Desmoplastic Ameloblastoma—A Case Report

ABSTRACT

Desmoplastic ameloblastoma (DA) is a rare variant of conventional ameloblastoma. It accounts for only 4%–13% of all ameloblastomas. DA was included in the World Health Organization Classification of Head and Neck Tumors (WHO-2005) as a variant of ameloblastoma with specific clinical, imaging, and histological features. The desmoplastic variant of ameloblastoma usually appears in the anterior and premolar regions as a mixed radiolucent and radiopaque lesion, sometimes resembling a benign fibro-osseous lesion.Ameloblastoma is a locally aggressive tumor that may cause recurrence and in rare cases, malignant transformation with repeated postsurgical recurrences. In this paper, we present a case of a 28-year-old female with swelling in the left upper jaw, a biopsy of which turned out to be DA.

INTRODUCTION

Desmoplastic ameloblastoma (DA) was first described by Eversole et al. in 1984 as a new type of ameloblastoma with a unique histological pattern characterized by the presence of islands of ameloblastic columnar cells surrounding spindle-shaped stellate reticulum-like cells in a stroma with marked desmoplasia.[1] The desmoplastic variant of ameloblastoma usually appears in the anterior and premolar regions as a mixed radiolucent and radiopaque lesion, sometimes resembling a benign fibro-osseous lesion.[2,3] The main histological types of ameloblastoma are the follicular and plexiform patterns. DA is one of the other less common histological variants.[4] The desmoplastic variant of ameloblastoma usually appears in the anterior and premolar regions as a mixed radiolucent and radiopaque lesion, sometimes resembling a benign fibro-osseous lesion. A differential diagnosis between the osteoplastic variant and fibro-osseous lesions such as fibrous dysplasia or ossifying fibroma can be very difficult. Different methods of treatment have been described, but most authors agree that the management of solid ameloblastoma should be radical and primary curative. Conservative therapy, such as enucleation, is associated with a high rate of recurrences.[5]

CASE REPORT

A 28-year-old female with non-contributory cultural, social, and medical histories presented to the outpatient department of Teeth Zone Dental clinic, Salem, Tamil Nadu, India. The patient had a history of swelling in the left upper jaw for more than three years; it was slow growing and painless. On clinical examination 5 × 5 cm smooth swelling was seen on the left premolar area of the jaw. It was hard on consistency, which was painless and uneventful. Teeth 24 and 25 were immobile; there was no displacement of the roots of teeth observed. A coronal view of CT revealed a poorly defined, mixed, radiolucent-radiopaque image, suggesting a benign fibro-osseous lesion [Figure 1]. No cervical lymph node was palpable. The patient was subjected to an incisional biopsy and was approached by a sub-labial incision. A small piece of about 1 cm was removed from the swelling by gauge and mallet and sent for histopathological examination to the Department of Oral Pathology and Microbiology, Vivekanandha Dental College for Women, Tiruchengode.

Figure 1.

CT imaging showing soap bubble appearance with a displacement of 24 and 25

Histopathological examinations showed epithelial islands surrounded by dense connective tissue stroma, resembling odontogenic epithelium consisting of peripherally arranged cuboidal to a few columnar cells with hyperchromatic nuclei and centrally placed squamous cells. The surrounding stroma is moderately cellular with abundant thick collagen fibers compressing the odontogenic islands. The periphery of the stroma consists of metaplastic bone rimmed with active osteoblasts. Hence, the histopathology was reported as DA [Figures 2-4]. It was decided to remove the tumor in total. The whole mass was removed after obtaining informed and written consent from the patient and sent for histopathological examination, and the report came as DA and the margins were free.

Figure 2.

Odontogenic islands surrounded by abundant thick collagen fibers compressing the odontogenic islands (H and E stain)

Figure 4.

Periphery of the stroma showing osseous metaplasia with active osteoblast rimming (H and E stain)

Figure 3.

Odontogenic epithelium with peripherally arranged cuboidal to few columnar cells with hyperchromatic nuclei and centrally placed squamous cells (H and E stain)

DISCUSSION

DA is a rare variant of ameloblastoma, which is characterized by marked stromal desmoplasia. This tumor is most commonly found in the fourth and fifth decades of life, with no sex predilection.[6] Usually, DA is smaller than other types of ameloblastoma, but if neglected, it can be very extensive and destructive, requiring wide excision. More frequently, it occurs in the anterior part of the jaws, and there is no difference in prevalence between the maxilla and the mandible. The main clinical symptom is a painless swelling with a buccal expansion of the mass and tooth displacement.[7] In a recent article, Effiom and Odukoya[8] stated that multilocular radiolucency is the predominant radiographic presentation of the desmoplastic variant of DA. In contrast, the variant with osteoplasia presented a mixed radiolucent and radiopaque appearance, thereby mimicking a fibro-osseous lesion. In 1984, Eversole et al. first described “desmoplastic ameloblastoma.” Histologically, DA consists of an abundant and excessive stromal collagenization or desmoplasia in which irregularly shaped islands of odontogenic epithelium are scattered. Waldron and El-Mofty introduced the term “hybrid lesions” to describe the conditions in which DA was located adjacent to follicular or plexiform ameloblastoma. Wakoh et al.[9] presented a case of a patient demonstrating follicular-type ameloblastoma with desmoplasia, in which radiological findings suggested the coexistence of a fibro-osseous lesion with a solitary cystic lesion and proposed it to be a hybrid follicular/DA. DA is rare, accounting for approximately 4%–13% of ameloblastomas. Our case of a 28-year-old female with a three-year history of swelling in the left upper jaw whose biopsy turned out to be DA, for which the patient was subjected to an inferior partial maxillectomy, and the margins were confirmed free of the disease. In this case, we learned that clinicians should suspect DA if a patient attends with complaints of swelling in and around the premolar region.

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Conflicts of Interest

There are no conflicts of interest.