SURGICAL MANAGEMENT OF CAUDAL MANDIBULAR MASSES IN DOGS

Oral masses that develop in the back of the mouth often to go unnoticed by owners until they are substantial in size, result in noticeable changes in mouth or tongue movements, or when blood or bloody saliva is observed.  When presented with such cases, we encourage referring veterinarians to collect a biopsy of the lesion prior to referral. If we know the nature of the mass in advance, we can directly schedule curative-intent surgery with surgical margins based on the anticipated biological behavior of the tumor. If a biopsy is not performed by the referring veterinarian, we will perform an incisional biopsy including bone (if appropriate) following cone beam computed tomography (CBCT) and intraoral radiography prior to curative-intent surgical excision.

Although our prime concern is removal of the mandibular mass with tumor-free margins, quality of life and post-operative appearance are also issues that we prioritize as oral surgeons. The purpose of this article is to share how we approach such cases, and to provide our referring veterinarians with information that may help guide their initial conversations with grief-stricken pet owners. An important take-home message is that not all oral masses are neoplastic, and not all oral neoplasms are malignant. In a recent retrospective study of 338 biopsy-confirmed oral masses in dogs, lesions were grouped according to whether they were non-neoplastic, benign neoplasms, or malignant neoplasms.1 More than half of all submissions (53%) were non-neoplastic masses. Of the 160 neoplastic masses, 74% were benign and 26% were malignant. Specific to neoplastic masses in the caudal mandible, 17.8% were benign and 21.4% were malignant. In our referral practice, the most commonly seen non-neoplastic mandibular masses in dogs include focal gingival hyperplasia, osteomyelitis, and fibromatous hyperplasia of the gingival ligament, (formally called peripheral odontogenic fibromas POFs). Common benign neoplasms in the caudal mandible include canine acanthomatous ameloblastomas, other odontogenic tumors, and extramedullary plasmacytomas. The three most common caudal mandibular malignant oral tumors we see include squamous cell carcinoma, malignant melanoma, and fibrosarcoma. General practitioners also should be aware that not all oral melanomas represent a terminal diagnosis. It is now recognized that some pigmented oral tumors display a less aggressive biological behavior and can be managed surgically, with or without adjunct immunotherapy.

Incisional biopsies of soft tissue masses can be obtained by general practitioners using the following guiding principles and technique.  A biopsy is only as good as the sample, so a full-thickness, representative sample of the pathology is required.2 Avoid areas containing inflamed tissue, as that can interfere with diagnosis. If a malignancy is suspected, the sample should be collected from the center of the mass, without inclusion of adjacent normal tissue. For large soft tissue masses, a deep, wedge biopsy using a scalpel or a 4-6 mm disposable biopsy punch may be acceptable, provided that the sample includes deep tissue. Gentle handling of the specimen is important to avoid disrupting cellular morphology. Removing diseased tissue with electrocautery is not recommended due to alteration of cellular architecture by thermal damage. If intraoral radiographs suggest that the mass has invaded bone, special instrumentation is required (Michele trephine, bone biopsy needles), which may not be readily available in primary care facilities.

Many (but not all) caudal mandibular masses do invade bone, so curative intent surgery requires some form of mandibulectomy. Generally, surgical margins between 0.5 -1.0 cm are used for benign oral tumors and 2.0 cm or larger margins are used to excise malignant neoplasms. Cone beam computed tomography (CBCT) is a crucial imaging tool we rely on for surgical planning, as it provides a three-dimensional representation compared to two-dimensional radiographs. For example, with CBCT, we can measure the distance between the alveolar margin and the dorsal aspect of the mandibular canal to avoid trauma to  neurovascular tissues when performing a segmental mandibulectomy with preservation of the mandibular canal and ventral mandible (rim excision).

If adequate surgical margins can be attained, our preferred mandibulectomy technique for benign caudal mandibular tumors is rim excision. This technique preserves the ventral mandibular cortex so that postoperative mandibular drift does not occur and malocclusion is avoided. For more extensive benign tumors or malignant neoplasms, a caudal segmental mandibulectomy is performed. Post-operatively, mandibular drift occurs in which the intact mandible drifts toward the operated side, resulting in  palatal trauma by the mandibular canine tooth in the unoperated mandible. We preventively address that problem by performing crown reduction and endodontic treatment at the time of mandibulectomy. In select patients and with compliant owners, we may apply orthodontic buttons to the maxillary fourth premolar tooth and the lingual aspect of the mandibular canine tooth of the intact mandible. When elastic power chain is attached to the buttons, mandibular drift toward the operated side is prevented.

Client satisfaction is high and cosmetic results are generally good. Providing owners with post-op photographs of previous cases and addressing concerns to establish realistic expectations is crucial to successful outcomes.

1. Kim CG, Jeong KJ, Kim J, Vapniarsky N, Kang SS, 1. Kim SE, Jo HM. Lesion distribution based on oral biopsy and histopathology in dogs: A retrospective study of 338 cases (2015-2025). Vet J. 2026 Aug 20;320:106841. doi: 10.1016/j.tvjl.2026.106841. Epub ahead of print. PMID: 42624279.
2. Gold R. Getting the Most out of Oral and Maxillofacial Biopsy. J Vet Dent. 2026 Sep 30:8987564261492170. doi: 10.1177/08987564261492170. Epub ahead of print. PMID: 42813916.

(Click on images to expand)

A right caudal segmental mandibulectomy was performed to completely excise a highly invasive canine acanthomatous ameloblastoma.

A left segmental mandibulectomy with preservation of the ventral cortex (rim excision) was performed to remove a canine acanthomatous ameloblastoma.

An elastic power chain on the unoperated side was used to reduce mandibular drift following a right segmental mandibulectomy.