Ameloblastic Carcinoma - Secondary Type, A Rare Case Report and Distinction from Malignant Ameloblastoma-Juniper publishers
JUNIPER PUBLISHERS-OPEN ACCESS JOURNAL OF HEAD NECK & SPINE SURGERY
Abstract
Ameloblastic Carcinoma (AC) primarily is an
aggressive odontogenic tumour, which histologically consist of features
of both ameloblastoma and carcinoma. This requires more aggressive
surgical approach then its benign counterpart. Malignant Ameloblastoma
(MA) microscopically appears benign but shows metastasis. The authors
reported an extremely rare secondary type of Mandibular Ameloblastic
Carcinoma of a 50 year old Indian male with a complaint of swelling,
trismus, significant bone resorption with tooth mobility. This article
discussed about the clinical features, radiographic features,
management, and histological characteristics of AC and its distinction
from MA.
Introduction
Ameloblastic Carcinoma(AC) is a rare malignant
odontogenic tumour that has features of ameloblastoma intermingled with
features of carcinoma, regardless of whether it has metastasized [1] i.e. ameloblastoma in which there is histologically malignant transformation with less differentiated metastatic growth [2].
Malignant Ameloblastoma (MA) is the lesions that metastasizes and are
well differentiated benign lesions AC in both primary and metastatic
sites [3].
In contrast to ameloblastoma, presents more aggressive clinical
features, such as rapid growth, perforation of cortex, painful swelling
and trismus [4].
AC mostly occurs in posterior mandible region with only 1/3rd cases in
maxilla region, and mostly occurs in around 30 yrs of age [5-10].
Radiographic findings include a poorly defined radiolucency, sometimes
with focal radiopacities due to necrosis with dystrophic calcifications [7,8].
According to latest WHO 2005 update, (AC) are classified in to Primary
type i.e. histologic features of ameloblastoma with cytologic atypia and
Secondary type, i.e. malignant transformation of pre-existing benign
ameloblastoma [11].
Most cases of (AC) are denovo and less than 1% of ameloblastomas
undergo malignant transformation. Hence secondary type is less frequent
than primary [3,12-14].
In this article, a case of (AC) secondary type is presented and its
clinical examination, radiographic examination, histopathology and
management are discussed. Meanwhile the published articles about the
(AC) are reviewed and its distinction from MA is pointed.
Clinical Examination
A 50-year-old Indian male patient referred to our
department with the complaint of rapidly growing painless swelling of
the right side of lower jaw crossing midline with difficulty in chewing,
multiple mobile teeth over affected region. He had the past history of a
similar lesion over the right lower jaw, which was treated by
Hemimandibulectomy with Disarticulation of right TMJ 12 years back. The
histopathology then was suggestive of ameloblastoma. On extraoral
examination, a firm diffuse nontender swelling over right side of f(AC)e
extended superiorly from the right infraorbital region to the lower
border of mandible inferiorly. Medially, it extended up to one-third of
both upper and lower lips with an elevated angle of mouth and laterally 1
inch anterior to the angle of mandible with more mediolateral expansion
measuring about 10cm x 8cm x 6cm (Figure 1a).
Neither paresthesia was associated with the swelling nor was any
regional lymph node palpable. Intraoral examination revealed a painless
firm proliferative growth crossing midline up to the right anterior
border of ramus. The swelling was negative on aspiration (Figure 1b).
Radiographic Examination
3 Dimensional computed tomography showed hypodense
image of approximately 5cm x 7cm size present over left side mandibular
and submandibular region, an area of resorption over left mandibular
premolar region with att(AC)hed 2.4mm titanium reconstruction plate (Figure 2).
Incisional Biopsy
The patient was then planned for an incisional biopsy
under local anesthesia. Histopathological examination with H & E
stain was conclusive of diagnosis of AC.
Surgery
He was planned for resection of tumor under general
anesthesia. The submandibular incision was given and the tumor appeared
firm in consistency, surrounding the reconstruction plate. The tumor
appeared firm in consistency, surrounding the reconstruction plate. The
tumor was removed along with the reconstruction plate and reconstruction
was done with Pectoralis major myocutaneous flap (Figure 3a & 3b). Hemostasis (AC)hieved and closure done in layers. The postoperative recovery was uneventful.
Histopathology
Microscopic examination showed ameloblastlc islands
with palisading of peripheral cells showing reverse polarity. Within the
islands marked features of malignancy were seen that is increased
mitosis, hyperchromatism, and pleomorphism. Some of the islands lost its
arrangement of peripheral palisading columnar cells and exhibited
irregularly arranged squamous cells with mitotic figures, vesicular
nuclei and prominent nucleoli (appeared firm in consistency, surrounding
the reconstruction plate. The tumor was removed along with the
reconstruction plate and reconstruction was done with Pectoralis major
myocutaneous flap (Figure 4).
Followup
Then we referred the patient to department of
radiotherapy. They have given 25 fractions of 1.8Gy e(AC)h for a period
of 5 weeks (45Gy). Then they referred the patient to Department of
Pulmonary Medicine and Gastroenterology to evaluate distant metastasis,
reports was negative. The patient is on regular follow-up since 1 year
and doing well.
Discussion
In 1983, Shafers introduced the term (AC), which is a
rare malignant neoplasm that requires correct histologic diagnosis and
aggressive surgical intervention. The tumor cells resemble the cells
seen in ameloblastoma, but they show cytologic atypia. Mean time span
from symptoms to treatment is shorter for (AC) (11 months) as compared
with benign ameloblastoma (27 months) as its progression is faster [3,13].
Most (Ac), primary type, arise de novo and histologically defined as an
apparent malignant neoplasm that exhibits cytological malignancy,
including pleomorphism, hyperchromatic nuclei, and high mitotic rates.
The rare variety of (Ac), secondary type, is thought to occur from the
recurrent or pre-existing ameloblastoma, and it may have the histologic
features of a coexisting ameloblastoma [3,14,15].
The clinical features, biologic behaviour and treatment of (AC),
secondary and primary types, are almost identical. Because of its
rarity, no full proof therapeutic guidelines exist for (Ac). Some
clinicians recommend wide resection. However a small number of reports
have described radiation therapy and chemotherapy as treatment modality
with Ion beam therapy as a new measure.
After reviewing all article on AC present in Pubmed
and Cochraine online digital library till date we got that AC mostly
occurs in sixth to seventh decade of life. They are seen twice as often
in male patients as in female patients. The most commonly involved area
is the posterior portion of the mandible [7]. Involvement of the maxilla by (AC) seems to be less frequent [3,7,16,17].
The most common sign described has been swelling, although others
include associated pain, rapid growth, trismus and dysphonia [7].
The radiographic appearance of the lesion was consistent with that of
an ameloblastoma except for the presence of some focal radiopacities,
apparently reflecting dystrophic calcifications [7].
MA is a very rare tumor, defined in 1992 by the World
Health Organization (WHO) as "a neoplasm in which the pattern of an
ameloblastoma and cytologic features of malignancy are shown by the
primary jaw lesion and/or by any metastatic growth. "The term MA was
especially controversial because of the former WHO classification, in
which the diagnosis was based on the presence of metastasis.
Histologically, MA does not show uniform proliferation, but it has
cellular pleomorphism. Spindling of the cells is recognized in some
solid proliferating areas [18].'
The two forms of malignancy described in association
with ameloblastomas are the MA and (AC). For a diagnosis of MA, the
cardinal feature is metastatic spread, because the histological
appearance of the primary and metastatic lesion(s) is indistinguishable
from the typical benign ameloblastoma. The most common sites of
metastases are reported to be the chest (lungs, pleura, hilar nodes) in
75% of cases and the cervical lymph nodes or spine in 15% [19].
The mode of spread of MA is debated as being either by inhalation at
the time of surgery, haematogenous or lymphatic spread. The management
of MA [20,21].
Isolated and discrete lung metastases have been treated by open
thor(AC)otomy and wedge resection 6V15 and chemotherapy has occasionally
been used successfully [22-24].
In the present case the lesion is confined clinically
and radiographically, within the mandible with evidence of extension of
a carcinoma into gingiva, alveolar ridge, floor of mouth, but no
evidence of metastasis to distant site. Microscopically, there is
carcinoma as well as morphologic features that resembled ameloblastoma,
arose in a preexisting ameloblastoma. These clinical, radiographic,
pathologic findings support the diagnosis of an (AC) secondary type.
Only a limited number of (AC)s secondary type cases have been reported
in the English-language literature till 2017, so this present report adds one more case to the scanty number of publication.
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