Fine-Needle Aspiration Biopsy
Diagnostic intraocular fine-needle aspiration biopsy (FNAB) may be useful in distinguishing between primary uveal tumors and metastases. The procedure is performed under direct visualization through a dilated pupil, transvitreally or transsclerally (see Chapter 17, Videos 17-1 and 17-2, respectively). Iris tumors may be accessible for FNAB via sampling through the anterior chamber.
Special cytology fixatives, typically alcohol-based, are used for FNAB specimens. The cells obtained through FNAB can be processed using various cytopathologic techniques, such as a cytospin preparation, in which cells are centrifuged onto a glass slide, or when enough cells are present, they can be centrifuged and processed into a paraffin block (cell block) (Fig 3-5). A cell block allows the pathologist to employ special stains, IHC, ISH, microarray, and gene expression profiling if needed and as cellular material permits. In cases of suspected uveal melanoma, biopsy specimens can undergo genetic analysis to identify prognostic chromosomal abnormalities and gene expression profiling patterns. Intraocular FNAB has also been utilized in the diagnosis of primary intraocular lymphoma (PIOL). In cases of suspected PIOL, the biopsy specimen can undergo flow cytometric analysis, immunocytologic analysis, cytokine analysis, or molecular biological analysis (using PCR on both fixed and nonfixed material), depending on the sample volume. See also Chapters 17 and 20.
Intraocular FNAB has been postulated to increase the risk of tumor spread outside the eye, although this is controversial. In general, when properly performed, FNAB does not pose a major risk for tumor seeding. However, retinoblastoma is a notable exception, as FNAB can definitely increase the risk of local and distant tumor spread.
Some orbital surgeons have used FNAB to diagnose orbital lesions, especially optic nerve tumors and presumed metastases to the orbit. However, FNAB of an orbital mass may not adequately sample all representative areas of the tumor because it is difficult for the surgeon to make several passes at different angles through an intraorbital tumor without risking complications. Specific indications for performing intraocular or intraorbital FNAB are beyond the scope of this discussion, but some of these indications are discussed in Chapters 17 and 20 of this book. Ophthalmic FNAB should be performed with the assistance of an ophthalmic pathologist or cytopathologist experienced with these cases, because of the small amount of tissue/cells often obtained.
Figure 3-5 Fine-needle aspiration biopsy (FNAB) of a choroidal tumor. A, Cytologic liquid-based preparation displays prominent nucleoli (arrow) and some brown pigment (arrowhead) suggestive of melanoma. B, Sections from a cell block of the aspirated cells, stained with HMB-45 immunohistochemical stain using a red chromogen, is positive, confirming the diagnosis of melanoma. Notice the difference between the red chromogen color product (arrows) and the brown melanin (arrowheads).
(Courtesy of Patricia Chévez-Barrios, MD.)
Eide N, Walaas L. Fine-needle aspiration biopsy and other biopsies in suspected intraocular malignant disease: a review. Acta Ophthalmol. 2009;87(6):588–601.
McCannel TA. Fine-needle aspiration biopsy in the management of choroidal melanoma. CurrOpin Ophthalmol. 2013;24(3):262–266.
Excerpted from BCSC 2020-2021 series: Section 4 - Ophthalmic Pathology and Intraocular Tumors. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.