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S. Vangveeravong, X. Chen, D. Majumdar, A.J. Maniotis, R. Folberg, J. Pe'er; Extravascular Matrix (Looping PAS-Positive) Patterns in Retinoblastoma . Invest. Ophthalmol. Vis. Sci. 2003;44(13):1572.
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Purpose: There are no lymphatic channels within the eye. Therefore, retinoblastoma, like uveal melanoma, spreads exclusively by a hematogenous route unless the conjunctiva is involved by extraocular extension. In uveal melanoma, the looping matrix patterns are not blood vessels, but they connect to blood vessels. These extravascular matrix patterns have been shown to conduct fluid in vitro and in vivo. Moreover, the presence of these patterns histologically is associated with death from metastatic uveal melanoma, consistent with observations from in vitro studies associating pattern formation by the tumor cell to highly invasive melanoma cells. Looping extravascular matrix patterns are not restricted to uveal melanoma and are found in cutaneous melanoma, ovarian carcinoma, and inflammatory breast cancer. This study was designed to investigate the possibility that looping extravascular matrix patterns might be present in invasive retinoblastoma. Methods: All retinoblastomas accessioned by the Ophthalmic Pathology Laboratory at the Hadassah University Hospital between 1990 and 2001 (76) were available for histological study. Of these, 28 cases originated from a Hadassah outreach clinics in Kenya or Malawi. Serial sections were stained with hematoxylin-eosin and with periodic acid-Schiff (PAS) without counterstaining, a method used to detect extravascular matrix patterns in uveal melanoma with high reproducibility. Results: Each eye contained retinoblastoma within the retina and/or vitreous: invasion into the retrolaminar compartment of the optic nerve was detected in 18/73 cases (25%; in 3 cases, we could not assess optic nerve invasion), choroidal invasion in 31/76 cases (49%), and extraocular extension in 17/76 cases (22%). PAS-positive patterns were detected in the intraocular component of 5/76 eyes (7%) and were not seen in any of the zones of retrolaminar optic nerve invasion. In eyes that featured choroidal invasion or extraocular extension, extravascular matrix patterns were present in 22/31 (71%) and 12/17 (71%) of the invasive tumor components respectively. Conclusions: The expression of extravascular matrix patterns in retinoblastoma appears to reflect the presence of an invasive retinoblastoma phenotype. However, the formation of these patterns generally requires a permissive microenvironment because these patterns are not seen in optic nerve invasion but are identified in the collagen-rich environment of the choroid and within orbital soft tissue.
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