Cutaneous B-cell lymphoma in a Perdido Key Beach mouse (Peromyscus poliontus trissyllepsis)

The Perdido Key beach mouse (Peromyscus poliontus trissyllepsis) is an endangered mammal indigenous to the panhandle beaches of Northwest Florida. A captive 3.5-y-old female mouse was evaluated because of severe pruritus, diffuse alopecia, skin reddening, and ulcerations over the dorsum of her body. Initial skin biopsy of the affected area suggested bacterial dermatitis but was inconclusive. Despite empiric antibiotic, anthelmintic, and antihistamine treatments, she continued to decline and developed severe ulcerations over the majority of her body. Postmortem histopathologic evaluation led to a tentative diagnosis of epitheliotropic lymphoma, suggestive of a mycosis fungoides T-cell-type cutaneous lymphoma. However, immunohistochemistry results challenged this diagnosis, indicating that the lesion was actually an epidermotropic B-cell lymphoma. Spontaneous cutaneous B-cell lymphomas are rare in rodents and had not previously been reported to occur in Perdido Key beach mice. This case report provides initial evidence that the Perdido Key beach mouse is susceptible to cutaneous B-cell lymphoma.