The diagnosis of an orbital lesion usually requires analysis of tissue obtained through an orbitotomy. Appropriate handling of the tissue specimen is necessary to ensure an accurate diagnosis. Most tissue samples are placed in formalin for permanent section analysis. If a lymphoproliferative lesion is suspected, some fresh tissue should be sent for flow cytometry analysis. Frozen section evaluation may be performed at the time of surgery, but it is generally not used for definitive diagnosis of an orbital tumor. However, when the area of proposed biopsy is not obvious, frozen sections are helpful to confirm that appropriate tissue has been obtained for permanent section analysis. Frozen section analysis is also used intraoperatively to determine tumor margins and ensure complete tumor removal. Tissue removed for frozen section analysis should be placed in a dampened saline gauze and sent promptly to the frozen section laboratory.
Because of the vast array of possible unusual tumor types in the orbit, preoperative consultation with a pathologist familiar with orbital disease may be helpful to maximize the information gained from any orbital biopsy. In many cases, fresh tissue should be obtained and frozen for cell-surface-marker studies. Cell-marker studies are required in the analysis of all orbital lymphoid lesions. These studies may allow differentiation between reactive lymphoid hyperplasia and lymphoma. Such studies may also indicate the presence of estrogen receptors in cases of metastatic prostate or breast carcinoma and thus provide useful information about sensitivity to hormonal therapy. Marker studies are also helpful in the diagnosis of poorly differentiated tumors when light microscopy alone is not definitive. Although cell-marker studies have largely replaced electron microscopy in the diagnosis of undifferentiated tumors, it may nevertheless be worthwhile in these cases to preserve fresh tissue in glutaraldehyde for possible electron microscopy. In noncohesive tumors (hematologic or lymphoid), a touch preparation may permit a diagnosis.
All biopsy specimens must be treated delicately to minimize crush and cautery artifacts, which can confuse interpretation. Permanent section tissue biopsy specimens should be placed in fixatives promptly. If fine-needle aspiration biopsy is planned, a cytologist or trained technician must be available to handle the aspirate. In special cases, the biopsy can be performed under either ultrasonographic or CT control. Although a fine-bore needle occasionally yields a sufficient cell block, the specimen is usually limited to cytologic study. Larger biopsy specimens, in which light and electron microscopy can be used to evaluate histologic patterns, may permit a more conclusive diagnosis.
As the technology improves and costs decrease, genomic analysis of tumors is increasingly being performed. This modality has implications for disease prognosis and the promise of precision therapy. Discussion with the pathologist prior to surgery is recommended so that tissues can be sent in the appropriate media for optimal genetic analysis.
See BCSC Section 4, Ophthalmic Pathology and Intraocular Tumors, for a more extensive discussion of pathology.
Excerpted from BCSC 2020-2021 series: Section 10 - Glaucoma. For more information and to purchase the entire series, please visit https://www.aao.org/bcsc.