11 yo Female DSH

SIGNALMENT: 11-year-old, female spayed, Domestic Short Hair, Feline.

SOURCE/HISTORY: Small, intradermal mass, slow growing, raised, pink, smooth with discharge seen at times. Located on the top of the head. Does scratch at it.

MICROSCOPIC DESCRIPTION: Haired skin: The dermis is expanded by a well demarcated and expansile mass comprised of a flask shaped invagination lined by scalloped, hyperplastic epithelium contiguous with the epidermis and open to the surface. Centrally there is abundant orderly accumulation of laminated keratin with protrusion above the skin surface (horn formation).

Figure 1. Low magnification (5X). This section of haired skin demonstrates a well-demarcated, expansile, flask-shaped, endophytic, cystic mass. The wall of the cyst is contiguous with the epidermis forming a pore through which abundant luminal cornified debris forms a protruding horn.
Figure 2. Higher magnification (50X). The cyst wall is composed of relatively regularly scalloped, hyperplastic epithelium producing marked luminal cornified debris. There is mild compression of the adjacent dermis and adnexa with no evidence of infiltrative growth by the hyperplastic cyst lining.
Click here for the IDEXX Pathology Report on this case.

MICROSCOPIC INTERPRETATION:

Haired skin: Benign dilated pore (of Winer), completely excised

COMMENTS: Dilated pore is an uncommon, benign lesion that is more common in cats than dogs. Lesions are most frequently located in the skin of the head or neck. They present as a solitary, firm mass, less than 1 cm in diameter with a central dome-shaped protrusion of dense keratin. Rupture or trauma can cause secondary dermatitis. The cause is unknown. In human patients, the counterpart is known as “dilated pore of Winer”. Excision should be curative.

PATHOLOGIST: Jeremy Tobias, DVM Diplomate, American College of Veterinary Pathologists

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