Ventral mandibulectomy for removal of oral tumours in the dog: Surgical technique and results in 19 cases

The purpose of this retrospective study is to describe in detail a novel ventral approach for mandibulectomy and the results in 19 dogs. The medical records of 19 dogs that received a partial or total unilateral mandibulectomy with the new ventral approach were reviewed. Information obtained included signalment, tumour type, extent of mandibulectomy, removal of regional lymph nodes, intrasurgical complications, immediate postoperative complications, histopathological diagnosis and study of margins. Intrasurgical complication occurred in one dog (haemorrhage) and required a blood transfusion. Postoperative morbidity was minor and included transient ventral cervical swelling and self‐limiting sublingual swelling (two dogs). All 19 animals were discharged between 24 and 48 hours of the procedure, and appetite was considered normal at discharge. Some perceived advantages of this procedure include easy identification of all the important anatomic structures in the area, including the inferior alveolar artery and temporo‐mandibular joint, and the fact that osteotomy of the zygomatic arch is not necessary (in case of caudal mandibulectomy). In addition, dissection of both mandibular and retropharyngeal lymph nodes is easily achieved by caudal extension of the same skin incision.     

Results of Partial Mandibulectomy for the Treatment of Oral Tumors in 142 Dogs

Partial mandibulectomy was performed for the treatment of benign or malignant oral tumors in 142 dogs. Forty-two dogs with a benign tumor (ameloblastoma) had a 22.5 month (range, 6 to 74 months) median disease-free interval, with a 97% 1-year survival rate; there was local recurrence in one dog. Twenty-four dogs with squamous cell carcinoma had a disease-free interval of 26 months (range, 6 to 84 months), with a 91% 1-year survival rate; recurrence and metastasis developed in two dogs and metastatic disease in one dog. Based on survival curves, 37 dogs with a melanoma had a median survival time of 9.9 months (range, 1 to 36 months), with a 21% 1-year survival rate; 20 dogs died or were euthanatized for recurrent or metastatic disease. Twenty dogs with osteosarcoma had a median survival time of 13.6 months (range, 3 to 28 months), with a 35% 1-year survival rate; nine dogs died or were euthanatized for recurrent or metastatic disease. Nineteen dogs with fibrosarcoma had median survival time of 10.6 months (range, 3 to 32 months), with a 50% 1-year survival rate; 12 dogs died or were euthanatized for recurrent or metastatic disease. Results of this and previous studies demonstrated that partial mandibulectomy was effective in prolonging survival and decreasing recurrence for squamous cell carcinoma and ameloblastoma. Progressive disease and corresponding low survival times were common in dogs with melanoma, osteosarcoma, and fibrosarcoma. There were no differences in survival times or the progression of disease among five partial hemimandibulectomy procedures. The high rates of recurrence and metastasis in dogs with these tumors suggest a need for evaluation of ancillary chemotherapy and local radiation therapy to decrease the prevalence of progressive disease.     

Compound odontoma in three dogs

Three young, female dogs were operated for compound odontoma. All tumors were considered stage III with treatment consisting of partial mandibulectomy or maxillectomy. Microscopic examination of the resected tissue confirmed the diagnosis. Relatively aggressive, resective surgery resulted in prolonged tumor-free intervals.     

Mandibular Rim Excision in Seven Dogs

Objective— To describe a surgical technique for excision of minimally invasive mandibular tumors at the level of the premolar and molar teeth, and report outcome in 7 dogs that had mandibular rim excision. Study Design— Case series. Animals— Dogs (n=7) with a mandibular tumor at the level of the premolar and molar teeth. Methods— Using an intraoral approach to the mandible, buccal, and lingual mucosal incisions are made to obtain a 10 mm clean margin beyond neoplastic tissue. After subperiosteal soft tissue elevation, a curvilinear rim mandibulectomy is performed, leaving the mandibular canal and ventral cortex intact, followed by osteoplasty. The remaining attached gingiva and alveolar mucosa are sutured over the bony defect. Results— Seven dogs were treated (1997–2008) for odontogenic and early malignant neoplasms involving the mandible by mandibular rim excision. All dogs had healed, healthy gingival covering over the surgical defect, very good postoperative function, and good quality of life. Conclusion— Mandibular rim excision, with preservation of the ventral cortex and mandibular canal content, can be a good option for treatment of early odontogenic and malignant lesions of the mandible in medium to large breed dogs. Clinical Relevance— In medium to large dogs with minimally invasive mandibular neoplasia, mandibular rim excision should be considered as a viable surgical option.     

Rostral Mandibulectomy Three Case Reports in Dogs

A rostral mandibulectomy was performed on three dogs with mandibular neopiasia. The technique involves stabilization of the mandibular rami, excision of the mandible rostral to the frenulum of the tongue, and cosmetic closure of the wound. Two patients were living 11 months postoperatively. This technique is effective in treating some malignant neoplasms of the rostral mandible.     

Wide Local Excision of Acanthomatous Epulides in the Dog

Twenty-five dogs bearing acanthomatous epulides of the oral cavity underwent tumor resection by wide local excision. The surgical procedures included rostral mandibulectomy, removal of the mandibular body, premaxillectomy, and partial maxillectomy. Postoperative complications were rare, and local recurrence was not encountered in any dogs over periods of 1 to 6 1/2 years (median, 22 months). The authors conclude from the high incidence of local recurrence after simple excision through the tumor margins and the potential for malignant transformation after irradiation that wide surgical resection is the technique of choice for the management of acanthomatous epulis.     

Ameloblastoma and keratinizing ameloblastoma in dogs

Ameloblastomas reviewed in this report were locally invasive neoplasms arising from the epithelial structures of the dental lamina, and were characterized histologically by features which are unique to dental lamina epithelium. These include the formation of epithelial sheets in which the cells nearest the stroma form a palisading row aligned perpendicularly to the basement membrane and the cells toward the center separate from each other except at desmosomal attachments. This is similar to the appearance of th stellate reticulum of the early enamel organ. Other features include epithelial cords which branch and interconnect, and the intimate association of epithelial structures and collagenous matrix. In our dogs, other important features were the deposition of inclusions similar in appearance to enamel matrix between the cells of the epithelium and various degrees of keratinization. All ameloblastomas studied were locally invasive tumors which occurred at various sites on the gingiva. The average age of the dogs was 8.7 years and the age range was three to 13 years. Radiographically, all of the tumors studied resulted in periodontal osteolysis. Six dogs were treated with radiation therapy, but details of the radiotherapy of two dogs could not be located. Of the other four dogs, one is alive 48 months after radiotherapy with no evidence of tumor regrowth. Regrowth of the oral tumor was apparent in the other three dogs six, 21, and 34 months after completion of the radiotherapy. Three dogs were treated by radical mandibulectomy; all are alive with no evidence of tumor recurrence at two, 20, and 28 months postoperatively. Two dogs had local dissection (curettage) of tumors and the tumors recurred at 12 and 15 months after surgery. One dog was euthanatized after diagnosis of the oral tumor because of a progressive neuropathy.     

Biological behaviour of canine mandibular osteosarcoma. A retrospective study of 50 cases (1999–2007)

The purpose of this retrospective study was to describe the biological behaviour of canine mandibular osteosarcoma (OSA) and to examine factors for their impact on metastasis‐free interval (MFI) and survival time (ST). Records from dogs treated with mandibulectomy for OSA (1999–2007) were reviewed. Archived tumour samples were evaluated for mitotic index (MI) and tumour grade. Fifty dogs were included, 21 received chemotherapy. Twenty‐nine dogs (58%) developed metastatic disease. The median MFI was 627 days, and median ST was 525 days. In univariate analysis MI > 40 was prognostic for decreased MFI and ST. Grade also influenced MFI and ST, with 5/21 (24%) dogs with grade II/III tumours metastasis‐free at one year versus 16/22 (72%) dogs with grade I tumours (P = 0.002); and 5/21 (24%) dogs with grade II/III tumours alive versus 17/22 (77%) dogs with grade I tumours (P = 0.001). In multivariate analysis, histological grade and adjuvant chemotherapy were prognostic for MFI and ST.     

Immediate mandibular reconstruction of a 5 cm defect using rhBMP-2 after partial mandibulectomy in a dog

Objective— To report treatment of a complex odontoma of the mandible by partial mandibulectomy and immediate surgical reconstruction using bridging plate fixation with a synthetic graft.
Study Design— Clinical case report.
Animals— A 4-year-old male castrated cocker spaniel.
Methods— Immediate reconstruction of the left mandible (5 cm gap) was performed after complete excision of a complex odontoma. Locking plate fixation was applied immediately before complete excision of the mass. Fixation was removed, then after partial mandibulectomy, including all abnormal tissue, restored to achieve occlusion. The resulting mandibular defect was filled with recombinant human bone morphogenetic protein-2 (rhBMP-2) delivered in an absorbable collagen sponge containing hydroxyapatite/tricalcium phosphate granules (compression resistant matrix [CRM]).
Results— New bone growth was evident radiographically and on palpation at 3 months. Bony remodeling was evident during follow-up examinations up to 26 months. Bone collected by biopsy at the graft site at 7 months had robust new bone formation and evidence of continued remodeling. Only minor complications (repeated intraoral plate exposure) were encountered postoperatively and were easily resolved.
Conclusions— An osteoinductive factor (rhBMP-2/CRM) was successfully used as a graft substitute in immediate reconstruction of a large mandibular defect.
Clinical Relevance— Immediate reconstruction of large mandibular defects with osteoinductive materials as a graft substitute may be a viable alternative to partial mandibular resection or radiation therapy for benign odontogenic tumors in dogs.     

Miniplate Fixation for Repair of Mandibular and Maxillary Fractures in 15 Dogs and 3 Cats

Maxillofacial miniplates and screws were used for skeletal fixation in 15 dogs and 3 cats that sustained a variety of mandibular and maxillary fractures. These implants were used as neutralization or buttress fixation in 11 caudal (junction of the ramus with the mandibular body) and 2 rostral mandibular fractures, 4 maxillary fractures, and 2 zygomatic arch fractures. All but one of the fractures healed with appropriate occlusion and excellent function. In one case of a rostral mandibular fracture, soft tissue dehiscence occurred accompanied by a loss of the fixation and subsequent distraction of the bone fragments; reasonable function was obtained by performing a rostral mandibulectomy. Plate contouring and application of the miniplates along the appropriate biomechanical lines of stress was easily performed and permitted the biomechanical principles of tension band fixation to be applied in most cases. Miniplate fixation, either used alone or in combination with other fracture fixation techniques, achieved sufficiently rigid skeletal fixation to provide uncomplicated healing and good to excellent functional and cosmetic results in 14 dogs and 3 cats.     

Outcomes of cats with oral tumors treated with mandibulectomy: 42 cases

Medical records of 42 cats treated with mandibulectomy for oral neoplasia at eight institutions were reviewed to determine morbidity, progression-free interval, and survival time. Progression-free and survival rates at 1 and 2 years were 56% and 49%, and 60% and 57%, respectively. Cats with squamous cell carcinoma had significantly shorter survival than cats with fibrosarcoma or osteosarcoma. Seventy-two percent of cats were dysphagic or inappetent immediately postoperatively, and 12% never regained the ability to eat. Despite acute morbidity in 98% and long-term morbidity in 76% of cats, 83% of the 30 owners providing information were satisfied with the outcome of mandibulectomy.     

Rostral mandibulectomy in five horses.

Rostral mandibulectomy with primary gingival closure was performed in 5 horses with rapidly growing or bleeding mandibular tumors. The technique involved preservation of the most caudal portion of the mandibular symphysis to maintain stability. There were no surgical complications or recurrences, and the cosmetic and functional results were good. The histopathologic diagnosis of all the tumors was ossifying fibroma. Rostral mandibulectomy affords a simple and effective technique of treating tumors of the rostral portion of the mandible in horses.     

Surgical correction of temporomandibular joint ankylosis in two cats

Two cats with temporomandibular joint ankylosis were examined. Difficulty in opening the mouth and malocclusion were associated with trauma and fracture around the zygomatic arch and the condyle of the mandible after an automobile accident. Unilateral condylectomy or aggressive caudal mandibulectomy was performed to improve quality of life. Excision arthroplasty of the temporomandibular joint improved mandibular function and appearance. Some malocclusion remained but had no clinical significance.     

Results of surgical treatment for hyperadrenocorticism caused by adrenocortical neoplasia in the dog: 25 cases (1980-1984)

Results of surgical treatment for neoplasia of the adrenal cortex that caused hyperadrenocorticism were evaluated in 25 dogs. Surgical examination of the adrenal glands was performed by use of a ventral midline approach in 24 dogs and a retroperitoneal approach in 1 dog. All 25 dogs had a unilateral, adrenocortical tumor. Histologic examination identified 14 adrenocortical carcinomas and 11 adenomas. Seven dogs with carcinoma had visible metastasis to the liver, 3 had local invasion into the caudal vena cava, and 1 had extension into the adjacent renal vein. Seven of the 9 dogs with metastasis were euthanatized at time of surgery. Of the remaining 18 dogs that survived surgery, 9 (4 with carcinoma and 5 with adenoma) developed serious postoperative complications including acute renal failure, pneumonia, and pulmonary artery thromboembolism; 8 of these dogs died or were euthanatized. Of the remaining 10 dogs, clinical signs associated with hyperadrenocorticism resolved in the 7 dogs that had adrenocortical adenoma and in 1 of the 3 dogs that had carcinoma. The remaining 2 dogs with carcinoma had persistent hyperadrenocorticism and were treated with high doses of mitotane. Although no response was observed in 1 dog with visible hepatic metastasis, a decrease in serum cortisol concentrations and resolution of clinical signs were detected in the other dog during prolonged daily administration of mitotane.     

MAGNETIC RESONANCE IMAGING FINDINGS IN 25 DOGS WITH INFLAMMATORY CEREBROSPINAL FLUID

To describe the signs that may be associated with intracranial inflammatory conditions, magnetic resonance (MR) images of 25 dogs that had inflammatory cerebrospinal fluid (CSF) were mixed with those of a control group of 40 dogs that had CSF negative for inflammatory disease and reviewed without knowledge of the clinical signs or diagnosis. CSF was considered inflammatory if the protein level was > 0.25 g/l and the white cell count was > 5 mm(-3). Abnormalities were found by MR imaging in 19 (76%) dogs with inflammatory CSF. Two dogs had focal lesions, 10 had multifocal lesions, and seven had diffuse lesions. Lesions affected all divisions of the brain. Mass effect was identified in seven (28%) dogs, including one that had a choroid plexus carcinoma. Lesions were hyperintense in T2-weighted images in 18 dogs and hypointense in T1-weighted images in six dogs. Multifocal or diffuse intraaxial lesions that were hyperintense in T2-weighted images were observed in 17 (68%) dogs with inflammatory CSF. Administration of gadolinium resulted in enhancement of intraaxial lesions in nine (36%) dogs and enhancement of meninges in seven (28%) dogs. Six (24%) dogs with inflammatory CSF had images interpreted as normal.     

Factors associated with long-term survival in dogs undergoing liver lobectomy as treatment for liver tumors

The objectives of the study were to describe clinicopathologic findings in dogs that underwent surgical treatment of liver tumors and to define outcome-associated variables in this canine population. Medical records of 118 dogs that underwent liver lobectomy were reviewed. Variables were assessed via univariate and multivariate Cox regression analyses. Hazard ratios, median survival times (MSTs), and Kaplan-Meier Survival curves (KMSCs) were created for significant variables. Of the dogs with surgically addressed hepatic tumors, 93% survived to discharge. The MST was not reached. Lethargic dogs had a mortality risk 10.2 times that of non-lethargic dogs. Non-tachypneic dogs had a mortality risk 4.3 times that of tachypneic dogs. Dogs that experienced anesthetic complications had a mortality risk 100 times that of dogs that did not. We conclude that the prognosis associated with liver tumors is good. Lethargy, respiratory rate, and anesthetic complications were associated with outcome.     

A Comparison of Medullary Thyroid Carcinoma and Thyroid Adenocarcinoma in Dogs: A Retrospective Study of 38 Cases

The medical records of 38 dogs with thyroid neoplasia that were treated by surgical excision of the tumor, or had an incisional biopsy performed as a diagnostic procedure, were reviewed. Of the 38 dogs, 21 (55%) had resectable tumors, whereas 17 (45%) had an incisional biopsy as the tumors were nonresectable. All dogs had an initial diagnosis of thyroid carcinoma. The type of carcinoma was confirmed in 33 dogs by histological and immunohistochemical examination. Twelve dogs (36%) had medullary thyroid carcinoma, and 21 dogs (64%) had thyroid adenocarcinoma. Of the 12 dogs with medullary thyroid carcinoma, 10 (83%) had resectable tumors. Of the 10, three (30%) had at least a 1-year survival. None had radiographic evidence of metastasis at the time of surgery. Of the 21 dogs with thyroid adenocarcinoma, 11 (52%) had resectable tumors. Of the 11 dogs, five (45%) had at least a 1-year survival. Three dogs had radiographic evidence of metastasis at the time of surgery. Of 10 dogs with nonresectable thyroid adenocarcinoma, two dogs (20%) had at least a 1-year survival. In the dogs in this study, medullary thyroid carcinoma was more prevalent than previously reported. Most of the medullary thyroid carcinomas were well circumscribed and resectable. Medullary thyroid carcinoma may possess gross and histological characteristics of a less malignant nature when compared with other thyroid carcinomas.     

Frequency and severity of mastocytemia in dogs with and without mast cell tumors: 120 cases (1995-1997).

OBJECTIVE: To elucidate frequency of detection on blood smears and severity on quantitative buffy coat evaluation of mastocytemia between dogs without mast cell tumors (MCT) and dogs that had MCT, and to expand the list of diseases associated with mastocytemia in dogs without MCT. DESIGN: Retrospective study. ANIMALS: 94 dogs without MCT and 26 dogs with MCT. PROCEDURE: Medical records of all dogs with mast cells detected on blood or buffy coat smears during a 2-year period were reviewed. Dogs with mastocytemia were grouped by disease into dogs with MCT and dogs without MCT. Twenty-five of the dogs without MCT that had mast cells detected on blood smears also had evaluations of buffy coat smears. Quantitative buffy coat results of the 25 dogs without MCT were compared with those of the 26 dogs with MCT. RESULTS: 95.5% of blood smears with mast cells detected during CBC determination were from dogs without MCT. For these dogs, diagnoses included inflammatory disease (28.2%), regenerative anemia (27%), neoplasia other than MCT (25.9%), and trauma (11.8%). Dogs with MCT had a mean of 71.4 mast cells/buffy coat smear, whereas dogs without MCT had a mean of 276.2 mast cells/buffy coat smear. The 2 highest counts of mast cells/buffy coat smear were for dogs without MCT. CONCLUSIONS AND CLINICAL RELEVANCE: On the basis of results of quantitative buffy coat evaluations, severity of mastocytemia in dogs without MCT often exceeds that detected during tumor staging in dogs with MCT. Random detection of mast cells in blood smears during CBC determination in dogs is usually not secondary to MCT.     

Prevalence of hemangiosarcoma in anemic dogs with a splenic mass and hemoperitoneum requiring a transfusion: 71 cases (2003-2005)

OBJECTIVE: To determine prevalence of splenic hemangiosarcoma in anemic dogs with a splenic mass and hemoperitoneum requiring a transfusion and to identify factors that could differentiate between dogs with hemangiosarcoma and dogs with other splenic masses at the time of hospital admission. DESIGN: Retrospective case series. ANIMALS: 71 dogs. PROCEDURES: Medical records, blood bank logs, and histologic reports of dogs with a splenic mass and hemoperitoneum that required a transfusion between 2003 and 2005 were reviewed. Dogs that received a transfusion of packed RBCs, were splenectomized, and had a definitive histologic diagnosis were included. RESULTS: Signalment of dogs was similar to that in other reports. Malignant splenic neoplasia was identified in 54 of 71 (76.1%) dogs, whereas 17 of 71 (23.9%) dogs had a benign splenic lesion. Of 54 dogs with malignant splenic neoplasia, 50 (92.6% [70.4% of all dogs]) had splenic hemangiosarcoma. In addition, dogs with splenic hemangiosarcoma had significantly lower total solids (TS) concentrations and platelet counts at admission. Finally, hemoperitoneum was strongly associated with a diagnosis of splenic hemangiosarcoma. CONCLUSIONS AND CLINICAL RELEVANCE: In this clinical population of dogs, prevalence of hemangiosarcoma was higher than in other studies. Dogs with hemangiosarcoma in this study had significantly lower TS concentrations and platelet counts at the time of admission, compared with values for dogs with other splenic masses. No other markers were useful in differentiating dogs with hemangiosarcoma. It is important to discuss the prevalence of and poor prognosis associated with hemangiosarcoma with owners when they are contemplating whether to proceed with treatment.