It is important to remember not every sublingual lesion in a cat is due to squamous cell carcinoma (SCC). Sure, if you’re playing the odds in a 10-year-old cat that presents with bloody drool, decreased appetite, and difficulty swallowing, sublingual/lingual SCC is the most likely diagnosis (Figure 1A). However, a recent case I saw reminded me to keep other differential diagnoses in mind. This article describes a few less common sublingual lesions that should be on your list of rule-outs. Ranulas If you see a smooth swelling beneath the tongue, it could be due to a ranula. From the Latin word “rana,” which means frog, a ranula is a smooth swelling underneath the tongue that looks like a frog’s underbelly. Ranulas occur from abnormal accumulation of saliva, due to damage to the duct or gland. If you lift the tongue of a cat or dog, you’ll see paired raised structures near the midline of the caudal symphysis called the caruncles. Caruncles are the duct openings for the mandibular and sublingual salivary ducts. If damage occurs to the caruncles or to the ducts that run between the glands and the caruncles, saliva may extrude and cause swelling. The swelling beneath the tongue may be bilateral or unilateral and is not typically inflamed (Figure 2A). However, if the swelling gets large enough, it may have secondary trauma from the dentition. Ranulas occasionally resolve without treatment, but often surgery is necessary to remove the mandibular and sublingual glands. A) Squamous cell carcinoma in the sublingual region of a cat. B) Eosinophilic granuloma seen in the sublingual region of a one-year-old cat. Photos courtesy Dr. John R. Lewis When we perform mandibulectomies in dogs and cats with oral tumors, it sometimes becomes necessary to transect and ligate the salivary ducts. In that case, sublingual swelling and edema from the surgery may mimic a ranula. However, these “pseudoranulas” will resolve within a few days after the surgery. Interestingly, an experimental study published in 1978 showed that damaging the duct and/or gland does not always result in an abnormal accumulation of saliva.1 It was a small sample size, but no ranulas developed in the dogs after surgical trauma to the duct and/or gland. However, I have seen at least one case of a ranula occurring postoperatively after transaction of the ducts during oncologic surgery. Eosinophilic granulomas Perhaps the classic presentation of eosinophilic granuloma is ulceration of the cat’s upper lip, also referred to as rodent ulcers. However, some manifestations of eosinophilic granuloma are not ulcerated. Swelling of the lips or the sublingual area should be on your differential list for possible eosinophilic disease. A) Ranula in a cat. B) A pseudo ranula in a cat caused by an eosinophilic granuloma. Unlike a ranula, the swelling was firm and not fluctuant. This same cat had swelling of the rostral lower lip. Diagnosis of both sites was made via histopathology of an incisional biopsy, and the lesions resolved with steroid treatment. Photos courtesy Dr. John R. Lewis Sublingual eosinophilic granulomas can mimic either squamous cell carcinomas or ranulas. Occasionally, a sublingual swelling due to eosinophilic granuloma will look very smooth, mimicking a ranula. These often occur alongside other signs of eosinophilic granuloma, such as a swollen lower lip (Figure 2B). Kirk Herrmann, DVM, DAVDC, Alex Juriga, DVM, and I recently saw a cat named Milo, a one-year-old ragdoll, with a sublingual swelling that mimicked SCC. The swelling beneath the tongue was verrucous, ulcerated, and very firm (Figure 1B). This cat also had a history of a swollen lower lip, which still appeared slightly swollen at the time of presentation for the sublingual swelling. Histopathology of the sublingual lesion revealed marked eosinophilic granulomatous glossitis with ulceration (eosinophilic granuloma). While waiting for the biopsy results, we were concerned about self-trauma from the teeth because his swelling was so severe. We started Milo on dexamethasone sodium phosphate and began a daily dose of oral prednisolone the following day at 1mg/kg/day. Within a week, the swelling decreased significantly and was nearly resolved after two weeks of steroid therapy. We recommended consulting a dermatologist to help pinpoint possible allergic causes of Milo’s eosinophilic disease. This case is a good reminder of the importance of histopathology in obtaining a definitive diagnosis. Other rarities Linear foreign bodies that wrap around the lingual frenulum can cause significant sublingual edema, erythema, and swelling of the tongue itself. Most common in young cats, linear foreign bodies can also occur in dogs. I recall a 10-year-old dog named Lily that chewed on the inner twine of a golf ball, which became wrapped around the base of the tongue (frenulum) (Figure 3). Occasionally, a large area of granulation tissue may occur in the sublingual area due to chronic irritation, such as the rough surface of a tooth created by tooth resorption. Figure 3. Linear foreign body in a 10-year-old dog (not the usual signalment). Photo courtesy Dr. John R. Lewis Next time you see a sublingual lesion in a cat, keep these possibilities on your differential list! John Lewis, VMD, DAVDC, FF-OMFS, practices veterinary dentistry and oral surgery at Veterinary Dentistry Specialists and teaches at Silo Academy Education Center, both located in Chadds Ford, Pa. References DeYoung DW, Kealy JK, Kluge IP. Attempts to produce salivary cysts in the dog. Am J Vet Res. 1978;39:185-186. Lewis, JR. What you need to know about oral eosinophilic diseases in dogs and cats. July 20, 2015. https://www.veterinarypracticenews.com/what-you-need-to-know-about-oral-eosinophilic-diseases-in-dogs-and-cats/
