Ординатура / Офтальмология / Английские материалы / Imaging of Orbital and Visual Pathway Pathology_Muller-Forell_2005

6.3

Extraconal Area

Defined as the orbital space outside the muscle cone, the only “organs” of the extraconal space are fat and the lacrimal gland. However, this orbital compartment is the first section that orbital or extraorbital (nasal/paranasal) tumors and infections invade on their way to deeper orbital and even intracranial structures.

6.3.1 Tumors

6.3.1.1 Rhabdomyosarcoma

The orbit is the most common location in children, with 40% of all head and neck tumors appearing there (Barkovich 2000). The most common, malignant, soft-tissue tumor in childhood with up to 4%– 8% of all pediatric (less than 15 years old) malignant tumors is rhabdomyosarcoma. The incidence of rhabdomyosarcoma ranges from 1% to 4% of all biopsied orbital lesions, with a slight predilection for boys over girls (5: 3); the average age at diagnosis is 7 to 8 years old (Jones et al. 1965; Ellenbogen and

Lasky 1975; Grosfeld et al. 1983; Chin and Wei

1993; LeGall et al. 1994), but older patients may also be affected (Fig. 6.86). The tumor is mostly unilateral and,in some cases,may originate in the adjacent sinonasal region (Figs. 6.86, 6.87). Rhabdomyosarcoma may invade the skull base as well as the cavernous sinus and middle cranial fossa by growth along the orbital fissures (Sartor 1992; De Potter et al. 1995; Mafee 1996; Barkovich 2000). The characteristic clinical presentation of orbital rhabdomyosarcoma is rapidly progressing exophthalmos with dislocation of the eye, disturbance of motility, sometimes combined with unilateral ptosis (Fig. 6.88) (Gloor and Klaman 1992; Shields and Shields 1993). The tumors arise from primitive, undifferentiated mesenchymal cells and can be divided histopathologically into four different subgroups: (a) embryonal, (b) pleomorphic, (c) alveolar, and (d) botryoid rhabdomyosarcoma, with the alveolar tumor being the more malignant variant, characterized by anaplastic tumor cells spreading along soft-tissue septa or in the central cavity (Hogan and Wood 1972; Holbach et al. 1989). Conventional H&E staining as well as immunohistochemistry with detection of myoglobin and desmin support the diagnosis (Por-

terfield and Zimmerman 1962; Hirashima et al. 1986; Sun et al. 1990).

Rhabdomyosarcoma is frequently accompanied by conjunctival swelling and redness of the eye, suggesting an inflammatory rather than a neoplastic process (Sartor 1992). Delayed diagnosis may confront parents and physicians with an extremely rapidly growing tumor, and in rare cases with total destruction of the orbit. The majority of orbital rhabdomyosarcoma is found in the superior medial orbit (Fig. 6.89), mainly occupying the intraand extraconal compartment. Since no lymph vessels exist in the orbit, lymphogenous spread in regional lymph nodes and/or lymphatic metastasis is rare, and only seen in cases of tumor invasion into the eyelid and the conjunctiva. Extraorbital metastasis, especially into the lung,occurs by hematogenous spread (Liebner 1976;

Gehan et al. 1981; Adhikary and Fitzmaurice

1982; Wiener 1994; Sohaib et al. 1998).

While ultrasound and Doppler technology provide information on vascularization,they are,nevertheless, insufficient to establish the diagnosis. CT and (superior) MRI on the other hand give precise information about tumor size and the extent of tumor growth that may be both intraconal and extraconal, and possibly involve bone with destruction. On CT, the usually well-outlined tumor is isodense to the orbital muscles, showing significant contrast enhancement, because of its high vascularization (Fig. 6.90) (Wende et al. 1977; Gado and Smith 1978; Scotti and Nash 1982; Hopper et al. 1992). MRI shows long T1 and T2 characteristics with moderate to marked signal enhancement after i.v. gadolinium (Figs. 6.86–6.89, more prominent on fat-suppressed images (Figs. 6.86–6.89) (Sartor 1992; Cooper et al. 1994; Barkovich 2000; De Potter et al. 1995; Yang et al. 1997; Mafee et al.

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Fig. 6.86a–g. A 36-year-old woman with pressure sensation and a reddish, swollen left eye; no double vision. Diagnosis: rhabdomyosarcoma of the left ethmoid. Axial CT: a View of the medial orbit with destruction of the medial orbital wall by a medially extending ethmoidal tumor. b Upper orbit with additional infiltration of the skull base at the site of the cribriform lamina. MRI: c axial T2-weighted image, corresponding to a, demonstrating left-sided proptosis. Tumor infiltration is seen in the lamina papyracea and the nasal bone, and (hyperintense) mucous retention in the ipsilateral region of the sphenoid sinus. d Corresponding T1-weighted native view, superior visualization of the extraconal intraorbital extension with suspected infiltration of the tendon of the left medial rectus muscle. e Corresponding T1-weighted, con-

1998). The differential diagnosis of rapidly growing capillary hemangioma is sometimes difficult (De Potter et al. 1995) and should include neuroblastoma, lymphoma, metastasis, as well as aggressive idiopathic orbital inflammation (Sartor 1992).

Surgical biopsy and histopathologic confirmation should be performed even under emergency conditions and are mandatory for the definite diagnosis and acute planning of therapy. The conventional regimen of surgical removal of the tumor followed

by radiotherapy (30–60 Gy) has been substituted by chemotherapy (VAC – vincristine, actinomycin D, and cyclophosphamide), which was demonstrated to lead to successful remission and a survival rate of 93% (Rousseau et al. 1994). Radiotherapy harbors the risk of radiation-induced secondary tumors, leukoencephalopathy, cataract, retinopathy, and orbital deformation with enophthalmos (Van den Bogaert et al. 1992; Sagerman 1993; Regine et al. 1995).

6.3.1.2 Hemangiopericytoma

Hemangiopericytomas are rare, uncommon, ubiquitous, highly vascular tumors, originating from cells (Zimmermann’s pericytes), which are arranged around capillaries and postcapillary venules (McMaster et al. 1975). Although the orbit is a rare location, hemangiopericytomas prefer the superior part of the orbit (Croxatto and Font 1982). They become clini-

cally manifest as slowly progressing proptosis or lid swelling (Fig. 6.91). There is no gender predominance, the mean age of presentation is the 4th decade of life, and recurrences of the mostly (50%) benign tumor are known in about 30% of patients (McMaster et al. 1975; Henderson and Ferrow 1978). Histologically, hemangiopericytomas consist of numerous sinusoidal vascular spaces, lined with flat to ovoid endothelial cells and surrounded by proliferating pericytes (Karcioglu et al. 1997; Bilaniuk 1999). Because of

Orbital Pathology

the frequent recurrence, but also metastasis of this usually benign tumor, complete surgical excision is recommended (Sullivan et al. 1992b; Karcioglu et al. 1997; Cascone et al. 1998).

Imaging demonstrates a soft-tissue, well-circum- scribed, generally encapsulated and occasionally lobulated,markedly enhanced mass.An irregular margin is seen in tumors that infiltrate adjacent tissue,including muscles and bone (Fig. 6.92), and is best identified on CT. MRI best enables a complete delineation of the lesion, presenting isointense with slight contrast enhancement on T1-weighted images and with variable isoto hyperintense signal on T2-weighted series (Fig. 6.91).

In addition to the extraconal location and isointensity on T2-weighted images, a dense tumor stain on angiography (if performed) is one of the most important differential diagnostic criteria of cavernous hemangioma. Cavernous hemangioma shows a highintensity signal caused by its blood content, delayed contrast enhancement on MRI, but no contrast stain on angiography (Kikuchi et al. 1994a; Bilaniuk 1999). The differential diagnosis of hemangiopericytoma includes among others fibrous histiocytoma, mesenchymal chondrosarcoma, hemangioendothelioma, leiomyosarcoma, malignant schwannoma, and liposarcoma (Rootman 1988).

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6.3.1.3

Neurinoma, Neurofibroma

Neurinoma, benign tumors of the peripheral nerve cells, may involve the orbit not only in the intraconal space (Figs. 6.40, 6.41), but also extend/involve the extraconal area, where they may present as encapsulated, well-defined lesions presenting with unspecific symptoms or cranial nerve palsy (Fig. 6.93). In the presence of sphenoid bone dysplasia, additional multiple, clustered masses, presenting with marked contrast enhancement, neurofibroma should be considered as a possible diagnosis, as in the case of a previously unknown neurofibromatosis type 1 without further clinical signs (Fig. 6.94).

6.3.1.4

Secondary Tumors (Sinus-Nasal Malignancies, Metastasis, Olfactory Neuroblastoma, Miscellaneous)

6.3.1.4.1

Sinus-Nasal Malignancies, Metastasis

Any sinus lesion that is inflammatory or neoplastic, may involve the orbit secondarily. Carcinoma of the maxillary sinus is the most common sinus neoplasm

to invade the orbit (Fig.6.95).These malignant tumors may not only infiltrate the orbit but also extend to the endocranium (Fig. 6.96). Metastatic involvement of the orbit is known to be the first manifestation of an occult primary malignant tumor in 30%–50% of cases, accounting for less than 5%–11% of all orbital tumors (Moss 1962; Rootman 1988). The most frequent primary tumors are breast (Fig. 6.97), lung, and prostate carcinoma (Fig. 6.98), while metastases

of neuroblastoma (Fig. 6.99) or orbital infiltration of extraorbital melanoma (Fig. 6.100) are extremely rare (Zakka et al. 1980; Rootman 1988). As the ophthalmic presentation of metastatic disease is varied (including exophthalmos and enophthalmos, ptosis, motility disorders, and papilledema), clinical symptoms of pain and dysesthesia are highly suggestive of neoplastic lesions growing on a sensory nerve. If infiltrative tumor growth is combined with evidence

of irregular bony destruction, biopsy and systemic work-up are needed to make a definite diagnosis (Casper et al. 1993).

Neuroblastoma in childhood arises, as a rule, primarily in abdominal organs, but represents the second most frequent malignant orbital tumor after rhabdomyosarcoma in this patient group (Casper et al.1993). Primary neuroblastoma originating in other locations as, e.g., in the maxillary bone (Fig. 6.101) is relatively

rare. Clinical symptoms of acute, painful proptosis combined with unilateral ecchymotic swelling of the lid are guiding symptoms for the most frequently bilateral metastasis of neuroblastoma, which primarily involves the abdominal organs. The diffuse, in up to 40% bilateral tumor infiltration of the sphenoid wing and intracranial, pachymeningeal tumor involvement (Fig. 6.99) are characteristic for the orbital presentation of neuroblastoma (Casper et al. 1993).