Keywords hybrid lesions - aneurysmal bone cysts - ossifying fibroma - central giant cell granuloma
Introduction
Hybrid lesions are incredibly uncommon compositions that have components of numerous
pathologies, each of which has a specific tumor category.[1 ]
[2 ] One or more recognized odontogenic cysts and/or tumors that have mixed histological
features and are present in the same primary location are referred to as hybrid odontogenic
lesions.[3 ] Dental practitioners have a problem with this category of lesions since their histogenesis
is debatable, their clinical behavior is still relatively unknown, and they exhibit
a variety of clinical-radiographic symptoms.[3 ] Less cases have been reported recently of hybrid lesions that combine an ossifying
fibroma (OF), an aneurysmal bone cyst (ABC), and a central giant cell lesion (CGCL).
According to the 2017 definition provided by the World Health Organization, CGCL is
a benign osteolytic proliferation that can occasionally be locally aggressive and
is made up of large, multinucleated osteoclast-type cells in a fibrous tissue stroma
that also contains hemosiderin and hemorrhagic deposits.[4 ] The name “aneurysmal bone cyst” is misleading because this lesion is not a cyst
and does not have an epithelial coating. It does have various-sized bloody spaces.[5 ] The ABC could start as a localized vascular disruption in bone.[6 ] ABC may be divided into three categories. The conventional or vascular kind (95%)
appears as a damaging lesion that grows quickly, expands, and invades soft tissue.
The solid kind (5%) may initially be seen as a radiolucency on a normal radiograph
or as little swelling.[7 ]
[8 ] The characteristics of both the vascular and solid varieties can be seen in a third
type or mixed variety. Because of reports of abrupt activation or fast expansion of
stable lesions, it might represent a transient phase of the lesion.[8 ] OF, also known as cement-ossifying-fibroma, is a benign bone tumor that affects
the facial skeleton. It is further divided into juvenile and conventional forms, each
of which has trabecular and psammomatoid subtypes.[9 ]
CGCL associated with fibrous lesions may be the result of a secondary reaction in
response to changes in the initial stroma of the lesion, where theoretically there
is an activation of the osteoclasts and their subsequent transformation into multinucleated
giant cells, all of this mediated by paracrine mechanisms. This is suggested as one
potential pathogenesis for hybrid lesions involving giant cells.[10 ] There is a need to publish such instances in the literature because there are so
few of them, making diagnosis and treatment more accurate.
Case Report
Having experienced painless swelling in her mouth, a 75-year-old woman visited a dental
hospital. The swelling was present in the lower anterior region of the lower jaw for
the last 18 months, which had grown gradually to its current size. The patient was
hepatitis B surface antigen (HBsAg) positive with a history of hypertension that was
present for 40 years and she was on medication for the same. The patient was not treated
before for the same. No history of trauma was present. Habit history and family history
were not significant.
Extraoral examination revealed a diffused swelling was present over the anterior region
of the lower jaw extending anterior-posteriorly from the corner of the mouth on the
left side to corner of the mouth on the right side, and superior-inferiorly from the
vermillion border of the lip to 3 cm lower to the inferior border of the mandible.
On inspection, the size was 5 × 8 cm approximately, the shape was roughly oval, the
margins were well defined, the color was pinkish red, the surface was tense and edematous,
and mentolabial fold was obliterated. On palpation, tenderness was absent, consistency
was firm to hard and temperature was raised ([Fig. 1 ]).
Fig. 1 Extraoral and intraoral photo on the first visit.
Intraoral examination revealed a diffuse swelling with labio-lingual expansion extending
anterior-posteriorly from the 36 regions to 47 regions posteriorly causing labial
vestibular obliteration and superior-inferiorly from the gingival margin into lingual
and gingival labial sulcus. The overlying mucosa had lobulated swelling that was ulcerated.
The size was 1.5 × 1 cm approximately, shape was roughly oval, borders were ill-defined,
the surface was ulcerated and edematous, reddish pink in color, and the margins were
well defined. On palpation, tenderness was absent, induration was absent, consistency
was soft to firm, and fixity to the internal structure was absent. Grade II mobility
was present with 31 32 41 42 ([Fig. 1 ]).
The provisional diagnosis was given as aggressive central giant cell granuloma. Differential
diagnosis was given as osteogenic sarcoma, ABC, and intermediate stage of fibro-osseous
lesion.
Orthopantomogram and lateral skull radiograph revealed that osteolytic lesion extending
from the symphysis region bilaterally involving the premolar and molar regions. Thinning
of the inferior cortex bilateral up to molar region with irregular margins was seen
with the remnant of internal septae seen in radiolucency ([Fig. 2 ]). Computed tomographic scan, which was taken after 14 days after the first visit,
revealed that there was a single large expansile, mixed lesion present in the body
of the mandible with radiopaque-radiolucent foci, showing multiple radiolucent loculi
with soap bubble appearance. The lesion showed corticated periphery ([Fig. 3 ]).
Fig. 2 Orthopantomogram and lateral skull radiograph.
Fig. 3 Computed tomographic scan showing coronal, axial, and sagittal sections.
Incisional biopsy revealed large multinucleated giant cell with 10 to 15 nuclei suggesting
giant cell granuloma ([Fig. 4 ]).
Fig. 4 Histopathology of incisional biopsy showing large multinucleated giant cell.
After the biopsy in 14 days, there was a rapid increase in intraoral swelling ([Fig. 5 ]).
Fig. 5 Rapid increase in the size of the lesion after 14 days of biopsy (preoperative photos).
The patient underwent an elective surgical procedure under general anesthesia and
nasotracheal intubation. As the patient was HBsAg positive, universal precaution was
taken.
Affected teeth were extracted along with the removal of a portion of the mandible
without disruption of the continuity of the mandible was planned. Segmental mandibulectomy
from the angle of the mandible of the right side to the 38 regions of the left side
of the mandible was done and reconstruction with pectoralis major myocutaneous flap
was done ([Fig. 6 ]).
Fig. 6 Segmental mandibulectomy with reconstruction with pectoralis major myocutaneous flap.
The resected specimen showed an exophytic grayish-black extensive lesion present over
the lower anterior jaw ([Fig. 7 ]). On the cut section, excessive bleeding was encountered resembling a blood-soaked
sponge with large cavernous spaces.
Fig. 7 Resected specimen.
When the resected specimen was sent for histopathology, hematoxylin and eosin stained
lesional tissue section in scanner view showed fibrocellular with large cavernous
or sinusoidal blood-filled spaces. In low power view, immature bony trabeculae lined
by osteoblastic rimming with numerous osteocytes are seen. Also, multinucleated giant
cells and young fibroblasts are seen in the connective-tissue stroma seen in low power
view. Under higher magnification, multinucleated giant cells with 10 to 15 nuclei
and immature plump fibroblasts are seen in the connective tissue stroma. Histopathological
diagnosis was given as an ABC with OF ([Fig. 8 ]).
Fig. 8 Histopathology of the resected specimen.
Discussion
The differential diagnosis for this lesion includes aggressive central giant cell
granuloma, ABC, intermediate-stage of fibro-osseous lesion, and osteogenic sarcoma.
It takes a combination of clinical, radiographic, and histological assessment to correctly
diagnose these disorders.
A benign yet locally destroying lesion that mostly affects the jaws is aggressive
central giant cell granuloma. Aggressive growth, cortical bone damage, and a high
recurrence rate are its defining features.[11 ] OFs and fibro-osseous lesions are two distinct medical conditions with unique histological
characteristics. A series of benign bone illnesses known as fibro-osseous lesions
are distinguished by the replacement of healthy bone with a fibroblastic stroma and
various degrees of mineralization.[12 ]
[13 ]
The process of ossification results in the development of mineralized bone and fibrous
tissue. Other bones, such as the long bones and craniofacial skeleton, can also develop
OFs. They appear as well-circumscribed, expansile lesions on radiographs that are
both radiolucent and radiopaque in appearance. OFs exhibit trabeculae of woven bone
together with fibrous tissue histologically.[14 ]
[15 ]
The most frequent primary malignant bone tumor, osteogenic sarcoma, primarily affects
children and young adults. The formation of osteoid, or young bone, distinguishes
it as it develops from primitive bone-forming cells. The metaphysis of long bones,
especially those at the knee, is a common site of involvement. Osteogenic sarcoma
presents radiographically as a destructive lesion that is aggressive and mixed in
lytic and sclerotic patterns. Histologically, it shows the production of osteoid and
pleomorphic malignant cells.[14 ]
[15 ]
A rare hemorrhagic bone condition called ABC only sometimes affects the jaws. The
lesion, which was caused by a localized vascular disruption, is widely accepted.[6 ] The “blow-out” effect or growth of the damaged bone that manifests in these sorts
of lesions is referred to as “aneurysmatic.”[16 ] The jaw's ABC lacks epithelial lining (pseudocyst).[11 ] It makes up 5% of all cranial and maxillofacial bone lesions and is most prevalent
where the marrow and vascular contents of the bone are both reasonably high. This
explains why ABC in the skull bones, which have less venous pressure, is uncommon.[17 ]
[18 ]
The concept of a hybrid lesion involving ABCs was first proposed by Kransdorf and
Sweet in 1992. They described cases in which the histological features of ABCs were
present along with additional features of other bone tumors, such as giant cell tumors,
osteoblastoma, or fibrous dysplasia. This hybrid nature of the lesion makes it challenging
to diagnose and treat accurately. The diagnosis of ABC hybrid lesions relies on a
combination of clinical, radiological, and histopathological findings. Radiographically,
these lesions may show a mixed pattern with characteristics of both ABC and the associated
lesion. Magnetic resonance imaging can provide further information on the extent of
the lesion and its relationship with adjacent structures.[19 ]
Thirty-two ABC plus lesions were found after a study of the literature; it was noted
that there is a preponderance of men and that the mandible is more likely to be afflicted.
The posterior area of the jaw is where more than 90% of ABC plus lesions are found.
Sixty-eight percent of the 32 ABC plus lesions had fibro-osseous lesions in common.
Giant cell lesions were linked to 32% of the lesions. From a lesion having no symptoms
to a painful, expanding, and destructive pattern, ABC exhibits a wide spectrum of
clinical characteristics.[20 ] The majority of the lesions, however, were asymptomatic swellings, which also existed
in our case. Female patient having a lesion in the mandibular anterior region is rare
that was present in our case.
In contrast to ABCs that develop in other long bones, ABC hybrid lesions usually exhibit
discomfort along with a propensity for rapid development, whereas ABCs that develop
in other regions of the body are frequently linked to malignant tumors including chondrosarcomas
and osteosarcomas.[18 ] ABCs have never encountered malignant or metastatic bone lesions. Additionally,
they are very infrequently linked to malignant ameloblastomas and aggressive neoplasms
like osteoblastoma.[21 ]
Jaw ABC's radiological appearance is somewhat unpredictable. The lesion may seem bony,
cystic with a honeycomb or soap bubble appearance, or eccentrically inflated. The
cortex may be perforated or destroyed, and a periosteal response may appear.[21 ] A mixed, radiopaque, or radiolucent lesion might exist. We found an expansile, mixed
lesion with radiopaque–radiolucent foci in the current instance. Additionally, the
lower anterior teeth appeared to be mobile. Since other lesions with a similar appearance
on radiographs, such as odontogenic cysts, ameloblastomas, central giant cell granulomas,
myxomas, or central hemangiomas of the bone, exist, it is impossible to diagnose the
lesion based solely on its radiographic appearance.[22 ]
According to histopathology, ABC is made up of many blood-filled sinusoidal gaps,
osteoid material, and multinucleated giant cells in a fibrocellular connective tissue
stroma. Variable quantities of hemosiderin pigments are also detected. This description
is diagnostic of ABC in its classic or vascular form.[16 ] In contrast, hemorrhagic foci with many fibroblastic and fibrohistiocytic components,
gigantic cells that resemble osteoclasts, osteoblastic differentiation zones with
osteoid, and calcifying fibromyxoid tissue are seen in the solid form. In the mixed
form, one can see both vascular and solid characteristics. The ABC + lesions have
a combination of vascular and solid form, as well as related lesions; they exhibit
multiple blood-filled holes in the fibrocellular stroma, as well as multinucleated
giant cells and the production of osteoid tissue.[23 ] The histological characteristics of the lesion in this instance matched those indicated
above, suggesting an ABC with an OF.
The total eradication of the lesion is often the goal of the ABC plus lesion treatment
strategy. The lesions might be divided by many bone septae and are often multilocular.
This makes surgical removal challenging. The methods of treatment are systemic calcitonin
therapy, curettage, block resection, diagnostic and therapeutic embolization, and
block removal. Several self-healing cases have been documented in some studies after
extensive follow-up. For the treatment of cases of aesthetic deformity, loss of continuity
of the mandible, and situations with a high risk of fractures, several writers have
advocated for prompt restoration of the defect using autogenous grafts.[20 ] In the present case, segmental mandibulectomy with reconstruction was done.
Conclusion
Only a very small number of cases of these associated hybrid lesions have been reported
in the literature. Due to their rarity and vague initial symptoms, these patients
confront doctors with diagnostic difficulty. Dentists have a critical role in the
diagnosis and treatment of hybrid lesions, and each lesion must be correctly classified.
Such cases should be reported in the literature so that a more accurate diagnosis
and course for treatment may be implemented.
