Remove the info you got imprinted in your brain since the New Orleans 2023 ACVR film reading session, not all feline intra-ocular melanomas will met....

Histologic and immunohistochemical predictors of clinical behavior for feline diffuse iris melanoma

K. Tomo Wiggans, Christopher M. Reilly, Philip H. Kass, David J. Maggs

Background
Feline diffuse iris melanoma (FDIM) is a common melanocytic neoplasm that often progresses to metastasis, impacting prognosis. Despite high metastatic rates, clinical and molecular prognostic indicators for FDIM remain limited. This study aimed to identify histologic and immunohistochemical markers predictive of metastasis in cats with FDIM, using enucleated globes and follow-up data on metastatic outcomes.

Methods
This retrospective study included 47 enucleated globes from cats with FDIM collected between 1985 and 2013. Histologic features (e.g., mitotic index, invasiveness) and immunohistochemical markers (melan-A, PNL2, E-cadherin, B-Raf) were assessed. Statistical associations between these parameters and metastasis were analyzed using the log-rank test and Cox proportional hazards model.

Results
Histologic Findings: Four parameters were significantly associated with increased metastatic risk:
-Extrascleral extension (P = 0.039)
-Necrosis within the tumor (P = 0.026)
-Mitotic index >7/10 high-power fields (P = 0.024)
-Choroidal invasion (P = 0.045)

Immunohistochemical Results:
-Increased intensity of melan-A and E-cadherin labeling correlated with higher metastasis rates.
-Homogeneous labeling of PNL2 was associated with reduced metastasis (P = 0.0082).
-B-Raf expression did not significantly correlate with metastasis.

Metastasis occurred in 19% of cases, with a median time to detection of 9.8 months post-enucleation.

Limitations
The study relied on retrospective data, which may limit the consistency of histologic evaluations and follow-up accuracy.
Small sample sizes for certain markers and fixation differences affected immunohistochemical results.
Only one histologic section per globe was evaluated, which may have underestimated invasiveness.

Conclusions
The study identified specific histologic (e.g., extrascleral extension, high mitotic index) and immunohistochemical markers (e.g., increased melan-A and E-cadherin intensity) as predictors of FDIM metastasis. PNL2 labeling homogeneity emerged as a potential protective indicator. These findings enhance prognostic assessment but require validation in prospective studies and evaluation in cytologic specimens to reduce reliance on enucleation.

K. Tomo Wiggans, Christopher M. Reilly, Philip H. Kass, David J. MaggsDisclaimer: The summary generated in this email was created by an AI large language model. Therefore errors may occur. Reading the article is the best way to understand the scholarly work. The figure presented here remains the property of the publisher or author and subject to the applicable copyright agreement. It is reproduced here as an educational work. If you have any questions or concerns about the work presented here, reply to this email.