Presentation and initial examination We first met Zoey, a female spayed Samoyed, two years ago, when she was eight years old. Her owner noted an oral mass in the left rostral maxilla. The mass was arising from the palatal gingiva of tooth 203, possibly extending to the buccal surface of tooth 203 and the adjacent canine tooth 204 (Figure 1). The palatal component was slightly ulcerated and approximately 1 cm in diameter with a broad base. Tooth 204 had a crown fracture with pulp exposure. Figure 1. Gingival mass arising from the gingiva palatal to tooth 203 and buccal to tooth 204 in an eight-year-old female spayed Samoyed. Note generalized gingival hyperplasia of all maxillary incisors and complicated crown fracture of tooth 204. Photo courtesy Dr. John R. Lewis We recommended an incisional biopsy to determine what type of tumor Zoey had. Zoey was placed under general anesthesia, and full-mouth dental radiographs were obtained. Radiographs showed a mildly increased interdental space between 202 and 203 due to a soft tissue density and mild lysis at the alveolar margin (Figure 2). Soft tissue swelling was also noted lateral to tooth 204. Biopsies were obtained from the palatal portion of the mass and the buccal surface of 204. Histopathology returned as marked reactive mucosal hyperplasia with dysplasia and marked mixed inflammation. Seeking a second opinion Since the diagnosis did not match our clinical suspicions, we requested a second opinion from another pathologist. The second pathologist diagnosed the biopsies from the swelling around tooth 203 as moderate to severe ulcerative chronic active gingivitis with granulation tissue. Histopathology of the enlarged gingiva buccal to tooth 204 showed fibrogingival hyperplasia. After receiving the results of this second opinion, we had a discussion with Zoey’s owner. Based on clinical appearance, we still suspected a tumor over inflammatory or hyperplastic causes. We initially biopsied only soft tissue and, therefore, suspected a deeper biopsy that included tooth and bone may be warranted. Prior to that, we wanted to rule out an inflammatory disease that can mimic neoplasia: Wegener’s granulomatosis, a.k.a. granulomatosis with polyangiitis.1 This is a rare condition that can result in severe ulceration and red, raised tumor-like growths. Histopathology of this condition reveals granulomatous inflammation, which is different than the granulation tissue seen in Zoey’s samples. Granulomatous inflammation is defined by the presence of mononuclear leukocytes, specifically histiocytes (macrophages), which respond to various chemical mediators of cell injury. Through light microscopy, the activated histiocytes appear as epithelioid cells with round to oval nuclei, often with irregular contours and abundant granular eosinophilic cytoplasm with indistinct cell borders. They may also coalesce to form multinucleated giant cells.2 Granulomatosis with polyangiitis is not a common disease: I have seen probably less than 10 cases over 25 years. However, when I saw it, it has always been very responsive to steroid treatment. So, we placed Zoey on a two-week trial of prednisolone at a dose of 0.5 mg/kg every 12 hours. After two weeks of therapy, a recheck examination showed no evidence of shrinkage of the swellings. Therefore, Zoey was tapered off the prednisolone, and a second biopsy procedure was scheduled. Diagnosis At the second biopsy procedure, we biopsied the swelling palatal to tooth 203 and placed it in a cassette labeled “superficial.” We also removed tooth 203 and submitted it within the biopsy jar and obtained deeper bone and soft tissue samples from the area of the extracted tooth. These samples were placed in a cassette labeled “deep.” This more aggressive biopsy allowed us to obtain an accurate diagnosis: cystic conventional ameloblastoma. Zoey was then scheduled for a cone-beam CT scan and maxillectomy. The maxillectomy included teeth, bone, and soft tissue of the rostral maxilla, extending from tooth 206 on the left across the midline to tooth 102 on the right side. The portion of the maxilla was submitted to the pathologist, who confirmed the diagnosis and determined the margins were clean. Acanthomatous ameloblastoma is a very common odontogenic oral tumor in dogs. It represents up to 45 percent of all odontogenic tumors,3 but conventional ameloblastoma, also referred to as “solid/multicystic,” “central,” or “intraosseous” ameloblastoma, is a rare diagnosis. Both arise from cells responsible for the formation of the teeth, but acanthomatous ameloblastoma arises at the gingival margin, whereas conventional ameloblastoma arises deeper in the periodontium and can mimic a multilocular cyst. Though the radiographs taken at the time of the first biopsy showed no evidence of a cystic component, radiographs taken two months later showed at least two distinct cystic areas with a classic corticated rim of surrounding bone (Figures 2A and 2B). Gingival mass arising from the gingiva palatal to tooth 203 and buccal to tooth 204 inan eight-year-old female spayed Samoyed. Note generalized gingival hyperplasia of allmaxillary incisors and complicated crown fracture of tooth 204. Photos courtesy Dr. John R. Lewis Key takeaway This case is a good reminder that sometimes deeper biopsies are needed. If the pathologic diagnosis does not fit with the clinical picture, consider a deeper dive. We recently saw Zoey for a two-year anesthetized exam and radiographic recheck and are happy to report she is doing wonderfully. Though she looks a little different than she once did (Figures 3A and 3B), her zest for life and functionality are off the charts. A) Preoperative photo. B) Two years after her maxillectomy, Zoey is still her happy self. Photos courtesy Dr. John R. Lewis John R. Lewis, VMD, FAVD, DAVDC, practices at Veterinary Dentistry Specialists and teaches at Silo Academy Education Center, both in Chadds Ford, Pa. References https://www.veterinarypracticenews.com/another-zebra-diagnosis-cases-granulomatosis-with-polyangiitis/ Shah KK, Pritt BS, Alexander MP. Histopathologic review of granulomatous inflammation. J Clin Tuberc Other Mycobact Dis. 2017 Feb 10;7:1–12. Fiani N, Verstraete FJ, Kass PH, Cox DP. Clinicopathologic characterization of odontogenic tumors and focal fibrous hyperplasia in dogs: 152 cases (1995-2005). J Am Vet Med Assoc. 2011 Feb 15;238(4):495-500.
