Spontaneous squamous cell carcinoma in the cloacal scent gland from a Mexican Black Kingsnake

Michelle Yee, Heindrich Snyman

The Links Road Animal & Bird Clinic, Toronto, ON (Yee); Animal Health Laboratory, University of Guelph, Guelph, ON (Snyman)

AHL Newsletter, 2020;24(1):13-14.

A male Mexican Black Kingsnake (Lampropeltis getula nigrita) presented with re-occurring swelling and inflammation around the cloacal and scent gland region. One month previously, the snake was treated with ceftazadime for a suspected scent gland infection. The infection appeared to respond to antibiotic therapy, but the swelling never completely resolved. On representation, the scent gland region was severely inflamed with thick purulent discharge (Fig. 1A). Additionally, two new small firm subcutaneous masses had formed on the snake’s left lateral region, cranial to the cloaca. Upon surgical exploration of the scent gland abscess, multiple abnormal, distinct circular soft tissue masses were identified underlying the purulent discharge. These masses seemed to coalesce caudally, appeared to invade the surrounding musculature around the spine and effaced the left hemipene cranially. Samples for both histopathology and aerobic bacterial culture were obtained.

The histopathology results revealed squamous cell carcinoma (SCC) with local tissue invasion and associated scirrhous response (Fig. 1B-1D).  Bacterial culture grew Proteus mirabilis. It is believed that the SCC originated from the left scent gland with a concomitant secondary bacterial infection. Additionally, it is suspected that masses located cranial to the initial site were secondary abscesses rather than regionalized tumor metastasis. Seven days post-operatively, the primary scent gland site had dehisced while the secondary sites remained intact.

Commonly affected anatomic sites for SCC in snakes include the oral cavity, cloacal skin, cloacal scent glands, and hemipenes. Similar to other species, SCC is usually locally aggressive and destructive. Clinical deterioration due to local disease usually occurs before metastasis to internal organ which is uncommon. Recent reports described the development of oropharyngeal SCC in snakes associated with infection by a novel alphaherpesvirus, Opheodrys herpesvirus 1. Additionally, oral SCC often occurs with concurrent stomatitis, and chronic inflammation may play a role in neoplastic transformation. This highlights the importance of further work up and histopathology for masses noted around a snake’s oral and cloacal regions, especially if an initial abscess is suspected.  AHL

References

1. Ossiboff RJ. Serpentes. In: Pathology of Wildlife and Zoo Animals. Terio KA et al, eds. Elsevier 2018:904-908. Anderson ET et al. Squamous cell carcinoma with vascular invasion in a diamondback rattlesnake (Crotalus adamanteus). J Zoo Wildl Med 2010;41(4):745-748.

2. Lovstad, JN, Ossiboff, RJ, Kinsel, MJ. Novel herpesvirus associated with oropharyngeal squamous cell carcinoma in smooth green snakes (Opheodrys vernalis). Vet Pathol 2019;56(4):630-635.