Pathology of the Uveal Tract: Neoplasms

Abstract

Neoplasms of the uveal tract are relatively uncommon overall, but the uveal tract is the most common intraocular tissue affected by neoplasia. In this chapter, we discuss the pathology of the most commonly encountered neoplasms and tumor-like conditions occurring in the uveal tract. Secondary neoplasms are more common than primary neoplasms, and the most frequent malignant neoplasm of the uveal tract in adults is metastatic carcinoma. Melanocytic proliferations, including both benign nevi and malignant melanoma, are the most common primary intraocular neoplasms. Melanomas of the ciliary body and choroid are life-threatening tumors, while iris melanomas rarely metastasize or cause death. The main histopathologic features correlated with poor prognosis in ciliochoroidal melanoma are the following: epithelioid cell type, tumor size, and extrascleral tumor extension. GNAQ/GNA11 gene mutations, which are present in virtually all uveal melanomas, are not prognostically significant, are insufficient alone to induce malignant transformation, but are required to initiate tumorigenesis. The genetic findings that are prognostic of metastatic risk are: monosomy 3 and BAP1 mutations (high metastatic risk), SF3B1 mutations (intermediate metastatic risk), and EIF1AX (low metastatic risk). Gene expression profiling can group uveal melanomas into Class 1A (low metastatic risk), Class 1B (intermediate metastatic risk), and Class 2 (high metastatic risk). Medulloepithelioma is a tumor derived from the ciliary neuroepithelium that typically affects children and may be confused with retinoblastoma. The choroid may give rise to localized or diffuse hemangiomas. Diffuse types are associated with Sturge-Weber syndrome. Choroidal osteoma is a bony, choristomatous lesion of the peripapillary choroid that typically occurs in young women. Leiomyoma is a benign neoplasm of smooth muscle origin that can occur rarely in the ciliary body and may clinically mimic amelanotic melanoma. Secondary leukemic infiltration of the uveal tract is common.