# Long-Term Follow-Up after Conservative Surgical Treatment of Odontogenic Myxoma: A Case Report and Literature Review

Authors: Hitoshi Sato; Yuji Kurihara; Sunao Shiogama; Kotaro Saka; Yuya Kurasawa; Masakatsu Itose; Atsutoshi Yaso; Tatsuo Shirota
Journal: Case Reports in Dentistry
 (2019)

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## Abstract

Odontogenic myxoma (OM) is a relatively rare, benign odontogenic tumor with locally aggressive behavior, but it is a nonmetastasizing neoplasm of the jaw bones. Although radical resection with an appropriate surgical margin is recommended, emerging evidence has suggested that a more conservative approach will result in acceptable recurrence rates with less morbidity if careful long-term follow-up is provided. A 56-year-old Japanese man with odontogenic myxoma of the left mandible was conservatively treated by surgical enucleation and curettage because he desired functional and cosmetic preservation. During a follow-up period of 100 months, the patient has remained clinically and radiologically free of recurrence. As far as we can ascertain, 20 reports published after 1990 described 37 patients with mandibular OM that had been treated by conservative surgery. Tumors recurred during a mean follow-up of49.2±42.8 months in 7 (18.9%) patients, and only one of five patients who were followed up for over 100 months developed recurrence. The rate of recurrence decreased from 24.0% to 8.3% when follow-up exceeded 60 months. Although enucleation and curettage have proven effective, the risk of recurrence remains considerable and long-term follow-up is indispensable. More evidence of long-term outcomes after conservative surgery for OM is needed.


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## Body

## 1. Introduction

Odontogenic myxoma (OM) is a benign, locally invasive, aggressive, nonmetastasizing neoplasm of the jaw bones. It is the third most common odontogenic lesion with an annual incidence of ~0.07 new patients per million people [1, 2]. Although OM is a benign tumor, radical treatment is needed because the rate of local recurrence ranges from 10% - 33% [3-5]. Surgical resection with a minimum bone margin of 1 cm has been advocated [6-9], but emerging evidence suggests that a more conservative surgical approach will result in acceptable recurrence rates with less patient morbidity if follow-up can be over the long term [7, 10-12]. However, little has been reported about the actual long-term follow-up of patients with OM after conservative surgery. Here, we describe a mandibular odontogenic myxoma that was treated by conservative surgery and followed up for 100 months thereafter.


## 2. Case Report

### 2.1. Patient Information

A 56-year-old Japanese man was referred from a dental clinic for further examination of a radiolucent finding on the left side of his mandible in January 2010. The patient reported having no symptoms in his mouth including the left mandible area. His medical and dental history was noncontributory. An extraoral examination upon initial presentation revealed unremarkable findings and no complaints of paresthesia. An intraoral examination also confirmed the absence of redness and tender swelling of the left mandibular mucosa (Figure1). Panoramic radiography revealed an extensive multilocular radiolucent area with imprecise borders and a “soap bubble appearance” (Figure 2). Computed tomography showed an approximately 39×19×11mm tumor that extended to the roots of four teeth (#33 - 36; Figures 3(a) and 3(b)). We considered that the odontogenic tumor was benign and an incisional biopsy was performed under local anesthesia. The histopathological findings revealed loosely arranged spindle-shaped cells in a myxoid fibrous stroma, indicating a clinical diagnosis of an odontogenic tumor. Segmental resection of the mandible was planned. The patient was given repeated and careful explanations about the high likelihood of recurrence, but he insisted upon a more conservative approach as he desired functional and cosmetic preservation. Conservative surgery then proceeded under general anesthesia after endodontic treatment of #33 – 36 was completed. The surgery consisted of extracting the second premolar from the left mandible, followed by total enucleation and vigorous curettage of the bone (Figure 4(a)). The surgical specimen (Figure 4(b)) revealed apparently benign, spindled-shaped cells in a loose and abundant mucoid stroma (Figures 5(a) and 5(b)). These findings confirmed the diagnosis of odontogenic myxoma. The immediate postoperative period and wound healing were uneventful. The patient underwent monthly clinical examinations for the first year thereafter, then every two months during the second year. Panoramic X-rays were obtained every three months for the first two years. Annual follow-up for eight years included panoramic X-rays and CT imaging (Figures 6(a) and 6(b), respectively), which showed no clinical or radiological signs of recurrence.Figure 1
Intraoral photography before surgery. The image shows no symptoms such as redness or swelling of mucosa in the mandible.Figure 2
Panoramic dental radiography before surgery. The image shows extensive multilocular radiolucent area with imprecise borders and “soap bubble appearance”.Figure 3
Computed tomography (CT) image before surgery. The axial (a) and coronal (b) CT images show tumor infiltration of cortical bone extending to the inferior mandibular border.
(a)
(b)Figure 4
Surgical procedures and resected specimen. The total enucleation and wide curettage of the surrounding bone (a) and resected specimen (b).
(a)
(b)Figure 5
Pathophysiological findings of stained specimen. Hematoxylin and eosin stain ×100 (a) and ×400 (b) magnification.
(a)
(b)Figure 6
Images of the jaw at 96 months after surgery. The panoramic dental radiograph (a) and computed tomography image (b) show no signs of recurrence.
(a)
(b)


## 2.1. Patient Information

A 56-year-old Japanese man was referred from a dental clinic for further examination of a radiolucent finding on the left side of his mandible in January 2010. The patient reported having no symptoms in his mouth including the left mandible area. His medical and dental history was noncontributory. An extraoral examination upon initial presentation revealed unremarkable findings and no complaints of paresthesia. An intraoral examination also confirmed the absence of redness and tender swelling of the left mandibular mucosa (Figure1). Panoramic radiography revealed an extensive multilocular radiolucent area with imprecise borders and a “soap bubble appearance” (Figure 2). Computed tomography showed an approximately 39×19×11mm tumor that extended to the roots of four teeth (#33 - 36; Figures 3(a) and 3(b)). We considered that the odontogenic tumor was benign and an incisional biopsy was performed under local anesthesia. The histopathological findings revealed loosely arranged spindle-shaped cells in a myxoid fibrous stroma, indicating a clinical diagnosis of an odontogenic tumor. Segmental resection of the mandible was planned. The patient was given repeated and careful explanations about the high likelihood of recurrence, but he insisted upon a more conservative approach as he desired functional and cosmetic preservation. Conservative surgery then proceeded under general anesthesia after endodontic treatment of #33 – 36 was completed. The surgery consisted of extracting the second premolar from the left mandible, followed by total enucleation and vigorous curettage of the bone (Figure 4(a)). The surgical specimen (Figure 4(b)) revealed apparently benign, spindled-shaped cells in a loose and abundant mucoid stroma (Figures 5(a) and 5(b)). These findings confirmed the diagnosis of odontogenic myxoma. The immediate postoperative period and wound healing were uneventful. The patient underwent monthly clinical examinations for the first year thereafter, then every two months during the second year. Panoramic X-rays were obtained every three months for the first two years. Annual follow-up for eight years included panoramic X-rays and CT imaging (Figures 6(a) and 6(b), respectively), which showed no clinical or radiological signs of recurrence.Figure 1
Intraoral photography before surgery. The image shows no symptoms such as redness or swelling of mucosa in the mandible.Figure 2
Panoramic dental radiography before surgery. The image shows extensive multilocular radiolucent area with imprecise borders and “soap bubble appearance”.Figure 3
Computed tomography (CT) image before surgery. The axial (a) and coronal (b) CT images show tumor infiltration of cortical bone extending to the inferior mandibular border.
(a)
(b)Figure 4
Surgical procedures and resected specimen. The total enucleation and wide curettage of the surrounding bone (a) and resected specimen (b).
(a)
(b)Figure 5
Pathophysiological findings of stained specimen. Hematoxylin and eosin stain ×100 (a) and ×400 (b) magnification.
(a)
(b)Figure 6
Images of the jaw at 96 months after surgery. The panoramic dental radiograph (a) and computed tomography image (b) show no signs of recurrence.
(a)
(b)


## 3. Discussion

Odontogenic myxomas are very rare (<10% all odontogenic tumors) benign tumors of the ectomesenchymal and/or mesenchymal origin [13, 14]. They are locally invasive and slow-growing, and their pathological characteristics in the tooth-bearing areas of the mandible and maxilla are well defined [13-17]. The radiographic features are described as those of a multilocular lesion with a “soap bubble” or “spider web” appearance [14-17]. Such lesions are often discovered incidentally during routine dental checkups, and about 60% of patients are in their second or third decade of life [4, 18]. Although the present patient was asymptomatic, panoramic radiography of the left mandible revealed an extensive radiolucent and multilocular area with imprecise borders that extended from the root of tooth #33 to that of tooth #36.The treatment strategy for OM remains controversial. Because OM is locally aggressive and it can potentially cause extensive bony destruction, the treatment of choice seems to be radical surgery such as segmental resection. Indeed, complete surgical removal with curettage and peripheral ostectomy alone seems insufficient since OM is not encapsulated and myxomatous tissue infiltrates adjacent bone [3, 6-9]. Thus, the only initial treatment option for extended OM in principle is surgical resection because of the high risk of recurrence which reportedly ranges from 10% to 33% [4, 5]. In addition, recurrence rates can reach 25% after simple enucleation and curettage alone [19, 20]. On the other hand, some reports described that the choice of current recommended therapy depends on the size of the lesion and its nature and behavior between curettage and radical excision [3, 7]. In the present case, CT had shown that the tumor included the #33 - #36 apex and extended to the inferior border of the mandible. Therefore, radical resection such as block resection for mandible was strongly recommended. However, the patient rejected this strategy because he desired functional and cosmetic preservation, and in fact, conservative treatment with enucleation, curettage, and marginal resection would confer several advantages over the radical approach. It is substantially less invasive, it can be surgically implemented via an intraoral approach, and it offers the possibility of preserved nerve function and aesthetics and a shorter stay in the hospital. Recent evidence suggests that a more conservative approach will result in acceptable recurrence rates with less morbidity to patients if long-term follow-up is provided [7, 10-12]. Table 1 describes 20 reports of 37 patients with that was treated by conservative surgery [4, 6, 7, 10, 11, 17, 18, 21-33]. The mean age of the patients was 27.0±15.2, and 20 (54%) were female. The tumors in almost all of them were managed by enucleation and curettage and recurred in 7 (18.9%). One and six of the procedures with recurrence had undergone marginal resection and enucleation with curettage, respectively. The patients were followed up for a mean of 49.2±42.9 (range, 2 – 180) months. Including the present patient, only five have been followed up for over 100 months and the tumor recurred in one of them. The recurrence rate among all patients who were treated by conservative surgery was 19.0%. This rate is relatively lower than that previously described [19, 20]. Furthermore, our investigation of the literature indicated that the rate of recurrence decreases from 24.0% to 8.3% when the follow-up period exceeds 60 months.Table 1
Clinical reports of mandibular odontogenic myxoma published after 1990.
No.
Author
Year
Age
Sex
Follow-up period (months)
Treatment
Recurrence
Size (mm)
1
Oliveira et al. [21]
2018
9
F
6
E/C
None
NA
2
Albanese et al. [22]
2012
25
F
6
E
None
21.2×47.6
3
Mauro et al. [23]
2012
6
M
6
E/C
None
NA
4
Subramaniam et al. [7]
2016
16
—
7
M
None
NA
5
Shivashankara et al. [24]
2017
13
M
12
E/N
None
40×20
6
Subramaniam et al. [7]
2016
18
—
12
E
None
NA
7
Miranda Rius et al. [25]
2013
55
M
12
E/C
None
33×28
8
Hammad et al. [26]
2016
45
F
13
M
None
50×30
9
Francisco et al. [27]
2017
9
F
14
E/C
Recurrence
NA
10
Francisco et al. [27]
2017
12
F
16
E/C
Recurrence
NA
11
Sumi et al. [28]
2000
48
M
22
E/C
None
70×25×15
12
Mittal et al. [29]
2016
48
F
24
E/C
Recurrence
25×20
13
Lin and Basile [30]
2010
25
F
24
E
None
NA
14
Lo Muzio et al. [4]
1996
21
M
24
E/C
None
NA
15
Lo Muzio et al. [4]
1996
28
M
24
E/C
Recurrence
NA
16
Bucci et al. [31]
1993
28
M
24
E/C
None
43×40
17
Francisco et al. [27]
2017
7
F
26
E/C
None
NA
18
Francisco et al. [27]
2017
15
F
27
E/C
Recurrence
NA
19
Lo Muzio et al. [4]
1996
16
F
31
E/C
None
NA
20
Francisco et al. [27]
2017
30
F
34
E/C
None
NA
21
Boffano et al. [11]
2011
38
M
38
E/C
None
25
22
Boffano et al. [11]
2011
42
F
40
E/C
None
30
23
Boffano et al. [11]
2011
20
M
42
E/C
None
20
24
Rajasekhar et al. [32]
2008
17
F
48
M
None
70×30
25
Lo Muzio et al. [4]
1996
22
F
48
E/C
Recurrence
NA
26
Takahashi et al. [6]
2018
37
F
73
E/C
None
40×19×12
27
Chaudhary et al. [33]
2015
25
F
84
E/C/M
None
NA
28
Li et al. [18]
2006
7
M
84
E/C
None
NA
29
Li et al. [18]
2006
32
M
84
E/C
None
NA
30
Lo Muzio et al. [4]
1996
65
F
84
E/C
None
NA
31
Francisco et al. [27]
2017
17
M
85
E/C
None
NA
32
Francisco et al. [27]
2017
11
F
98
E/C
None
NA
33
Present case
56
M
100
E/C
None
39×19×11
34
Francisco et al. [27]
2017
27
F
117
E/C
None
NA
35
Kawase-Koga et al. [10]
2014
40
M
120
E/C
None
40×30×15
36
Li et al. [18]
2006
37
M
132
C
None
NA
37
Kansy et al. [17]
2012
33
F
180
M
Recurrence
NA
Abbreviations: M: male, F: female, E: enucleation, C: curettage, M: marginal resection, and NA: not available.The main reason for recurrence is thought to be incomplete removal rather than the intrinsic biological behavior of the OM [34]. Although the tendency is towards a more conservative surgical approach for children and a more radical approach for adults, Kansy et al. does not support this management strategy because the recurrence rates between enucleation and segmental resection are similar [17]. Tumor size has recently been considered to be a factor in the choice of a radical or more conservative surgical approach [4, 10, 11]. Conservative surgical procedures such as enucleation and curettage are recommended when the diameter of OM is <3 cm, whereas a radical approach such as segmental resection with immediate reconstruction is preferred when patients have larger tumors [11]. The conservative surgical recommendation is to enucleate a lesion with wide curettage of normal tissue or a generous amount of apparently intact tissue or even marginal resection of the mandible [12]. This approach has the advantage of preserving vital structures and maintaining oral function, and it could be applied to treat OM that recur after simple surgery [12]. However, one patient who developed recurrent OM 15 years after the initial procedure including tumor resection with the preservation of mandibular continuity has been described [17]. More radical surgery is inevitable for a large number of patients due to a tendency towards more extensive OM with significant destruction of key structures [17, 27]. Moreover, the rate of OM recurrence remains vague because few reports described long-term follow-up after conservative surgery. Thus, more evidence about long-term outcomes after conservative surgical treatment of OM is needed.


## 4. Conclusions

A conservative surgical approach comprising enucleation and curettage can be effective for OM management. Recurrence rates decreased from 24.0% to 8.3% among patients who were treated with conservative surgery and followed up for over 60 months. The risk of recurrence is likely to be considerable, and long-term follow-up is indispensable for the conservative management of OM.



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