Non-invasive and Locally Invasive Hypercellular Peripheral Odontogenic Fibroma in 20 Dogs

Medical records of dogs with an initial histopathological diagnosis of odontogenic sarcoma were reviewed for information on signalment, body weight, medical history, clinical signs, physical examination and diagnostic imaging findings, surgical procedure performed, and histologic characteristics. Twenty dogs were deemed to fit the criteria following the rigorous histology review process. These tumors were characterized by hypercellularity of the spindle cell component with less intervening stroma, mitotic activity, and variable presence of odontogenic epithelium and hard substance (cementum/dentin/bone). Non-invasive or locally invasive hypercellular peripheral odontogenic fibroma is suggested by the authors to describe these tumors. There were no signs of recurrence of any of the masses following surgical excisions with varying margins.

Malignant Ameloblastic Fibro-odontoma in a Dog

An 11-year-old male Collie was presented with a swelling of the face caused by tumor masses arising from the gingiva. Postmortem examination revealed metastases to the lymph nodes, lung, liver, and orbital cavity. Histologically, the tumor represented a combination of fibrosarcomatous proliferation, pulpal mesenchyme, and undifferentiated odontogenic epithelium, with a follicular or plexiform growth pattern. In addition, the follicular areas of the tumor showed a biphasic character, and there were numerous apoptotic cells in plexiform areas. Furthermore, acidophilic material resembling dysplastic dentine or enamel matrix was observed in the metastatic lesion in the lung. Based on the histological characters, the present case was diagnosed as malignant ameloblastic fibro-odontoma. This study is the first known description of a possible malignant ameloblastic fibro-odontoma in a dog with metastasis to distant organs.

Gingival rhabdomyosarcoma accompanied by an immature myogenic population immunoreactive for α-smooth muscle actin in a dog

A 3-year-old female shih tzu was presented with a white to dark red mass arising from the gingiva. Because of the rapid and invasive growth of the mass, the dog was humanely destroyed. Microscopically, round to polygonal anaplastic cells with strongly eosinophilic cytoplasm grew in an alveolar pattern separated by fibrous stroma. Mitotic figures were numerous. Multinucleated cells and 'strap cells' were observed, but cross striation and glycogen accumulation were absent. Immunohistochemically, the tumour cells were positive for vimentin, desmin, muscle-specific actin and MyoD1, and a small number of tumour cells were positive for α-smooth muscle actin (α-SMA). Based on the morphological and immunohistochemical features, the gingival mass was diagnosed as alveolar rhabdomyosarcoma accompanied by α-SMA-positive immature myogenic cells.

Insulinoma and squamous cell carcinoma with peripheral polyneuropathy in an aged Sprague-Dawley rat

Pancreatic islet cell adenoma, oral squamous cell carcinoma, peripheral polyneuropathy, and multiple age-associated degenerative lesions were diagnosed in an aged Sprague-Dawley rat presenting with polyuria, polydypsia, dehydration, anorexia, weight loss, and posterior weakness. Microscopically, the islet cell adenoma was encapsulated by fibrous tissue and composed of packets of oval-to-polygonal monomorphic cells in a fibrovascular stroma. Immunohistochemically, the majority of cells within the mass expressed insulin. In light of the histologic and immunohistochemical findings, a diagnosis of insulinoma was made. The oral squamous cell carcinoma, grossly presenting as gingival ulceration, was composed of nests and cords of squamous epithelial cells that focally eroded and infiltrated the hard palate and resulted in degeneration of the maxillary nerve. The peripheral polyneuropathic lesions were characterized by extensive axonal degeneration and microangiopathic changes that were highly suggestive of a hypoglycemic etiopathogenesis secondary to insulinoma.

Amyloid-producing odontogenic tumor and its immunohistochemical characterization in a Shih Tzu dog

A 10-year-old, male, Shih-Tzu dog presented with swelling of the right lower jaw caused by a mass arising from the right mandibular gingiva. Radiographic examination revealed bone lysis of the right wing of the mandible. Histopathologically, the growth was characterized by indistinctly lobulated nests, islands, and strands of proliferating odontogenic and squamous epithelial cells, intermingled in close association with large numbers of irregular extracellular deposits of amyloid and amorphous calcified substance. Immunohistochemically, both epithelial components stained strongly positive for cytokeratin (AE1/AE3); the squamous epithelial cells also reacted strongly with neuron-specific enolase (NSE) and S-100 protein, whereas the odontogenic epithelial cells displayed weak immunoreactivity to NSE and partial reactivity to S-100 protein. The amyloid deposits were AE1/AE3-negative. The growth was diagnosed as an amyloid-producing odontogenic tumor.

Extranodal lymphoblastic lymphoma of suspected B-cell lineage in the gingiva of a racehorse, accompanied by mandibular osteolysis

A mass developed in the mandibular gingiva of a thoroughbred racehorse. When the horse could no longer eat unassisted, it was killed and immediately autopsied. Macroscopically, the mandible exhibited extensive osteolysis, with only a small amount of bone remaining around the tooth roots. The cut surface of the mass around the mandible consisted of neoplastic medullary tissue, in which osteogenesis was observed. The medullary tissue was composed of pleomorphic medium-sized to large cells, interlaced by collagen bundles. These cells had large, pale, round or ovoid, sometimes cleaved nuclei, with one or two prominent nucleoli. Mitoses were numerous. Electron microscopy showed that the cells in the medullary tissues were similar in shape to undifferentiated lymphocytes. Immunohistochemically, these cells were positive for B-cell associated antigen in the pre-B-cell stage. Our findings suggest that the horse had extranodal lymphoblastic lymphoma of suspected B-cell lineage, possibly originating from the lymphatic system of the gingiva. We consider that the osteolysis resulted from activation of osteoclasts by proliferation of the tumour cells.

Recurrent ossifying epulis in a dog

A seven-year-old neutered/male Siberian Husky-cross dog was referred for evaluation of a gingival mass. Two years previously, the referring veterinarian had resected an ossifying epulis from the same area between the maxillary left first and second premolars. The neoplasm recurred 4-months after the original surgery. En bloc resection provided tumor-free margins. An oral examination 12-months following surgery indicated no gross signs of recurrence.

Apparent pokeweed mitogen cure of metastatic gum melanoma in an older dog

Immunotherapy with plant mitogens has been of increasing interest to both authors, although their mutual attraction to these substances over the past two decades occurred independently and has taken divergent pathways from the start. Because of their clinical unavailability, Wimer's efforts have been confined to writing theoretical concepts on potential applications of the mitogens focusing on the L4 isolectin of PHA. Alternatively, Mann has worked actively with laboratory and experimental research involving PWM that he has extracted himself. As a sequel to a pilot study of PWM cancer treatment in pets whereby he supplies the mitogen, protocol, and data sheets and veterinarians supervise the administration, Mann acquiesced to widespread requests for inclusion in an extended investigation. Unfortunately, this arrangement has left Mann with little control over data submission, and until recently, only verbal reports have been received. The recent documentation of a three-year remission and apparent cure of gum melanoma metastatic to regional and hilar lymph nodes and to the lungs in an aged dog following PWM therapy has prompted this case report. The incredible response has inspired more aggressive attempts to obtain information from other recipients of the mitogen. The small total dose of 300 micrograms inducing a remission does speak for the remarkable potency of PWM that may be 500 or more times that of PHA. However, the possibility that melanoma is a uniquely responsive tumor is suggested by a 1971 article indicating complete remission of metastatic melanoma in an 18-year-old lad to an unexpectedly low total dose of 50 mg PHA. Preliminary reports on other tumors treated with PWM indicate some impressive responses have occurred, although they also suggest that Mann's regimen may sometimes require adjustments in dosages and other variables previously reviewed in theoretical PHA-L4 models, to which this case report now contributes validity.

Use of a free cortical ulnar autograft following en bloc resection of a mandibular tumor

A dog was presented for the en bloc resection of a previously irradiated mandibular ossifying epulis. A central hemimandibulectomy was performed, and the mandibular defect was stabilized by the use of a free cortical ulnar autograft and rigid internal fixation. The dog had normal mastication and left forelimb function two weeks after surgery. Radiographic evaluation of the surgical site at three and 10 months after surgery showed normal bony healing.

Proliferative potential of canine oral epulides and malignant neoplasms assessed by bromodeoxyuridine labeling

The proliferative potential of canine oral lesions, including epulides, squamous cell carcinomas, a malignant melanoma, and a fibrosarcoma, was examined using a monoclonal antibody to bromodeoxyuridine (BrdU). Twenty-three dogs with oral masses were administered BrdU intravenously at a dose of 8 mg/kg 1 hour before surgery, and the BrdU labeling index (LI) of each lesion was determined immunohistochemically. The average BrdU LIs for the main proliferating elements in the fibromatous epulis (4 cases), ossifying epulis (2 cases), and acanthomatous epulis (10 cases) were 4.9, 3.0, and 8.8%, respectively. The squamous cell carcinomas (5 cases) had an average LI of 15.9%, and the LIs of the malignant melanoma and fibrosarcoma were 7.5 and 10.3%, respectively. All cases of acanthomatous epulides and squamous cell carcinoma treated with simple marginal surgical resection recurred within a short time. The higher LIs in the acanthomatous epulides, squamous cell carcinomas, and fibrosarcoma correlate well with their poor prognoses, reflected by rapid growth and frequent recurrence. Acanthomatous epulis is clearly distinguished from other epulides by its aggressive clinical behavior and high proliferative potential, which is equivalent to that of malignant tumors, despite a lack of cell atypia. The BrdU LI is a useful marker for evaluating the proliferative potential and prognosis of canine oral tumors.

Oral malignant melanoma with osteoid formation in a dog

Melanomas are the most frequent malignant neoplasms of the oral cavity of dogs. Osteogenic melanoma is a rare variant of melanoma that has been described in humans but not in animals. We describe a case of malignant melanoma with bone production affecting the gingiva of a 12-year-old Miniature Dachshund dog. The tumor was a round, lightly pigmented mass that measured 1 cm in diameter and was hard to cut. Histologically, the tumor was composed of nests and lobules of anaplastic, round, melanin-containing cells supported by a stroma displaying abundant osteoid matrix. Many of the neoplastic melanocytic cells were in close contact with the osteoid trabeculae. Immunohistochemical tests revealed that the neoplastic cells were immunoreactive for S-100 and vimentin and showed no staining with cytokeratin. The animal had a local recurrence of the tumor 3 months after the initial excision. This is the first case of malignant melanoma with osteoid formation reported in animals.

The effect of intralesional bleomycin on canine acanthomatous epulis

Four dogs with recurrent acanthomatous epulis (AE) were injected with bleomycin (5 mg) intralesionally once a week. In three cases, tumors were clinically indistinguishable within three-to-eight weeks. In the fourth case, the tumor disappeared after 10 weekly injections. Through the administration period of bleomycin, no adverse reactions were recognized in any case. Electron microscopic examination together with a decrease in the percentage of mitotic cells implied that bleomycin might inhibit deoxyribonucleic acid (DNA) synthesis of tumor cells.

Amelogenin expression in canine oral tissues and lesions

Amelogenins are major enamel proteins within the enamel extracellular matrix. The expression of amelogenin was confirmed in neonatal tissues of the canine jaw. The sequence of a portion of canine amelogenin cDNA, within exons 5 and 6, was determined and found to be closely homologous to sequences reported in the cow, pig, mouse and human being. Two acanthomatous epulides collected from clinically affected dogs showed amelogenin expression, whereas 22 other canine oral lesions, including six additional acanthomatous epulides, did not show amelogenin expression. Examination of structural proteins may allow precise identification of the histogenesis of the odontogenic neoplasms, which are often difficult to distinguish by means of morphological criteria alone.

Functional loss of p21/Waf-1 in a case of benign canine multicentric melanoma

Mutations of tumor suppressor genes remove mechanisms that normally arrest proliferation of transformed cells, resulting in tumor formation. The p53 gene product functions as a tumor suppressor that induces p21/Waf-1, the 21-kDa product of the waf-1/cip-1/mda-6 gene. p21/Waf-1 is a pan-cyclin-dependent kinase inhibitor that arrests cell cycle progression under a variety of circumstances. We examined tissues from a dog with multiple primary pigmented proliferative lesions (benign, multicentric melanoma consisting of three distinct dermal lesions and a matrical cyst) for p21/Waf-1 and p53 expression by immunohistochemistry and immunoblotting. p21/Waf-1 and p-53 proteins were undetectable in the tumor cells and in the cyst but were present in adjacent normal tissues. Abundant cyclin-dependent kinase 4 (Cdk4), a protein related functionally to p21/Waf-1, also was present in the cyst. A somatic mutation of the waf-1 gene or of the p53 gene may have resulted in the loss of p21/Waf-1 expression in a common precursor of pigment-producing cells from the affected dog. Furthermore, this functional loss of p21/Waf-1 may play an important role in the genesis of canine benign melanoma.

Gingival vascular hamartoma with associated paraneoplastic hyperglycemia in a kitten

A 4-month-old domestic shorthair cat was examined because of a maxillary gingival mass that had regrown following excisional biopsy. The kitten also had a history of persistently high blood glucose concentrations, despite 2 weeks of insulin treatment. Radiography revealed maxillary alveolar bone lysis and displacement of multiple teeth. Partial maxillectomy was performed to remove the mass, which histologically was a gingival vascular hamartoma. Hyperglycemia permanently resolved < 24 hours after mass removal. On the basis of the temporal relationship between mass removal and resolution of hyperglycemia, as well as the lack of evidence of any concurrent disease, hyperglycemia in this cat was considered to be a paraneoplastic syndrome.

Epulides in the dog: a review

This article is based on a review of the literature and the study of pathology sections obtained from various veterinary pathology laboratories. Epulis is a non-specific, clinical designation for a localized, exophytic growth on the gingiva. Four reactive epulides occur in human beings, namely focal fibrous hyperplasia (fibrous epulis), pyogenic granuloma, peripheral giant cell granuloma (giant cell epulis), and peripheral ossifying fibroma (calcifying fibrous epulis). The first three also occur in dogs but only focal fibrous hyperplasia appears to be common. The peripheral ossifying fibroma has not yet been reported in dogs. Odontogenic tumors occurring on the gingiva (i.e., as epulides) are referred to as peripheral odontogenic tumors. Three types have been reported in dogs. One, the common fibromatous epulis, is equivalent to the rare peripheral odontogenic fibroma in human beings. Another, the acanthomatous epulis, appears to be a form of ameloblastoma but differs from the peripheral ameloblastoma in human beings in that it invades bone; its biological behavior is therefore that of the human intraosseous ameloblastoma. The third, a rare lesion, has been referred to in the veterinary literature as a calcifying epithelial odontogenic tumor, although it is not the canine counterpart of the human CEOT. The term, amyloid-producing odontogenic tumor, has been suggested as being appropriate for this lesion.

Canine acanthomatous epulis. The only common spontaneous ameloblastoma in animals

This article describes the acanthomatous epulis in dogs, a quite common lesion that appears to be the counterpart of human ameloblastoma. Histologically, it resembles closely the acanthomatous pattern of human ameloblastoma and, like ameloblastomas in human beings, it infiltrates cancellous bone; moreover, it has no tendency to metastasize. Veterinarians have sometimes treated the acanthomatous epulis with therapeutic irradiation, providing one example when this tumor served as an animal model for human ameloblastoma. Although this treatment has cured some animals, others have developed postirradiation malignancies.

Light microscopic, ultrastructural, and immunohistochemical examinations of two calcifying epithelial odontogenic tumors (CEOT) in a dog and a cat

Two calcifying epithelial odontogenic tumors from a 10-year-old cross-breed dog and a 9-year-old cat were characterized histologically and electron microscopically. Important characteristics were plexiform to squamous epithelial structure, amyloid in the tumor tissue with partial calcification (Liesegang's rings), and a low rate of mitosis. The amyloid found in the tumors was subjected to immunohistochemical examination, using a series of antibodies (anti-AA, -AL, -AF, -ASc1, -AB, -cytokeratin, -vimentin, -desmin, -laminin). The exclusive reaction to anti-cytokeratin and anti-laminin suggests that the amyloid is of epithelial origin.

The relationship of the canine acanthomatous epulis to ameloblastoma

This paper compares the microscopic features and clinical behaviour of the acanthomatous epulis in dogs with those of ameloblastoma in human beings. The acanthomatous epulis has similar microscopic features to one histological variant of human ameloblastoma, the acanthomatous ameloblastoma. Moreover, its clinical behaviour is equivalent to that of intraosseous ameloblastoma in human beings, not of the human peripheral (extraosseous) ameloblastoma, as has been suggested. The stroma of acanthomatous epulides varies and does not always resemble periodontal ligament, a feature that in dogs has been used to distinguish them from ameloblastomas. It is concluded that the acanthomatous epulis (1) is an ameloblastoma, (2) arises from the gingival epithelium in some cases, but (3) may also arise intraosseously and then break out of bone. We recommend the term canine acanthomatous ameloblastoma as being appropriate for this lesion.

The histological nature of epulides in dogs

The histological characteristics of a series of 154 oral tumours with the clinical appearance of epulides in 129 dogs were reviewed. Diagnoses were based on current criteria in human oral pathology and compared with the original diagnoses. The histological findings suggested that the majority of epulides in the dog can be classified as focal fibrous hyperplasia (43.5 per cent), peripheral ameloblastoma (17.5 per cent), peripheral odontogenic fibroma (WHO type) (16.9 per cent) and pyogenic granuloma (1.95 per cent). In addition, a number of other odontogenic tumours (1.95 per cent) and non-odontogenic tumours (18.2 per cent) such as fibrosarcoma and squamous cell carcinoma, which are not traditionally associated with the clinical appearance of an epulis, were diagnosed. Of 74 lesions that were previously diagnosed as fibromatous and ossifying epulides, 50 (68 per cent) were reclassified as focal fibrous hyperplasia and 21 (28 per cent) as peripheral odontogenic fibroma (WHO type). The majority of lesions (76 per cent), which were originally classified as acanthomatous epulis, were found to be peripheral ameloblastoma. In addition, three squamous cell carcinomas, two rare odontogenic tumours and two cases of focal fibrous hyperplasia were diagnosed in this classification. It was concluded that, as in man, the term epulis is a clinically descriptive term and that the renal nature of these lesions should be determined histologically.

Fibromatous epulis in dogs and peripheral odontogenic fibroma in human beings: two equivalent lesions

This article compares the clinical and histopathologic features of the peripheral odontogenic fibroma in human beings and the fibromatous epulis in dogs. They are apparently equivalent lesions. Both are odontogenic tumors of limited growth potential that do not recur if adequately excised; both occur in middle and late adulthood of the species concerned. The one difference is that the peripheral odontogenic fibroma is a rare condition, whereas the canine fibromatous epulis is common.

Fordyce's granules of the incisor and molar gingiva in F344 rats

Fordyce's granules were observed in the gingiva of the upper incisor and molar teeth in F344 rats. The data were based on 734 males and 722 females that were used as control and treated animals in 26-week, 65-week, and 2-year studies by the National Toxicology Program. The incidence of Fordyce's granules was markedly different when comparing sex, age, and site of the lesion. Fordyce's granules were very common in the midsagittal gingiva of the upper incisor in males and increased in incidence with age (34.2, 50, and 56.3% in 26-week, 65-week, and 2-year studies, respectively). The granules of the incisor gingiva were rare in females (0,0, and 2.8% in 26-week, 65-week, and 2-year studies, respectively). Fordyce's granules of the molar gingiva were very rare in both sexes and were found only in 9/734 (1.2%) males and in 3/722 (0.4%) females. Only three unilateral granules of the molar were grossly recognized as focal swelling of the gingiva or a white nodule with a huge cyst in the third upper molar. Histologically, Fordyce's granules were arranged as a collection of sebaceous glands unassociated with hair follicles. In addition, the granules of the molar gingiva were associated with cystically dilated ducts filled with sebum. Ultrastructurally, the sebaceous cells were characterized by varying numbers of cytoplasmic lipid droplets and occasional desmosome and hemidesmosome formation. Fordyce's granules previously reported in rats of other strains were also reviewed and compared with those in F344 rats in regard to incidence, location, and age.

Feline oral neoplasia: a ten-year survey

A retrospective histological study was conducted on 371 neoplasms of the oral cavity in cats. Oral neoplasia accounted for 10% of feline neoplasms identified during the survey period. Eighty-nine percent of the oral neoplasms were malignant. Twenty different oral neoplasms were found. The most common were squamous cell carcinoma (61.2%), fibrosarcoma (12.9%), and fibromatous epulis of periodontal ligament origin (7.8%).

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.

Lobular capillary haemangiomas in two calves

Lobular capillary haemangiomas in the gingiva near the mandibular incisor region of two 6-month-old calves are described.

Papillary squamous cell carcinoma in three young dogs

Papillary squamous cell carcinomas were located on the gingiva of 3 young dogs. The tumors locally invaded the soft tissues of each dog, and invaded bone in 2 dogs. Surgical excision was unsuccessful in eliminating 2 of the tumors. Surgery and radiotherapy were effective, and recurrence has not been observed in 39 months in 1 dog, 32 months in a second, and 10 months in a third. Superficially, the oral masses resembled papillomas, which are known to be caused by viruses. Cytopathologic indication of productive infection was not evident, and papillomavirus antigens could not be detected by immunohistochemical methods. Electron microscopy failed to identify viral particles in 2 of the tumors. High and low molecular weight DNA extracts from 2 of the tumors contained no detectable papillomavirus genome when probed under conditions of either high or low stringency by Southern blot hybridization with a cloned canine oral papillomavirus genome.

Classification and behaviour after surgery of canine 'epulides'

Seventy-five surgically excised canine gum neoplasms, which had previously been diagnosed as epulis or ameloblastoma, were reclassified on the basis of their presumed tissue of origin. They included 42 tumours of fibroblastic origin, which contained small foci of odontogenic epithelium and were classified as peripheral odontogenic fibroma, whilst 31 epithelial tumours were classified as basal cell carcinomas arising from the gum epithelium. Two epithelial tumours which apparently arose within the bone of the mandible and were not connected with the surface mucosa were classified as ameloblastomas. Follow-up studies after surgery revealed a recurrence rate of 17 per cent for the odontogenic fibromas and 50 per cent for basal cell carcinomas. Neither of the ameloblastomas, which were initially treated by radical excision, recurred locally and no metastases were detected from any of these tumours.

[Treatment of malignant epulis in dogs]

The successful radiotherapy of malignant epulis in a 12 year-old Dachshund is discussed. Regrowth of the tumour, which was first removed by surgery, was treated with radiotherapy over a period of 36 days in 3 fractions. The total dose was 1800 rads. The lesion healed uneventfully. After 600 days, there was still no new growth but only scar tissue to be seen.

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.

Radiotherapy and hyperthermia in the treatment of fibrosarcomas in the dog

Ten dogs with oral or external nasal fibrosarcoma were treated sequentially with orthovoltage radiation and radiofrequency (RF)-induced hyperthermia. Total radiation doses ranged from 3,200 to 4,800 rad given in 8 to 12 fractions of 400 rad. Immediately after 2 to 4 radiation treatments, hyperthermia was given. Six oral fibrosarcomas were heated to 50 C for 30 sec, using a hand-held RF generator. Four nasomaxillary fibrosarcomas were heated to 43 C for 30 minutes, using a 500-kHz RF generator. Hyperthermia of 50 C resulted in tumor necrosis and infection in 3 dogs and fatal septicemia in 1 dog. Nine of 10 tumors responded to therapy. One year after therapy, 5 dogs were free of disease. Tumor regrowth occurred in 5 dogs. Mean time to tumor regrowth and mean survival time of all dogs were 343 and 398 days, respectively. The results suggested that sequential radiation-hyperthermia is an effective therapeutic regimen for canine fibrosarcoma. It was concluded that this modality not only may be beneficial in the treatment of canine tumors but may be useful for designing new therapeutic approaches to similar tumors in man.

Adamantinoma--histogenesis and differentiation from the periodontal fibromatous epulis and squamous cell carcinoma

Six cases of oral adamantinoma, four in dogs, two in cats, are described. This is a rare tumor which arises from vestigial layers of the dental laminae in the gingiva, particularly of the mandible. Care must be exercised in not confusing this locally aggressive lesion with the much more common squamous cell carcinoma.