Multiple eccrine poromas in the paw of a dog

A 5-year-old, spayed female boxer dog presented to the referring veterinarian with a year-long history of swelling, ulceration and pain in the pawpad of the fourth digit of the right forelimb. Histologically, the pawpad was expanded by a mass composed of small polygonal cells forming broad bands and trabeculae within the lower epidermis that often infiltrated and replaced the overlying keratinocytes and that extended into the dermis. Lobules of eccrine glands within the deep dermis occasionally had one or more eccrine ducts that were lined by neoplastic ductal epithelial cells that formed papillary projections lined by one to two layers of neoplastic cells. Approximately 1 month after amputation of the fourth digit pad, several smaller nodular masses developed in multiple digital pads and the metacarpal pad of the same paw. All of the neoplasms were histologically identical to eccrine poroma (juxtaepidermal acrospiroma), a common benign neoplasm in humans that originates from the acrosyringium and upper dermal duct of eccrine glands. To the authors' knowledge this is the first report documenting an eccrine poroma in a dog.