Page 34 - AAOMP Meeting 2019

POSTER ABSTRACTS - TUESDAY, JUNE 11, 2019

#19 GHOST CELL ODONTOGENIC CARCINOMA ARISING IN A PREVIOUS CALCIFYING
ODONTOGENIC CYST – A CASE REPORT AND REVIEW OF LITERATURE
Dr. Ioana Ghita (University of Maryland Baltimore), Dr. Michael Nagai (University of Maryland
Baltimore), Prof. Kristen Stashek (University of Maryland Baltimore), Prof. John Papadimitriou
(University of Maryland Baltimore), Prof. Joshua Lubek (University of Maryland Baltimore), Prof.
Donita Dyalram (University of Maryland Baltimore), Prof. Rania Younis (University of Maryland
Baltimore)
Introduction:Ghost Cell Odontogenic Carcinoma(GCOC) is a rare malignancy of odontogenic origin. It
is characterized by ghost cell aberrant keratinization, dentinoid deposition in variable quantities, and evidence
of malignant cellular features. It has unpredictable prognosis due to the wide variety of growth patterns and
the limited number of reported cases.
Materials and methods: The clinical, histological and immunohistochemical (IHC) features of a rare case
of GCOC are presented, in addition to a summary of literature review.
Results: A 36y/o AA male presented with a long-standing history of right sided facial swelling, difficulty with
speech and right sided nasal obstruction. Clinical examination revealed a large mass encompassing the right
maxilla with significant palatal expansion and ulcerated overlying palatal mucosa. An incisional biopsy of the
lesion was performed which showed a Calcifying Odontogenic Cyst (COC). The patient underwent right
subtotal maxillectomy and reconstruction of maxillary defect with fibula-osteocutaneous free flap. The
excisional biopsy revealed odontogenic epithelium proliferating in the form of broad sheets and strands with
columnar ameloblast-like peripheral cells, central large cells with vesicular nuclei, areas of ghost cell
keratinization, in addition to malignant cellular features of abnormal mitotic figures, hyperchromatism,
pleomorphism and areas of comedonecrosis. Margins showed invasion into the maxillary alveolar bone and
nasal septum. A small area of classic COC was noted on one of the examined sections. The IHC profile
showed lesional cells to be strongly positive for beta-Catenin, Ki-67 (proliferative index of ~75%) and focal
areas of diffuse nuclear staining of p53. A diagnosis of GCOC arising in a previous COC was determined based
on H&E and IHC review.
Conclusion: It is important to recognize this entity to avoid possible underdiagnoses since this is an extremely
rare tumor that may arise in otherwise innocuous COC. This case represents less than 50 reported cases in
literature.

#20 ATYPICAL PERIPHERAL AMELOBLASTOMA WITH LIKELY MALIGNANT
TRANSFORMATION
Ms. Y.W. Stacy Cho (Harvard School of Dental Medicine), Dr. Sook-Bin Woo (Department of Oral
Medicine, Infection and Immunity, Harvard School of Dental Medicine), Dr. Reshma Menon
(Harvard)
Peripheral amelobastoma (PA) is a rare odontogenic tumor, arising from either the basal cell layer of surface
epithelium or dental lamina rests. PA presents as an exophytic growth in the soft tissues overlying tooth-
bearing areas, with a predilection for the mandibular premolar region (32.6%). PA, unlike intraosseous
ameloblastoma, exhibits innocuous biological behavior and requires only conservative surgical excision.
This is a case of PA that presented in lingual gingiva of teeth #27 and 28 in a 17-year-old female with marked
cytologic atypia. A periapical radiograph of the quadrant was unremarkable. Histologic examination
revealed a basaloid neoplasm adjoined with surface epithelium. The tumor islands had two distinct cell
populations. In one, the islands consisted of basaloid cells with overlapping nuclei that were pleomorphic
and hyperchromatic, with many mitotic figures. The peripheral cells exhibited slight reverse nuclear
polarization while other areas had squamoid differentiation. The second population of cells was organized
as interlacing narrow cords with small, round, regular nuclei with dispersed chromatin, minimal nuclear
crowding and no mitotic activity. These cells were also in continuity with the surface epithelium and
transitioned into the first population of atypical cells. The immunohistochemical study for CK 19 was
strongly positive within all tumor cells while the studies for Ber-EP4, BCL-2 and smooth muscle actin
were negative. The Ki-67 index varied from <1% in the benign-appearing superficial cords of tumor cells
to >80% in the hypercellular areas with cytologic atypia. The final diagnosis was that of an atypical PA with
marked cytological atypia, suspicious for malignant transformation. Currently, there are three cases of
th th
malignant transformation of PA, all of which occurred in males in the 4 -8 decades and in the maxillary
canine-premolar region. Two of the three cases showed no recurrence after a year following excision,
similar to our patient.