Multiple follicular cysts of the ear canal in a dog

Histologic features of hair follicle neoplasms and cysts in dogs and cats: a diagnostic guide

Hair follicle neoplasms occur in many different species, including humans. In domestic animals, they are most common in dogs. Most hair follicle tumors are benign, but malignant neoplasms can also occur. To diagnose hair follicle neoplasms, a thorough knowledge of follicular anatomy is important, given that follicular tumors are classified according to the differentiation pattern seen in the corresponding part of the normal hair follicle. This review focuses on the key diagnostic features of hair follicle tumors and follicular cysts in dogs and cats.

Multiple follicular cysts in four alpacas (Vicugna pacos)

Follicular cysts are non-neoplastic skin lesions lined by follicular epithelium. The pathogenesis of these lesions is unclear. Multiple follicular cysts occur sporadically in dogs, horses and humans and are common in sheep. Here we report multiple follicular cysts in four aged alpacas (Vicugna pacos). Based on their histological features, they are most consistent with hybrid cysts. This is the first report of multiple follicular cysts in alpacas.