## 3 Tumor Staging and Histological Findings  
The clinical and pathologic staging guidelines of the seventh edition of the American Joint Committee on Cancer-Union for International Cancer Control (AJCC-UICC) TNM system are derived from a multicenter retrospective evaluation of more than 8000 patients and document tumor size and extension, the presence of secondary glaucoma, regional lymph nodes and distant metastasis: T0--No evidence of primary tumor; T1--Tumor limited to the iris; T1a--Tumor limited to the iris (not more than three clock hours in size); T1b--Tumor limited to the iris (more than three clock hours in size); T1c--Tumor limited to the iris with secondary glaucoma; T2--Tumor confluent with or extending into the ciliary body, choroid or both; T2a--Tumor confluent with or extending into the ciliary body, choroid or both with secondary glaucoma; T3--Tumor confluent with or extending into the ciliary body, choroid or both with scleral extension; T3a--Tumor confluent with or extending into the ciliary body, choroid or both with scleral extension and secondary glaucoma; T4--Tumor with extraocular extension; T4a--Tumor with extrascaleral extension \(>\)5 mm in diameter; T4b--Tumor with extrascaleral extension \(>\)5 mm in diameter; NX--Regional lymph nodes cannot be assessed; N0--No regional lymph node metastasis; N1--Regional lymph node metastasis; MX--Distant metastasis cannot be assessed; M0--No distant metastasis; M1--Distant metastasis; M1a--Largest diameter of the largest metastasis (\(<\)3 cm); M1b--Largest diameter of the largest metastasis (\(>\)8 cm); GX--Grade cannot be assessed; G1--Spindle cell melanoma; G2--Mixed cell melanoma; and--G3 Epithelioid cell melanoma. The AJCC eighth edition classification for iris melanoma showed minimal changes compared with the seventh edition. The main differences are evident in categories T2 and T3. The more recent eighth edition differentiates category T2 with regards to invasion of the ciliary body only (T2a) and both the ciliary body and choroid (T2b). Moreover, it eliminates the T3a category because of the small number of iris melanomas that fall into this category. Categories T1 and T4 remained unchanged [28]. When there is a clinical suspicion of melanoma, fine-needle aspiration biopsy (FNAB) is recommended [10]. The most frequently used needles for ophthalmic FNAB are 25 to 30 gauge, because the likelihood of an insufficient sample increases with needles below 22 gauge and above 30 gauge [10]. In order to decrease the risk of a negative biopsy, [PERSON] et al. recommended bending the needle tip to 90 degrees and entering the tumor tangentially rather than radially [10; 29]. The sample is then retrieved using intraocular forceps that are specially designed for histological and immunohistochemical typing. Complications from iris biopsy such as persistent hyphema, prolonged hypotony, lens damage or endophthalmitis have been reported in less than 1% of cases [10]. Adequate results can be achieved in collaboration with an experienced surgeon and cytopathologist [10]. Iris melanomas usually have a blander morphology than choroidal and ciliary body melanomas and vary from completely amelonic to densely pigmented. There are three histologic types of iris melanomas: spindle cell, mixed cell and epithelhelioid cell melanomas. Morphologically, spindle cells or epithelhelioid cells may be observed. The first have nuclei with linear interdigitation related to a chromatin strip, small nucleoli (spindle B cells) or with no evidence of nucleoli (spindle A cells). Epithelioid cells are larger, polygonal cells with an abundant, glassy cytoplasm, distinct cell border and a large, round nucleus with marginated coarse chromatin [30]. Mixed cell type melanomas have a variable number of both cell types. The mitotic activity of iris melanomas is usually low and varies from 1 to 3 mitoses per 20 high-power fields. Iris melanomas, as choroidal and ciliary body melanomas, are positive for S100 protein, HMB45 antigen, and melan-A [30].