Unilateral accessory tragi in a cat

Area of Science:

• Veterinary Pathology
• Comparative Anatomy
• Congenital Malformations

Background:

• Accessory tragus is a congenital malformation of the external ear, arising from the first pharyngeal arch.
• In humans, it can be linked to congenital syndromes, often with autosomal dominant inheritance.
• Previous veterinary reports are scarce, with only one documented case in a dog.

Purpose of the Study:

• To report the first documented cases of accessory tragi in a feline patient.
• To provide detailed histopathological descriptions of this rare congenital anomaly in cats.
• To highlight diagnostic considerations for pathologists encountering this lesion.

Main Methods:

• Clinical observation of three cutaneous exophytic lesions in the preauricular region of a cat.
• Histologic examination of two submitted lesions.
• Microscopic analysis of tissue composition, including epidermal structure, collagenous stroma, adnexal structures, and cartilage.

Main Results:

• Two lesions diagnosed as accessory tragi were identified in a 2.5-year-old European shorthair cat.
• Histologically, lesions showed a collagenous core with adnexal structures and epidermal folds; one contained elastic cartilage.
• The epidermis was of normal thickness and slightly hyperpigmented.

Conclusions:

• Accessory tragus is reported for the first time in cats, expanding its known occurrence in veterinary medicine.
• The histopathological findings provide a basis for diagnosing this rare condition in felines.
• Accurate diagnosis may be challenging, particularly without cartilage or with unknown sample location.