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Orbital solitary fibrous tumor: A report of two cases
Taiwan Journal of Ophthalmology 3 (2013) 120e122
Contents lists available at SciVerse ScienceDirect
Taiwan Journal of Ophthalmology journal homepage: www.e-tjo.com
Case report
Orbital solitary fibrous tumor: A report of two cases Wai-Man Cheang a, Li-Chen Wei a, *, John Wang b, Hin-Yeung Tsai a a b
Department of Ophthalmology, Taichung Veterans General Hospital, Taichung, Taiwan, ROC Department of Pathology, Taichung Veterans General Hospital, Taichung, Taiwan, ROC
a r t i c l e i n f o
a b s t r a c t
Article history: Received 8 January 2013 Received in revised form 23 April 2013 Accepted 13 May 2013 Available online 25 June 2013
Solitary fibrous tumor (SFT) is a rare spindle-cell neoplasm that can be found in the orbit. Here, we report two cases affected by orbital SFT. Both patients were female, aged 52 years and 59 years, respectively, and had experienced a painless unilateral orbital lesion. Computed tomography (CT) imaging revealed a wellcircumscribed and contrast-enhanced soft tissue mass simultaneously. The tumors were located in the laterotemporal extraconal space of the right orbit and the inferior portion of the left orbit, respectively. Both patients underwent complete resection of their tumors. The histological findings showed alternating hypercellular and hypocellular areas composed of bland spindle cells with a fibrous stroma. The strong immunoreactivity for CD34 supported the diagnosis of orbital SFT. There was no recurrence at the 2-year and 3-year follow-up visits, respectively. SFTs should be considered in the differential diagnosis of an orbital tumor. The combination of a CT scan, histologic findings, and immunohistochemical staining will provide an accurate diagnosis. En bloc excision of the tumor is the mainstay of treatment in order to avoid recurrence. Copyright Ó 2013, The Ophthalmologic Society of Taiwan. Published by Elsevier Taiwan LLC. All rights reserved.
Keywords: immunohistochemical staining orbital solitary fibrous tumor surgery
1. Introduction Solitary fibrous tumors (SFTs) arise from mesenchymal cells or fibroblasts. They usually present in the pleura, but recently a few cases involving the orbit have been described.1,2 Patients with an orbital SFT may present with unilateral, painless, slowly progressive proptosis or a palpable mass in the periocular area. Computed tomography (CT) scanning and magnetic resonance imaging (MRI) reveal a well-circumscribed, contrast-enhanced soft tissue mass.3 Histological examination and positive CD34 immunoreactivity are useful in discriminating SFTs from other tumors.4,5 Here, we report two cases of orbital SFT. 2. Case reports 2.1. Case 1 A 52-year-old woman developed gradual proptosis of the right eye over several months. On ophthalmic examination, her visual acuity was 6/6.7 in the right eye. There was upward and lateral
limitation of right ocular movement. The lesion caused an inferior displacement of the eyeball and exophthalmos (Fig. 1A). Hertel exophthalmometry gave readings of 16.5 mm for the right eye and 13 mm for the left eye. CT scans revealed a contrast-enhanced solitary mass located in the lateral extraconal space of the right orbital cavity without bony erosion (Fig. 1B). A lateral orbitotomy was performed. The mass was dissected and excised completely (Fig. 1C). The bone fragment was then replaced and secured with 3-0 nylon through pre-drilled holes. In its gross dimensions, the lesion was a 3.8 cm 3 cm 1.5 cm, thin, encapsulated, and well-circumscribed tumor. Microscopically, it revealed coexistent hypocellular and hypercellular areas separated by fibrous stroma (Fig. 1D and E). The hypercellular areas were composed of bland spindle cells with a storiform pattern. No mitotic activity or atypia cells were found. The subsequent immunohistochemical staining revealed CD34 positivity (Fig. 1F), Ki-67 positivity of less than 5%, and S100 negativity. The patient was free of recurrence at a 2-year post-surgical follow-up. 2.2. Case 2
* Corresponding author. Department of Ophthalmology, Taichung Veterans General Hospital, Number 160, Section 3, Chung-Kang Road, Taichung City 40705, Taiwan, ROC. E-mail address: [email protected] (L.-C. Wei).
A 59-year-old woman had developed a slowly progressing, palpable, painless mass over the infraorbital area of her left eye over the previous 3 years. Her visual acuity was 6/6.7 for the left eye.
2211-5056/$ e see front matter Copyright Ó 2013, The Ophthalmologic Society of Taiwan. Published by Elsevier Taiwan LLC. All rights reserved. http://dx.doi.org/10.1016/j.tjo.2013.05.004
W.-M. Cheang et al. / Taiwan Journal of Ophthalmology 3 (2013) 120e122
121
Fig. 1. (A) Upper eyelid swelling, proptosis, and medial inferior deviation of the globe is noted in the patient’s right eye. (B) Coronal CT scan reveals a contrast-enhanced mass (*) next to the lacrimal gland (arrow) in the lateral extraconal space of the right orbit, causing downward displacement of the globe. (C) The 3.5 cm mass is dissected and removed completely. (D) Photomicrograph showing diffuse spindle cells and collagen deposition (magnification 200). (E) Histology reveals the deposition of abundant collagen fibers and hypercellular (arrowhead) and hypocellular (asterisk) areas (magnification 100). (F) Immunohistochemical staining shows positivity for CD34 (magnification 200).
Findings relating to extraocular movement, pupillary examination, and Hertel exophthalmometry were unremarkable. CT scans revealed a well-enhanced orbital mass located at the left inferior aspect of the orbit (Fig. 2). The patient underwent anterior orbitotomy via the lower eyelid. A 2 cm 1.5 cm 1 cm, tan-colored, wellcircumscribed tumor was dissected and completely removed. There was no infiltrative margin or tumor necrosis. Microscopically, alternating hypercellular and hypocellular areas with thickened keloid-like collagen fibers were seen. There were no mitoses or cellular atypia. Immunohistochemical staining revealed a strong positive reaction for CD34, but negative staining for actin M851, S100, and AE1/AE3. Ki67 showed only 1% positivity. There was no recurrence of the tumor at a 3-year post-surgical follow-up.
3. Discussion SFTs are uncommon, benign, and slowly progressing spindlecell tumors. They were originally described on the mesothelial surfaces of the pleura. In line with the hypothesized origin of the tumor from mesenchymal cells with fibroblastic proliferation, it has been called a “localized mesothelioma.”1 However, the histogenesis of SFT is still controversial. Recently, this tumor has been described in extrapleural sites such as the upper airway tract, nasal and paranasal sinuses, parotid and salivary glands, thyroid, lung, mediastinum, pericardium, peritoneum, liver, spine, soft tissue, and orbit.1 Orbital SFTs can affect any orbital space. Lesions arising from lacrimal gland fossa, lacrimal sacs, conjunctivae, and sclerae have also been reported.6e9
122
W.-M. Cheang et al. / Taiwan Journal of Ophthalmology 3 (2013) 120e122
Fig. 2. Computed tomography shows a well-enhanced lesion over the inferior aspect of the left orbital cavity (arrow).
Only 48 cases of orbital SFT have been published in the literature.1,2 Orbital SFTs affect a wide age range (9e76 years) of patients, predominating in middle-aged adults. There is no obvious predilection by sex. The most common clinical sign is unilateral painless proptosis with an insidious onset over several months to years (range: 6e84 months). In our study, both cases were middle-aged women who presented with a progressive, painless, unilateral orbital mass. In our cases, the orbital SFTs were shown as well-circumscribed, contrast-enhanced masses on CT imaging. The radiological findings of orbital SFT have been described by Kim et al.3 Orbital SFTs appear as well-circumscribed masses with moderate to intense enhancement and mostly without characteristics of bony erosion on CT scanning. On MRI scans, they demonstrate T1-weighted signal isointensity and T2-weighted hypointensity. However, the radiologic features of orbital SFTs are rather nonspecific. It is difficult to differentiate them from highly vascular lesions such as hemangiomas, fibrous histiocytomas, neurofibromas, meningiomas, and schwannomas. The first orbital SFT was independently reported by Westra et al4 and Dorfman et al5 in 1994. They described the classic histopathologic features and immunohistochemical characteristics of SFTs, with alternating hypercellular and hypocellular areas of spindle cells against a background of thick collagen bundles, and a hemangiopericytoma-like pattern of vascularity.4,5,10 Moreover, CD34 is believed to be the most important diagnostic marker for SFT. SFT shows a strong and diffuse immunopositivity for CD34 (in 79e100% of cases), vimentin, and bcl-2, and immunonegativity for keratin, cytokeratin, epithelial membrane antigen, S100, smooth muscle actin, and desmin on immunohistochemical staining.4,11e13 Both of our cases showed a low Ki67 proliferative indexdless than 5% and only 1%, respectively. The Ki-67 index usually reacts in 0e2% of spindle-cell nuclei in benign SFT. In malignant cases, the percentage of positively staining nuclei can be up to 40%.14 The mainstay of treatment of orbital SFTs is surgical resection. Generally, orbital SFTs represent a benign disease, and most cases
have been treated by local excision. Both of our patients were free of recurrence for several years after complete resection of their tumor. However, local recurrence has been reported in nine cases in the literature.1,2 These were mainly related to incomplete initial excision and the increased mitotic activity of the tumor. Only one case of malignant transformation with 8 years of follow-up has been reported to date.15 The aggressive histologic pattern of the tumor can include abnormal mitotic figures, cellular pleomorphism, and giant tumor cells.16e18 In conclusion, SFTs are rare but should be included in the differential diagnosis of orbital tumors in a patient who presents with a well-circumscribed and contrast-enhanced mass. The histologic characteristics and immunohistochemical markers, including CD34 positivity, are important diagnostic tools in diagnosing an SFT. Complete surgical excision with careful postoperative follow-up is the mainstay of treatment. References 1. Bernardini FP, de Conciliis C, Schneider S, Kersten RC, Kulwin DR. Solitary fibrous tumor of the orbit. Is it Rare? Report of a case series and review of the literature. Ophthalmology 2003;110:1442e8. 2. Subramanian N, Mohan ER, Mahesh L, Biswas J, Rao NA. Solitary fibrous tumor of the orbit: a clinicopathologic study of six cases with review of the literature. Surv Ophthalmol 2003;48:544e54. 3. Kim HJ, Kim HJ, Kim YD, Yim YJ, Kim ST, Jeon P, et al. Solitary fibrous tumor of the orbit: CT and MR imaging findings. Am J Neuroradiol 2008;29:857e62. 4. Westra WH, Gerald W, Rosai J. Solitary fibrous tumor. Consistent CD34 immunoreactivity and occurrence in the orbit. Am J Surg Pathol 1994;18:992e8. 5. Dorfman DM, To K, Dickersin GR, Rosenberg AE, Pilch BZ. Solitary fibrous of the orbit. Am J Surg Pathol 1994;18:281e7. 6. Scott IU, Tanenbaum M, Rubin D, Lores E. Solitary fibrous tumor of the lacrimal gland fossa. Ophthalmology 1996;103:1613e8. 7. Woo KI, Suh YL, Kim YD. Solitary fibrous tumor of the lacrimal sac. Ophthal Plast Reconstr Surg 1999;15:450e3. 8. Pe’er J, Maly A, Deckel Y, Frenkel S. Solitary fibrous tumor of the conjunctiva. Arch Ophthalmol 2007;125:423e6. 9. Su GW, Perez N, Simons KB, Harris GJ. Solitary fibrous tumor of the sclera. Arch Ophthalmol 2007;125:1572e4. 10. Arturi L, Bollero D, Pucci A, Ferrero R, Hamedani M. Solitary fibrous tumor of the orbit: clinical and histological evidence. Eur J Plast Surg 2004;26:419e21. 11. Suster S, Fisher C, Moran CA. Expression of bcl-2 oncoprotein in benign and malignant spindle cell tumors of soft tissue, skin, serosal surfaces, and gastrointestinal tract. Am J Surg Pathol 1998;22:863e72. 12. Paal E, Miettinen M. Retroperitoneal leiomyomas: a clinicopathologic and immunohistochemical study of 56 cases with a comparison to retroperitoneal leiomyosarcomas. Am J Surg Pathol 2001;25:1355e63. 13. Miettinen M, Shekitka KM, Sobin LH. Schwannomas in the colon and rectum: a clinicopathologic and immunohistochemical study of 20 cases. Am J Surg Pathol 2001;25:846e55. 14. Hanau CA, Miettinen M. Solitary fibrous tumor: histological and immunohistochemical spectrum of benign and malignant variants presenting at different sites. Hum Pathol 1995;26:440e9. 15. Carrera M, Prat J, Quintana M. Malignant solitary fibrous tumor of the orbit: report of a case with 8 years follow up. Eye 2001;15:102e4. 16. Heathcote JG. Pathology update: solitary fibrous tumor of the orbit. Can J Ophthalmol 1997;32:432e5. 17. Alexandrakis G, Johnson TE. Recurrent orbital solitary fibrous tumor in a 14year-old girl. Am J Ophthalmol 2000;130:373e6. 18. McElvanney AM, Noble JL, O’Donovan DG, Bonshek RE, Banerjee SS. Solitary fibrous tumour: an atypical presentation within the orbit. Eye 1996;10(Pt 3): 396e9.
Contents lists available at SciVerse ScienceDirect
Taiwan Journal of Ophthalmology journal homepage: www.e-tjo.com
Case report
Orbital solitary fibrous tumor: A report of two cases Wai-Man Cheang a, Li-Chen Wei a, *, John Wang b, Hin-Yeung Tsai a a b
Department of Ophthalmology, Taichung Veterans General Hospital, Taichung, Taiwan, ROC Department of Pathology, Taichung Veterans General Hospital, Taichung, Taiwan, ROC
a r t i c l e i n f o
a b s t r a c t
Article history: Received 8 January 2013 Received in revised form 23 April 2013 Accepted 13 May 2013 Available online 25 June 2013
Solitary fibrous tumor (SFT) is a rare spindle-cell neoplasm that can be found in the orbit. Here, we report two cases affected by orbital SFT. Both patients were female, aged 52 years and 59 years, respectively, and had experienced a painless unilateral orbital lesion. Computed tomography (CT) imaging revealed a wellcircumscribed and contrast-enhanced soft tissue mass simultaneously. The tumors were located in the laterotemporal extraconal space of the right orbit and the inferior portion of the left orbit, respectively. Both patients underwent complete resection of their tumors. The histological findings showed alternating hypercellular and hypocellular areas composed of bland spindle cells with a fibrous stroma. The strong immunoreactivity for CD34 supported the diagnosis of orbital SFT. There was no recurrence at the 2-year and 3-year follow-up visits, respectively. SFTs should be considered in the differential diagnosis of an orbital tumor. The combination of a CT scan, histologic findings, and immunohistochemical staining will provide an accurate diagnosis. En bloc excision of the tumor is the mainstay of treatment in order to avoid recurrence. Copyright Ó 2013, The Ophthalmologic Society of Taiwan. Published by Elsevier Taiwan LLC. All rights reserved.
Keywords: immunohistochemical staining orbital solitary fibrous tumor surgery
1. Introduction Solitary fibrous tumors (SFTs) arise from mesenchymal cells or fibroblasts. They usually present in the pleura, but recently a few cases involving the orbit have been described.1,2 Patients with an orbital SFT may present with unilateral, painless, slowly progressive proptosis or a palpable mass in the periocular area. Computed tomography (CT) scanning and magnetic resonance imaging (MRI) reveal a well-circumscribed, contrast-enhanced soft tissue mass.3 Histological examination and positive CD34 immunoreactivity are useful in discriminating SFTs from other tumors.4,5 Here, we report two cases of orbital SFT. 2. Case reports 2.1. Case 1 A 52-year-old woman developed gradual proptosis of the right eye over several months. On ophthalmic examination, her visual acuity was 6/6.7 in the right eye. There was upward and lateral
limitation of right ocular movement. The lesion caused an inferior displacement of the eyeball and exophthalmos (Fig. 1A). Hertel exophthalmometry gave readings of 16.5 mm for the right eye and 13 mm for the left eye. CT scans revealed a contrast-enhanced solitary mass located in the lateral extraconal space of the right orbital cavity without bony erosion (Fig. 1B). A lateral orbitotomy was performed. The mass was dissected and excised completely (Fig. 1C). The bone fragment was then replaced and secured with 3-0 nylon through pre-drilled holes. In its gross dimensions, the lesion was a 3.8 cm 3 cm 1.5 cm, thin, encapsulated, and well-circumscribed tumor. Microscopically, it revealed coexistent hypocellular and hypercellular areas separated by fibrous stroma (Fig. 1D and E). The hypercellular areas were composed of bland spindle cells with a storiform pattern. No mitotic activity or atypia cells were found. The subsequent immunohistochemical staining revealed CD34 positivity (Fig. 1F), Ki-67 positivity of less than 5%, and S100 negativity. The patient was free of recurrence at a 2-year post-surgical follow-up. 2.2. Case 2
* Corresponding author. Department of Ophthalmology, Taichung Veterans General Hospital, Number 160, Section 3, Chung-Kang Road, Taichung City 40705, Taiwan, ROC. E-mail address: [email protected] (L.-C. Wei).
A 59-year-old woman had developed a slowly progressing, palpable, painless mass over the infraorbital area of her left eye over the previous 3 years. Her visual acuity was 6/6.7 for the left eye.
2211-5056/$ e see front matter Copyright Ó 2013, The Ophthalmologic Society of Taiwan. Published by Elsevier Taiwan LLC. All rights reserved. http://dx.doi.org/10.1016/j.tjo.2013.05.004
W.-M. Cheang et al. / Taiwan Journal of Ophthalmology 3 (2013) 120e122
121
Fig. 1. (A) Upper eyelid swelling, proptosis, and medial inferior deviation of the globe is noted in the patient’s right eye. (B) Coronal CT scan reveals a contrast-enhanced mass (*) next to the lacrimal gland (arrow) in the lateral extraconal space of the right orbit, causing downward displacement of the globe. (C) The 3.5 cm mass is dissected and removed completely. (D) Photomicrograph showing diffuse spindle cells and collagen deposition (magnification 200). (E) Histology reveals the deposition of abundant collagen fibers and hypercellular (arrowhead) and hypocellular (asterisk) areas (magnification 100). (F) Immunohistochemical staining shows positivity for CD34 (magnification 200).
Findings relating to extraocular movement, pupillary examination, and Hertel exophthalmometry were unremarkable. CT scans revealed a well-enhanced orbital mass located at the left inferior aspect of the orbit (Fig. 2). The patient underwent anterior orbitotomy via the lower eyelid. A 2 cm 1.5 cm 1 cm, tan-colored, wellcircumscribed tumor was dissected and completely removed. There was no infiltrative margin or tumor necrosis. Microscopically, alternating hypercellular and hypocellular areas with thickened keloid-like collagen fibers were seen. There were no mitoses or cellular atypia. Immunohistochemical staining revealed a strong positive reaction for CD34, but negative staining for actin M851, S100, and AE1/AE3. Ki67 showed only 1% positivity. There was no recurrence of the tumor at a 3-year post-surgical follow-up.
3. Discussion SFTs are uncommon, benign, and slowly progressing spindlecell tumors. They were originally described on the mesothelial surfaces of the pleura. In line with the hypothesized origin of the tumor from mesenchymal cells with fibroblastic proliferation, it has been called a “localized mesothelioma.”1 However, the histogenesis of SFT is still controversial. Recently, this tumor has been described in extrapleural sites such as the upper airway tract, nasal and paranasal sinuses, parotid and salivary glands, thyroid, lung, mediastinum, pericardium, peritoneum, liver, spine, soft tissue, and orbit.1 Orbital SFTs can affect any orbital space. Lesions arising from lacrimal gland fossa, lacrimal sacs, conjunctivae, and sclerae have also been reported.6e9
122
W.-M. Cheang et al. / Taiwan Journal of Ophthalmology 3 (2013) 120e122
Fig. 2. Computed tomography shows a well-enhanced lesion over the inferior aspect of the left orbital cavity (arrow).
Only 48 cases of orbital SFT have been published in the literature.1,2 Orbital SFTs affect a wide age range (9e76 years) of patients, predominating in middle-aged adults. There is no obvious predilection by sex. The most common clinical sign is unilateral painless proptosis with an insidious onset over several months to years (range: 6e84 months). In our study, both cases were middle-aged women who presented with a progressive, painless, unilateral orbital mass. In our cases, the orbital SFTs were shown as well-circumscribed, contrast-enhanced masses on CT imaging. The radiological findings of orbital SFT have been described by Kim et al.3 Orbital SFTs appear as well-circumscribed masses with moderate to intense enhancement and mostly without characteristics of bony erosion on CT scanning. On MRI scans, they demonstrate T1-weighted signal isointensity and T2-weighted hypointensity. However, the radiologic features of orbital SFTs are rather nonspecific. It is difficult to differentiate them from highly vascular lesions such as hemangiomas, fibrous histiocytomas, neurofibromas, meningiomas, and schwannomas. The first orbital SFT was independently reported by Westra et al4 and Dorfman et al5 in 1994. They described the classic histopathologic features and immunohistochemical characteristics of SFTs, with alternating hypercellular and hypocellular areas of spindle cells against a background of thick collagen bundles, and a hemangiopericytoma-like pattern of vascularity.4,5,10 Moreover, CD34 is believed to be the most important diagnostic marker for SFT. SFT shows a strong and diffuse immunopositivity for CD34 (in 79e100% of cases), vimentin, and bcl-2, and immunonegativity for keratin, cytokeratin, epithelial membrane antigen, S100, smooth muscle actin, and desmin on immunohistochemical staining.4,11e13 Both of our cases showed a low Ki67 proliferative indexdless than 5% and only 1%, respectively. The Ki-67 index usually reacts in 0e2% of spindle-cell nuclei in benign SFT. In malignant cases, the percentage of positively staining nuclei can be up to 40%.14 The mainstay of treatment of orbital SFTs is surgical resection. Generally, orbital SFTs represent a benign disease, and most cases
have been treated by local excision. Both of our patients were free of recurrence for several years after complete resection of their tumor. However, local recurrence has been reported in nine cases in the literature.1,2 These were mainly related to incomplete initial excision and the increased mitotic activity of the tumor. Only one case of malignant transformation with 8 years of follow-up has been reported to date.15 The aggressive histologic pattern of the tumor can include abnormal mitotic figures, cellular pleomorphism, and giant tumor cells.16e18 In conclusion, SFTs are rare but should be included in the differential diagnosis of orbital tumors in a patient who presents with a well-circumscribed and contrast-enhanced mass. The histologic characteristics and immunohistochemical markers, including CD34 positivity, are important diagnostic tools in diagnosing an SFT. Complete surgical excision with careful postoperative follow-up is the mainstay of treatment. References 1. Bernardini FP, de Conciliis C, Schneider S, Kersten RC, Kulwin DR. Solitary fibrous tumor of the orbit. Is it Rare? Report of a case series and review of the literature. Ophthalmology 2003;110:1442e8. 2. Subramanian N, Mohan ER, Mahesh L, Biswas J, Rao NA. Solitary fibrous tumor of the orbit: a clinicopathologic study of six cases with review of the literature. Surv Ophthalmol 2003;48:544e54. 3. Kim HJ, Kim HJ, Kim YD, Yim YJ, Kim ST, Jeon P, et al. Solitary fibrous tumor of the orbit: CT and MR imaging findings. Am J Neuroradiol 2008;29:857e62. 4. Westra WH, Gerald W, Rosai J. Solitary fibrous tumor. Consistent CD34 immunoreactivity and occurrence in the orbit. Am J Surg Pathol 1994;18:992e8. 5. Dorfman DM, To K, Dickersin GR, Rosenberg AE, Pilch BZ. Solitary fibrous of the orbit. Am J Surg Pathol 1994;18:281e7. 6. Scott IU, Tanenbaum M, Rubin D, Lores E. Solitary fibrous tumor of the lacrimal gland fossa. Ophthalmology 1996;103:1613e8. 7. Woo KI, Suh YL, Kim YD. Solitary fibrous tumor of the lacrimal sac. Ophthal Plast Reconstr Surg 1999;15:450e3. 8. Pe’er J, Maly A, Deckel Y, Frenkel S. Solitary fibrous tumor of the conjunctiva. Arch Ophthalmol 2007;125:423e6. 9. Su GW, Perez N, Simons KB, Harris GJ. Solitary fibrous tumor of the sclera. Arch Ophthalmol 2007;125:1572e4. 10. Arturi L, Bollero D, Pucci A, Ferrero R, Hamedani M. Solitary fibrous tumor of the orbit: clinical and histological evidence. Eur J Plast Surg 2004;26:419e21. 11. Suster S, Fisher C, Moran CA. Expression of bcl-2 oncoprotein in benign and malignant spindle cell tumors of soft tissue, skin, serosal surfaces, and gastrointestinal tract. Am J Surg Pathol 1998;22:863e72. 12. Paal E, Miettinen M. Retroperitoneal leiomyomas: a clinicopathologic and immunohistochemical study of 56 cases with a comparison to retroperitoneal leiomyosarcomas. Am J Surg Pathol 2001;25:1355e63. 13. Miettinen M, Shekitka KM, Sobin LH. Schwannomas in the colon and rectum: a clinicopathologic and immunohistochemical study of 20 cases. Am J Surg Pathol 2001;25:846e55. 14. Hanau CA, Miettinen M. Solitary fibrous tumor: histological and immunohistochemical spectrum of benign and malignant variants presenting at different sites. Hum Pathol 1995;26:440e9. 15. Carrera M, Prat J, Quintana M. Malignant solitary fibrous tumor of the orbit: report of a case with 8 years follow up. Eye 2001;15:102e4. 16. Heathcote JG. Pathology update: solitary fibrous tumor of the orbit. Can J Ophthalmol 1997;32:432e5. 17. Alexandrakis G, Johnson TE. Recurrent orbital solitary fibrous tumor in a 14year-old girl. Am J Ophthalmol 2000;130:373e6. 18. McElvanney AM, Noble JL, O’Donovan DG, Bonshek RE, Banerjee SS. Solitary fibrous tumour: an atypical presentation within the orbit. Eye 1996;10(Pt 3): 396e9.