Corneal stromal invasive squamous cell carcinoma: a retrospective morphological description in 10 horses.

This research article focuses on the morphological description of corneal stromal invasive squamous cell carcinoma (CSI-SCC) in horses, a condition that can be misdiagnosed as chronic stromal keratitis due to the unique intrastromal tumor growth pattern observed with it. The study reveals that a deep biopsy is necessary for proper diagnosis of the condition.

Study Design and Methodology

• The study revolves around the examination of 87 cases of squamous cell carcinoma (SCC) that were part of the Comparative Ocular Pathology Laboratory of Wisconsin database.
• From these 87 cases, 10 instances of corneal stromal invasive squamous cell carcinoma were further analyzed to understand the pathomorphological features of the condition.
• Various horses breeds were included in the study, mainly Quarter horses, Appaloosas, American Paint, Pinto, and Thoroughbred horses.
• The investigators used diverse staining techniques, such as H&E, periodic acid-Schiff stain, and Verhoeff’s elastic stain, to understand the structure and form of the examined tumors.

Results

• The average age of the horses at the time of removal of the affected eye or cornea (enucleation or keratectomy) was around 16.7 years.
• Diagnosis varied among the examined horses: half of the cases had been previously identified as chronic stromal keratitis, three cases had a diagnosis of SCC, while one case was recognized as stromal mass and one as invasive SCC.
• In some cases, horses underwent keratectomy before enucleation, with two out of three also undergoing further treatment using laser or cryotherapy.
• Tumor infiltration was reported in the anterior-mid stroma in most cases, while fewer cases showed infiltration in the mid-deep stroma.
• Surprisingly, the most of the cases showed no contact between the CSI-SCC and the anterior epithelium, and the epithelium was often observed to be intact and normal. Also, the limbus (border area between the cornea and the sclera) was unpigmented in the majority of the specimens.
• A mild to moderate inflammation of lymphoplasmacytic cells was noted around the cancerous growths.
• Lastly, solar elastosis (a condition caused by extensive exposure to the sun and characterized by degenerative changes in the skin’s elastic tissues) was observed in some samples.

Conclusion

• The researchers concluded that CSI-SCC in horses exhibits a unique pattern of tumor growth within the stroma, featuring a smooth, intact corneal epithelium.
• This distinct pattern leads to underestimation and misdiagnosis of the condition as chronic active stromal keratitis.
• The authors advocate for the use of a deep biopsy as a more reliable method of diagnosing the condition accurately.