Clinicopathological study and treatment outcomes of 121 cases of ameloblastomas

Abstract

The aim of this paper is to evaluate the clinical, radiographic, and histopathological findings and treatment modalities in all cases of ameloblastomas treated at the Sao Paulo Cancer Hospital, between 1953 and 2003. 121 case reports were retrieved from the medical files. Data were reviewed and statistical analysis was performed using Kaplan–Meyer method and Cox proportional risk model. The patients’ age ranged from 2 to 82 years (mean 33.2 years), with a slight female prevalence. Most cases were located in the posterior mandible (80%). Radiographically, 60% showed a multilocular pattern. 113 casees were solid ameloblastomas, and plexiforme subtype was the most common. Solid tumours were treated by wide resection, curettage and criosurgery, or curettage alone, and unicystic tumours by curettage and/or cryotherapy. The global mean recurrence rate was 22%, with a mean follow-up of 9.7 years. The ameloblastomas were predominantly solid, affecting the posterior mandible. Important factors for outcome were radiographically multilocular lesions, the presence of ruptured basal cortical bone and histologically follicular tumours.

Ameloblastomas comprise 13–58% of all odontogenic tumours, and were first described by Cusack in 1827 and detailed by Broca in 1868 . The WHO classifies ameloblastomas as benign odontogenic tumours formed by odontogenic epithelium with fibrous mature stroma, but without odontogenic ectomesenchime .

Solid/multicystic; unicystic and peripheral variants, with distinctive clinical, demographic and biological features are well-established . Solid ameloblastomas are the most frequent, characterized by a slow but infiltrative growth pattern and locally aggressive, occurring mainly on the posterior mandible of young adults (25–36 years). Radiographically ameloblastomas are uni- or multilocular osteolytic lesions, frequently showing cortical expansion. Microscopically, the follicular and plexiform patterns are the most common, and other subtypes include acantomatous, desmoplastic, granular and basal. It is common to find more than one histological variant in the same tumour . Characteristically, polarized cells that resemble ameloblasts surround tumour cells, nests and cystic cavities.

The term unicystic ameloblastoma derives from the macro and microscopic appearances. The lesion is essentially a well-defined single cavity lined with ameloblastomatous epithelium, and three variants are found: luminal, intraluminal and mural .

Treatment of ameloblastoma is controversial. Unicystic ameloblastomas are usually treated conservatively with curettage and cryosurgery. There is discussion in the literature about different treatment approaches for solid ameloblastomas .

The aim of this study was to evaluate the clinical, radiographic, and histopathological findings and treatment modalities of 121 cases of ameloblastomas over 50 years at a single institution.

Material and methods

The notes of all cases diagnosed as ameloblastomas between 1953 and 2003 were retrieved from the hospital files. Clinical, radiographical, treatment and follow-up information were obtained from the patients’ records. This is a long-term retrospective study so there are no treatment protocols because they varied according to the department in which the patient was treated.

All hematoxylin–eosin stained slides were reviewed and the tumours classified according to 2005 WHO criteria . Cases without enough data or pathological specimens (slides or parafin block) were excluded from the study; 121 cases were included.

Follow-up was calculated from the date of the first treatment to the date of the last available assessment. The Kaplan–Meyer method was used to assess the probability of recurrence, and the log-rank test was used to compare the recurrence-free survival curves. Statistical assessment of the clinical and histopathologic variables was carried out by a multivariate regression analysis Cox’s proportional risk model.

Results

Most patients were Caucasians (72%), with a slight female predominance (53%), and ages ranged from 2 to 82 years (mean 33.2 years). The clinical size of the lesions ranged from 1.5 to 25 cm, with a mean of 5.5 cm. The main complaints were swelling in the involved area (83%) and/or pain (33%). Most cases were located in the posterior region of the mandible (80%). Table 1 shows further details of the distribution of all cases studied. Most patients were treated initially at the A.C. Camargo Hospital, but 31 cases (26%) had been treated elsewhere with bone curettage (22 cases), segmental resection (6 cases) and marsupialization (3 cases).

Table 1
Site distribution of 121 cases of ameloblastoma.
N %
Maxilla 12 9.9
Right – posterior region 2 1.6
Left – posterior region 9 7.4
Anterior maxilla 1 0.8
Mandible 108 89.2
Right – posterior region 50 41.3
Left – posterior region 47 38.9
Anterior mandible 11 9.1
Peripheral 1 0.8
Total 121 100.0

113 cases were classified as solid (93%), 7 (6%) as unicystic and 1 as peripheral. Regarding the solid tumours, most of them (62%) were radiographically multilocular; 65% showed expansion and 25% discontinuity of the vestibular and/or lingual bone plate. The basal plate bone presented expansion in 40% of the cases and discontinuity in 13%. Histologically, most cases were classified as plexiform (53%) or follicular (34%). Other histological subtypes (13%) identified were acantomathous (7 cases), granular (5 cases), desmoplastic (2 cases) and haemangiomatous (1 case). Regarding the treatment of the 113 solid ameloblastomas: 47 cases were treated with segmental resection, 47 with bone curettage followed by cryotherapy, and 19 cases with bone curettage only.

Diagnosis of unicystic ameloblastoma was confirmed in seven cases, considering the image examinations, macroscopic and histologic findings. The mean age was 35 years; five cases affecting women. All cases showed unilocular images and 4 were of the mural histological variant. All cases were treated conservatively by curettage or curettage and cryotherapy. The only patient affected by an extra-osseous lesion was a 29-year-old Caucasian man. The lesion (3 cm in size) was located on the left mandibular alveolar edge and it was treated by enucleation. The histological aspect of this case was predominantly follicular.

The mean follow-up time was 9.7 years and 27 patients presented recurrences, 25 of the 113 (22%) with solid ameloblastomas and 2 of 7 (29%) with unicystic lesions. Extra-osseous recurrences occurred in four solid ameloblastomas. The two unicystic cases that recurred were of the mural subtype; one had been treated with curettage associated with cryotherapy, and the other with curettage only. Table 2 shows the data for recurrences of solid ameloblastomas. The χ 2 test indicated that there were no significant statistical differences between recurrences and type of treatment performed.

Table 2
Recurrences of 113 cases of solid ameloblastomas according to the treatment modality. There were no statistical differences between treatment modalities and recurrences. * .
Treatment N total N with recurrence % of recurrence
Segmental resection 47 8 17.0
Bone curettage + cryoterapy 47 14 29.8
Bone curettage 19 3 15.8
Total 113 25 22.1

* χ 2 test: P = 0.252.

Table 3 shows the main data for solid ameloblastomas cases, as well as the results of Cox’s univariate regression for analysis of the clinical variables correlated with recurrences. Of the clinical variables, only the radiographic pattern and the basal cortical bone status were statistically significant. Patients with radiographically multilocular lesions had 3.02 times more chance of recurrences than patients with unilocular lesions ( Fig. 1 ). Patients who presented only expanded basal cortical bone had 0.24 times more chance of recurrence than those with ruptured basal cortical bone. Patients with preserved basal cortical bone had 0.15 times more chance of recurrence than patients with ruptured basal cortical bone. This parameter was analysed only in mandibular cases.

Table 3
Main findings of 113 cases of solid ameloblastomas and univariate analysis.
Variable Category N total N (%) with recurrence HR CI 95% P
Age (years) <18 16 4 (25.0) 1.00
18–32 50 15 (30.0) 1.37 0.45–4.16 0.581
>32 47 6 (12.8) 0.45 0.13–1.60 0.216
Ethnic Afro Brazilian 27 6 (22.2) 1.00
Caucasian 86 19 (23.2) 0.90 0.36–2.28 0.830
Gender Male 54 10 (18.5) 1.00
Female 59 15 (25.4) 1.94 0.85–4.46 0.117
Time of complaining (months) ≤12 58 13 (22.4) 1.00
>12 47 10 (21.3) 1.04 0.45–2.45 0.923
Clinical tumour size (cm) <5 35 6 (17.1) 1.00
5–10 39 12 (30.8) 1.97 0.73–5.34 0.183
>10 6 0 (0.0)
Tumour site Mandible 102 24 (23.5) 1.00
Maxilla 11 1 (9.1) 0.35 0.05–2.56 0.299
Soft tissue infiltration No 67 13 (19.4) 1.00
Yes 41 11 (26.8) 1.30 0.57–2.97 0.535
Previous treatment No 84 14 (16.7) 1.00
Yes 29 11 (37.9) 2.04 0.90–4.59 0.086
Treatment Segmental resection 47 8 (17.0) 1.00
Bone curettage + cryotherapy 47 14 (29.8) 1.91 0.77–4.75 0.161
Bone curettage 19 3 (15.8) 0.94 0.24–3.65 0.932
Radiographic pattern Unilocular 38 4 (10.5) 1.00
Multilocular 62 18 (29.0) 3.02 1.01–9.04 0.048
Cortical bone V e L(P) Torn 28 8 (28.6) 1.00
Expanded 65 13 (20.0) 0.57 0.23–1.40 0.224
Preserved 7 0 (0.0)
Basal cortical bone Torn 11 6 (54.5) 1.00
Expanded 34 7 (20.6) 0.24 0.08–0.74 0.013
Preserved 40 7 (17.5) 0.15 0.05–0.49 0.002
Pathologic fracture No 101 23 (22.8) 1.00
Yes 4 0 (0.0)
Main histopathological pattern Follicular 38 12 (31.6) 1.00
Plexiform 60 8 (13.3) 0.31 0.12–0.80 0.015
Others * 15 5 (33.3) 0.90 0.32–2.56 0.844
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Feb 8, 2018 | Posted by in Oral and Maxillofacial Surgery | Comments Off on Clinicopathological study and treatment outcomes of 121 cases of ameloblastomas
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