arrows). veals a "firm" appearance of the cut surface. (C) Histopathology also

FIGURE 15.5. (A) Malignant fibrous histiocytoma presenting with shows the aggressiveness of the tumor with numerous mitotic fig-massive downward proptosis. (B) Gross specimen of the tumor re- ures (single arrow) and pleomorphic tumor cells (joined arrows). veals a "firm" appearance of the cut surface. (C) Histopathology also sists of fibroblast-like spindle cells. Xanthogranulomatous lesions may present diagnostic problems because of the presence of Touton-type giant cells, particularly when intermingled with a fibroblast-like spindle cell population. Where there is an absence of Langerhans cells, however, these tumors can be definitively differentiated from true histiocytic lesions because of the absence of Langerhans cells.24,25

Solitary fibrous tumor is a visceral spindle cell tumor that can also be seen in the orbit.25 Clinically, it presents as a slowly growing, well-circumscribed intraorbital lesion.26 Arteriograms have demonstrated these tumors to be very vascular and difficult to differentiate from other well-vascularized orbital lesions such as fibrous histiocytoma, hemangiopericytoma, and paraganglioma. Standardized ultrasonography, CT and MR imaging are not very helpful in differentiating SFT from other solitary vascular lesions. The most accurate way to diagnose this lesion is to perform a biopsy and examine the tissue with hematoxylin-eosin and immunoperoxidase stains; SFT shows diffuse and strong positivity for vimentin and CD34. Occasionally these tumors present with aggressive growth and may infiltrate the orbital bones and recur after excision.27 Giant cell fibroblastoma is another fibrous tumor that is histologically benign without potential for distant metastasis, but it may behave clinically as an in-

filtrative tumor (Figure 15.6), which makes management difficult.28-30

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