Intra-abdominal mass aspirate from an alopecic dog

An 11-year-old female Yorkshire terrier was presented to the University of Minnesota Veterinary Medical Center for evaluation of a palpable intra-abdominal mass and alopecia. Abdominal ultrasonography revealed a large, complex, cavitary mass in the left caudal region of the abdomen. A fine needle aspirate of the mass was collected. A population of markedly pleomorphic, large, round to polygonal cells were found singly and in small noncohesive aggregates. The cells contained scant, clear to blue-gray cytoplasm, large, round to oval nuclei, and distinctly stippled to reticular chromatin. Cytologic findings were consistent with a tumor of ovarian origin, with a primary differential diagnosis of germ cell tumor. Hormonal analysis of serum revealed a marked increase in 14-OH-progesterone concentration (2.71 ng/mL, reference interval 0.05-0.69 ng/mL). Ovariohysterectomy was performed, and the mass was found to be in the area of the left ovary. Histologic evaluation of the reproductive tract confirmed a diagnosis of left ovarian dysgerminoma. Based on immunohistochemical stains, the tumor was negative for c-kit (CD117c) and single cells were positive for neuron-specific enolase. A right ovarian cyst and squamous metaplasia of the right uterine horn also were diagnosed. The cyst was presumed to be the source of 14-OH-progesterone, which likely resulted in the squamous metaplasia and dermatopathy. Three months after surgery, the progesterone concentration had returned to normal and the alopecia had nearly resolved. Dysgerminomas in dogs are reported rarely, but have a distinctive, recognizable, cytologic appearance and should be included in the differential diagnosis of an intra-abdominal mass in a reproductively intact female dog.