METHODOLOGY Open Access
Piezoelectric-assisted removal of a benign fibrous
histiocytoma of the mandible: An innovative
technique for prevention of dentoalveolar nerve
injury
Maximilian EH Wagner1†, Majeed Rana1*†, Wolfgang Traenkenschuh2, Horst Kokemueller1, André M Eckardt1 and
Nils-Claudius Gellrich1
Abstract
In this article, we present our experience with a piezoelectric-assisted surgical device by resection of a benign
fibrous histiocytoma of the mandible.
A 41 year-old male was admitted to our hospital because of slowly progressive right buccal swelling. After further
radiographic diagnosis surgical removal of the yellowish-white mass was performed. Histologic analysis showed
proliferating histiocytic cells with foamy, granular cytoplasm and no signs of malignancy. The tumor was positive
for CD68 and vimentin in immunohistochemical staining. Therefore the tumor was diagnosed as primary benign
fibrous histiocytoma. This work provides a new treatment device for benign mandibular tumour disease. By using a
novel piezoelectric-assisted cutting device, protection of the dentoalveolar nerve could be achieved.
Keywords: Piezosurgery, benign fibrous histiocytoma, mandibular tumor, dentoalveolar nerve, atraumatic bone
surgery
Background
According to the WHO histological classification of
tumors, primary benign fibrous histiocytoma (BFH) of
bone is defined as a benign lesion composed of spindle-
shaped fibroblasts, arranged in a storiform pattern, with
a variable admixture of small, multinucleated osteoclast-
like giant cells. Foamy cells (xanthoma), chronic inflam-
matory cells, stromal haemorrhages and haemosiderin
pigment are also commonly present [1]. According to
this classification, there are less than 100 reported cases
of BFH worldwide and only six reported cases in the
mandible [2-7]. It is usually found in long bones, espe-
cially femur and tibia, and the pelvic bone, but may
occur in virtually any bone. However, the precise
removal especially in close vicinity to nerval structures
is challenging. In our case resection of a mandibular
tumor by preventing injury to the dentoalveolar nerve is
difficult.
The presented case enlarges the indications for the use
of ultrasonic devices in tumor surgery and thus empha-
sizes the beneficial effects of this technique in bone cut-
ting close to nerval structures.
Materials and methods
A 41-year old Caucasian man was referred to our clinic
for evaluation of a slowly progressive swelling of his
right mandible. A panoramic radiograph (Figure 1)
showed a well-demarcated multilocular radiolucent
lesion with a reactive hyperostotic border in the right
mandibular molar region. No other symptoms had been
noted before.
A computed tomography (CT) scan was obtained,
which showed a heterogeneous soft-tissue mass (Figure
2). There was vertical expansion more prominent of the
lingual side with thinning of the cortex and two small
spots of cortical destruction. No lymph node involve-
ment was observed. A magnetic resonance imaging
* Correspondence: rana.majeed@mh-hannover.de
† Contributed equally
1Department of Cranio-Maxillo-Facial Surgery, Hannover Medical School,
Germany
Full list of author information is available at the end of the article
Wagner et al. Head & Face Medicine 2011, 7:20
http://www.head-face-med.com/content/7/1/20
HEAD & FACE MEDICINE
© 2011 Wagner et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons
Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in
any medium, provided the original work is properly cited.
(MRI) scan was performed to exclude the presence of a
haemangioma prior to osseous biopsy (Figure 2).
Histopathological examination (Figure 3, 4) and
immunohistochemical staining (Figure 5, 6) confirmed
the diagnosis of primary benign fibrous histiocytoma.
The patient was treated definitely via an extraoral
submandibular approach (Figure 7). Simple cyst-like
excochleation of the tumor in one piece was not possi-
ble due to different consistencies of the lesion. Rub-
ber-like soft tissue parts of the tumor could be
removed by curettage and excision, while bone-like
hard tissue parts had to be removed using a bone drill.
To prevent any nerve damage, bone-like hard tissue
parts in the vicinity of the dentoalveolar nerve were
removed exclusively by using the piezoelectric device
(Figure 8). Despite the cortical destruction of lingual
and buccal bone, the surrounding tissue was not
affected. The lower rim of the right mandible could be
preserved, stabilized with a osteosynthesis plate for
fracture prevention. In order to achieve complete
resection of the tumor, the teeth 46 and 47 were
extracted and neurolysis of the inferior alveolar nerve
was performed (Figure 9).
The neurological analysis was performed bilaterally. It
was used to evaluate nerve dysfunctions. The skin of the
mental region, upper and lower lip were checked using
a cotton test for touch sensation, a pinprick test using a
needle for sharp pain and a blunt instrument for testing
pressure. Additionally, a two point discrimination test
was executed on these regions. The same procedure was
accomplished for the lower lip and the mental nerve
skin region. The results were recorded on a score that
ranges between 0 and 13, with 13 being the worst neu-
rological score. The neurological score was assessed at 4
points in time: on the 1st (T1 = 9), the 10th (T2 = 7),
the 22nd (T3 = 3), the 184th (T4 = 1) postoperative day.
Figure 1 Preoperative panoramic radiograph.
Figure 2 Preoperative CT and MRI scans showing the heterogeneous lesion in the right mandible with no vascular signs.
Figure 3 Histopathological examination of the obtained tissue
showing spindle-shaped fibroblasts, arranged in a storiform
pattern (hematoxylin-eosin-staining, magnification 25×).
Wagner et al. Head & Face Medicine 2011, 7:20
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Piezosurgery® (Mectron®-Germany, Cologne, Ger-
many) is an ultrasound device introduced in medical
practice in 1988 for different procedures in application
to hard tissues, including periodontal surgery, periapical
surgery,[8,9] the removal of impacted teeth, implant sur-
gery for facilitating bone ridge expansion or in bone
regeneration techniques,[10,11] inferior dental nerve
lateralization and transpositioning. Furthermore ultra-
sound has lately been used for osteotomies as well as
for dental implant bone preparation and thus presents
an additional option for cutting bone beside the classic
osteotomy techniques using rotating burs or oscillating
saws [12]. With this new option, the bone is cut almost
without pressure through piezoelectrically induced oscil-
lations. Micro-movements of 60-200 μm ensure that
only the mineralized hard tissue is cut. The frequency of
the oscillations applied in osteotomies lies between 22
and 29 kHz. This makes it possible to reliably prevent
damage to soft tissue and nerve tissue during an osteot-
omy [10,13]. Trauma to these types of tissue is only
likely to occur at frequencies of 50 kHz or more [14,15].
Discussion
A primary benign fibrous histiocytoma in the mandible
is extremely rare with only six reported cases in the lit-
erature [2-7].
The etiology of BFH is not yet clear. It may be a neo-
plasm consisting of fibroblasts and histiocytic-like cells
[16] or a regression phenomenon of giant cells tumors
[6]. BFH is mainly found in the pelvic bone, femur and
Figure 4 While in other parts of the specimen proliferating
histiocytic cells with foamy, granular cytoplasm and no signs
of malignancy dominate (hematoxylin-eosin-staining,
magnification 100×).
Figure 5 Immunohistochemical staining positive for CD68
(magnification 100×).
Figure 6 mmunohistochemival staininga also positive for
vimentin (magnification 100×), and negative for sm-actin,
desmin, cytokeratin, S-100 protein or CD-56.
Figure 7 Intraoperative image of the original mandible.
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tibia. Patients often report a history of pain or swelling
over a long period of time, sometimes years. A sclerotic
rim around the osteolytic defect is common [17].
The histologic appearance of BFH is identical to non-
ossifying fibroma, making a clinical radiographic evalua-
tion indispensable. The non-ossifying fibroma typically
occurs during growth. BFH on the other hand is found
in older patients, presenting with swelling or pain but
usually no presence of complicating fractures. Non-ossi-
fying fibroma is limited to the metaphysis of mainly the
lower extremities, whereas BFH is found in the epi- or
diaphysis or in flat bones [17].
To distinguish BFH from giant cell tumors can be
challenging. On the one hand giant cells can be numer-
ous in BFH, even if the mononuclear cell component is
more spindled and associated with collagen formation
[18]. On the other hand focal or extended fibrous tissue
with lipid-bearing histiocytes can be found in giant cell
tumor specimens [19,20]. It was suggested to
differentiate the two diseases radiologically due to the
fact that most giant cell tumors are very much vascular-
ized. The presence of a sclerotic rim in BFH could also
be used to differentiate these two diseases [21].
One of the microscopic features is the presence of
lipid-bearing histiocytes - also called xanthoma cells -
sometimes dominating the histological picture in BFH.
As there are at least three reports of xanthomatous
lesions in the mandible [22-24], a comparison with BFH
seems reasonable. Xanthomas of the bone are tumor-
like accumulations of lipid-bearing histiocytes, either in
combination with hyperlipoproteinemia or as part of
other lesions like BFH. Xanthomas are no tumorous
proliferation of any cellular element of the bone [17].
Therefore it is not listed in the WHO histological classi-
fication of bone tumors [1]. Radiographically, xanthomas
lack a sclerotic rim. In contrast to BFH, extension into
the adjacent soft tissue is reported in xanthomas [25]. In
our case no extension in the surrounding soft tissue was
detected, although there was cortical disruption at the
lingual and buccal bulging.
The prognosis for BFH seems to be excellent with
almost no recurrence after complete surgical resection.
Due to the dominance of the bone mass close to the
dentoalveolar nerve, the piezoelectric unit was a usefull
tool to prevent nerve injury.
Ultrasonic waves are used in oral and maxillofacial
surgery for various diagnostic and therapeutic proce-
dures. They are applied in diagnostics, endodontics, the
removal of calculus from the teeth and, most recently,
osteotomies [26-29]. Depending on the indication, the
oscillation amplitude and frequency vary in accordance
with the power transmitted to the tissue. Special presets
are indicated for bone cutting procedures.
In the presented case the neurological scores from T1
to T4 demonstrate no dental nerve injury. No damage
to the nerve was detectable even though direct contact
of the working tip with the alveolar nerve was to be
assumed. This is in line with experimental in vitro stu-
dies where no damage even in direct contact to the
nerve was analyzed [10].
Follow-up examinations were obtained 3 and 6
months after surgery with no clinical and radiological
evidence of recurrence (Figure 10).
Conclusions
The purpose of the present article was to show the
advantages of the piezoelectric-assisted surgical removal
of a rare benign fibrous histiocytoma of the mandible
and give a precise description of the experience with
protecting dentoalveolar nerve.
BFH must be distinguished from non-ossifying
fibroma or giant cell tumors by clinical appearance as
well as histopathological appearance. As far as we know,
Figure 8 Intraoperative image showing the removal of the
bone with the piezosurgery device.
Figure 9 Intraoperative image after removal of the tumor.
Wagner et al. Head & Face Medicine 2011, 7:20
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Page 4 of 6
the prognosis of BFH seems to be excellent after com-
plete removal.
There is a therapeutical potential and benefit of the
Piezoelectric-assisted surgical saw in dentoalveolar sur-
gery. Piezosurgery® vibrates with a modulated ultrasonic
frequency. Because the vibration frequency of Piezosur-
gery is optimal for mineralized tissue it does not cut
soft tissue and therefore provides a technique for osteot-
omy to remove bony mass of the mandible and prevent
anatomic soft tissue injuries like dentoalveolar nerve
even in rare and complicated cases like this.
Consent statement
Written informed consent was obtained from the patient
for publication of this case report and accompanying
images. A copy of the written consent is available for
review by the Editor-in-Chief of this journal.
Funding
The article processing charges are funded by the
Deutsche Forschungsgemeinschaft (DFG), “Open Access
Publizieren”.
Author details
1Department of Cranio-Maxillo-Facial Surgery, Hannover Medical School,
Germany. 2Department of Pathology, Hannover Medical School, Germany.
Authors’ contributions
MW and MR contributed equally to this work. MW, MR, WT, HK, AME and
NCG conceived of the study and participated in its design and coordination.
MW and MR drafted the manuscript. AME and NCG were involved in
revising the manuscript. All authors read and approved the final manuscript.
Competing interests
The authors declare that they have no competing interests.
Received: 2 October 2011 Accepted: 31 October 2011
Published: 31 October 2011
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