Peripheral Squamous Odontogenic Tumor: A Rare Case Report
Bal Reddy P, Rajinikanth M, Shyam NDVN, Anil K.
Squamous odontogenic tumor is a benign, locally infiltrative, intraosseous tumor composed of well-differentiated squamous epithelium in the background of fibrous stroma. It was first described in 1975 by Pullon et al and is thought to arise from the rests of Malassez in the periodontal ligament or in the cases of peripheral squamous odontogenic tumor, from gingival surface epithelium and remnants of dental lamina. Squamous odontogenic tumors have shown very little tendency for aggressive clinical behaviour and virtually no recurrences have been reported following curettage and peripheral ostectomy. In addition, only one intra-osseous case has been reported as being associated with a malignant variant. There are two reports of peripheral presentations. We present a case in a 17 year old female patient who presented with a peripheral swelling in the chin region, which was excised and diagnosed as peripheral squamous odontogenic tumor.
Key Words: Squamous; Odontogenic tumor; Oral; Jaw Neoplasms; Infiltrative.
Bal Reddy P, Rajinikanth M, Shyam NDVN, Anil K. Peripheral Squamous Odontogenic Tumor: A Rare Case Report. International Journal of Oral & Maxillofacial Pathology; 2011:2(2):28-30. ©International Journal of Oral and Maxillofacial Pathology. Published by Publishing Division, Celesta Software Private Limited. All Rights Reserved.
Received on: 15/12/2010 Accepted on: 29/05/2011
Squamous odontogenic tumour is a rare, benign but locally infiltrative epithelial tumour. To date, only 42 central squamous odontogenic tumor cases have been reported in the literature. There are 2 reports of peripheral presentations.1 There are no reports of peripheral squamous odontogenic tumor showing malignant changes. The particularly aggressive evolution of this case in a young patient led practitioners to revise the histological diagnosis, treatment and prognosis.
A 17 year old female patient reported to Department of Oral Surgery, Government Dental College and Hospital, Hyderabad, with a complaint of swelling in the chin region from past 3 months. Patient gave a history of accident and minor injury in the same region which was associated with loss of 31 tooth. A local dentist performed root canal treatment in relation to 41 tooth, which was later extracted as she developed pain. The patient noticed a small swelling in the lower sulcus region, which subsequently increased to the present size. On extra-oral examination there was a mass of 5x3cm in the chin region which was tender on palpation. Skin over the mass was fixed, with few cutaneous eruptions on it. On intra-oral examination there was obliteration of the labial vestibule. Intraoral periapical and orthopantomographic radiographs did not
reveal any changes in relation to the mass. Differential diagnosis includes peripheral odontogenic tumor and squamous cell carcinoma of mandible. Under General anaesthesia, we performed a wide excision of the soft tissue mass, as there were no bony changes seen even intra-operatively.
The histopathology showed numerous islands of proliferative squamous epithelium dispersed uniformly in a connective tissue stroma (Fig 1). The islands were easily recognized, sharply demarcated from the surrounding stroma by a flattened layer of cells at their periphery. The central areas of the islands showed areas of keratinisation and cystic formation (Fig 2). Towards the periphery there were few cells showing hyperchromatism, pleomorphism and abnormal mitosis. The final diagnosis was peripheral squamous odontogenic tumor.
Squamous odontogenic tumor is probably the rarest of all the odontogenic tumors. From the limited number of published cases, however, it is still possible to draw some conclusion regarding the usual demographic, clinical and radiographic presentation of the tumor. There is no apparent predilection for occurrence in either the mandible or maxilla. However, lesions of the maxilla tend to occur more often in the anterior regions, while mandibular cases are more often found in the posterior areas. In our case the lesion was present in the
anterior mandible and this site is unfamiliar to the other lesions in the literature. A wide age range has been reported without clustering of a majority of cases into a characteristic age of occurrence. Males and females appear to be equally affected.2-4
Figure 1: Photomicrograph (10X) showing numerous islands of proliferative squamous epithelium dispersed uniformly in a fibrous connective tissue stroma.
Figure 2: Photomicrograph (40X) showing the epithelium in these rounded islands.
In their 1996 review of previously reported cases, Philipsen et al5 noted that 10 of 35 cases of squamous odontogenic tumor were multicentric. In our case, there were no radiological changes seen in the underlying bone. Lesions of squamous odontogenic tumor are only locally destructive, however, tumors of the maxilla tend to behave more aggressively because of the regional anatomy and the challenges it poses for the surgeon. In our case, the lesion occurred in the mandibular chin region, but still it behaved aggressively.
The squamous odontogenic tumor generally produces a readily recognizable pattern on histologic examination. The tumor consists of numerous islands of proliferative squamous epithelium dispersed uniformly in a connective tissue stroma. The islands are numerous and easily recognized, being sharply demarcated from the surrounding stroma by a flattened layer of cells at their periphery. They tend to vary somewhat in shape, but as a rule, round to oval islands are always seen. The epithelium in these rounded islands often shows a swirling or “whirlpool” pattern to the central squamous cells. Areas of cystic change centrally within the epithelial islands are also a frequent finding and keratinization of the central cells may be present too.3 In light of the relatively few reported cases, there are no consistently recorded clinical features of squamous odontogenic tumor and there is no gender or site predilection.2 Diagnosis is based on recognition of the histopathologic features of squamous odontogenic tumor to obviate possible misdiagnosis.
Misdiagnosis as peripheral ameloblastoma can also occurs occasionally.4 In that lesion it is possible to observe palisaded columnar ameloblastic cells lining the epithelial islands and a stellate reticulum configuration of the central portion of the islands.
As there may be some degree of pleomorphism, hyperchromatism and occasionally an increased number of mitotic figures, these lesions have mistakenly been diagnosed as squamous cell carcinoma by some pathologists unfamiliar with the neoplasm.5 In squamous cell carcinoma, the epithelial connective tissue interface is ruptured, numerous epithelial islands exhibiting dysplastic features and surrounded by chronic inflammatory cells can be seen. But in our case such features were not visible.
Ameloblastic carcinoma shows irregular masses with interdigitating cords of epithelial cells having palisading pattern around the periphery. The tissue in the centre of the cellular islands is composed of stellate reticulum. Other areas show islands of keratinizing well-differentiated squamous cell carcinoma infiltrating the adjacent bone. In our case there was no such palisading pattern of epithelial cells or infiltration into the adjacent bone was noted. Thus ameloblastic carcinoma was ruled out.6-8
In our lesion, semi-serial sections revealed a typical pattern of squamous odontogenic tumor in most parts. Thus, the most appropriate interpretation for this lesion as peripheral squamous odontogenic tumor was made.
1. Dr. Bal Reddy P, Professor, Department of Oral Surgery, Govt Dental College and Hospital, Hyderabad, Andhra Pradesh, India. 2. Dr. Rajini Kanth M, Associate Professor, Department of Oral and Maxillofacial Pathology, G Pulla Raddy Dental College and Hospital, Kurnool, Andhra Pradesh, India. 3. Dr. Shyam NDVN, Associate Professor, Department of Oral and Maxillofacial Pathology, Govt Dental College and Hospital, Hyderabad, Andhra Pradesh, India. 4. Dr. Anil K, Senior Lecturer, Army College of Dental Sciences, Hyderabad, Andhra Pradesh, India.
All Staff Members in the Department of Oral & Maxillofacial Pathology, G Pulla Raddy Dental College and Hospital, Kurnool.
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Dr. Rajinikanth M.,
G Pulla Reddy Dental College & Hospital,
Kurnool, Andhra Pradesh, India.
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