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ISSN : 1225-1577(Print)
ISSN : 2384-0900(Online)
The Korean Journal of Oral and Maxillofacial Pathology Vol.44 No.1 pp.29-35

Odontogenic Carcinoma Arising from Odontogenic Keratocyst

Kihyun Im1), Dawool Han2), Junghun Kim1), Woong Nam1)*
1)Department of Oral and Maxillofacial Surgery, Dental Hospital, Yonsei University, Seoul, Korea
2)Department of Oral Pathology, Dental Hospital, Yonsei University, Seoul, Korea
Correspondence: Woong Nam. Department of Oral Surgery, Oral Cancer Research Institute, Yonsei University College of Dentistry, Seoul, Korea, 50-1 Yonsei-ro, Seodaemoon-Gu, Seoul, 03722, Korea. Tel: +82-02-2228-2971 E-mail:
January 31, 2020 February 7, 2020 February 7, 2020


Odontogenic keratocyst (OKC) is aggressive compared to other odontogenic cysts, but its malignant transformation is extremely rare. Odontogenic carcinoma may arise from an odontogenic cyst such as OKC. Here in, we introduce a case of odontogenic carcinoma assumed to have arisen from a preexisting OKC. Abnormal clinical and radiologic features seen in a previous or existing cyst may be warning signs of malignant transformation.

치성각화낭에서 발생한 치성 암종

임 기현1), 한 다울2), 김 정헌1), 남 웅1)*
1)연세대학교 치과대학병원 구강악안면외과



    Odontogenic keratocyst(OKC) comprises about 10-20% of gnathic cysts1). They occur most commonly in the mandible, especially in the posterior body and ramus2). In the past, OKC was renamed as keratocystic odontogenic tumor(KCOT) because it was regarded to have characteristics more consistent of a benign neoplasm rather than those of a cyst3). However, according to the World Health Organization(WHO) classification of odontogenic lesions updated in 2017, evidence for classifying OKC as neoplasm was considered to be insufficient and was re-classified as a cyst, regaining its name as OKC1,4).

    OKC shows more aggressive behavior compared to other odontogenic cysts and are known to have a higher recurrence rate depending on the type of surgical procedure5). Despite its locally destructive behavior and high recurrence rate, malignant transformation within the cystic epithelium lining of OKC is extremely rare. Carcinoma occurred from OKC was first reported by Areen et al. in 19816) and other reports have followed since7-10).

    In this study, we report a case of a 50-year-old male patient who had undergone hemi-mandibulectomy and fibula free flap due to odontogenic carcinoma progressed from a known OKC.


    The 50-year-old male patient was referred to the local clinic because of swelling and pain in the lower right jaw. The patient had no past medical history except hypertension.

    In the panoramic view taken at the first visit, scalloped appearance of radiolucent lesion with clear margin was observed in the right mandibular body and ramus area (Fig. 1). Also, impacted #48 tooth was in contact with the lesion. In the computed tomography (CT) images, an approximately 4.4cm expansile cystic lesion with cortical bone destruction at medial cortex of mandible, adjacent soft tissue swelling, fluid infiltration and facial thickening were observed (Fig. 2).

    Cyst enucleation and extraction of #48 were performed under general anesthesia. The cyst lesion was sent for pathologic examination. On pathologic examination, a flat parakeratinized stratified squamous cystic epithelium was observed (Fig. 3A). The basal cells were palisaded. The pathologic diagnosis was OKC.

    After surgery, the patient was checked at 1 week, 3 weeks, 1 month, and 2 months postoperatively. There were no signs of recurrence or pathologic interval changes at that period (Fig. 4A-B). At 3 months after enucleation, there were no specific symptoms complained by the patient. However, slightly increased radiolucency was observed on panoramic view in the mid-superior area of the previous surgical region (Fig. 4C).

    6 months after surgery, the patient complained of swollen gingiva and severe pain on the post-surgical site. The right lower buccal and lingual gingiva observed swelling and pus discharge with surface ulceration. Increased bone destruction was observed around #47 in the panoramic view (Fig. 5). The #46, 47 teeth were extracted due to severe mobility, and an incisional biopsy was performed with the jaw lesion. Magnetic resonance imaging (MRI, Fig. 6) and Positron Emission Tomography – Computed Tomography (PET-CT) findings were consistent with a malignant tumor. Under general anesthesia, wide excision, hemi-mandibulectomy, supraomohyoid neck dissection, reconstruction of soft and hard tissue defect with fibula free flap was performed.

    Pathologic examination of the lesion was observed as followed. Mixed areas of cystic epithelium and solid tumorous growth was seen. The cystic portion (Fig. 3B) has a similar architecture to OKC, in addition revealed severe cellular atypia and occasional bulbous downward growth. The solid portion was composed of tumor islands with either ameloblastic-like polarity and clear cell changes (Fig. 3C) or general squamous cell carcinoma appearances (Fig. 3D). The tumor cells were hyperchromatic and pleomorphic. After wide excision, the overall tumor cells were observed to be highly infiltrative within the jaw bone. An association with overlying oral mucosa was not confirmed and the lesion was assumed to be a primary intraosseous lesion. The final pathologic diagnosis was odontogenic carcinoma.

    After surgery, the patient has undergone periodic follow-ups for a year and no signs of recurrence has been noticed.


    Odontogenic carcinoma is classified into five detailed types; ameloblastic carcinoma, sclerosing odontogenic carcinoma, clear cell odontogenic carcinoma, ghost cell odontogenic carcinoma, and primary intraosseous carcinoma. Our case had mixed histological features of ameloblastic carcinoma, clear cell odontogenic carcinoma and squamous cell carcinoma, which made it difficult to define it as a specific type of odontogenic carcinoma. The tumor has a cystic epitheliumlike region as well, which is not general in odontogenic carcinoma.

    Odontogenic carcinoma can arise from odontogenic cysts, odontogenic tumors or de novo. Residual apical radicular cyst and dentigerous cyst are the most common odontogenic cyst known to have malignant transformation11). The presence of a cyst and contiguous carcinoma has been explained though three possible theories12): 1) individual synchronous cyst and carcinoma arosal; 2) cystic transformation of a preexisting carcinoma or 3) carcinoma arising from a preexisting cyst. This case of odontogenic carcinoma was suspected to have originated from its preceded OKC because of a few number of evidences observed in the pathological specimen. Full enucleation of the primary lesion revealed a benign cyst with no evidence of malignancy which was consistent with the benign characteristics on radiologic images. Although most of the malignant tumor, the recurred lesion, was composed of solid tumor islands, there were portions of cystic architecture that exhibited parakeratin, yet severe cellular atypia as well. Moreover, the overlying oral mucosa or gingiva sulcus epithelium, which are candidates for carcinoma development, did not display any evidence of malignancy, suggesting a primary intraosseous lesion.

    Radiologic changes in post-operative regions such as increased radiolucency and irregular marginal features raise a warning signal for not only recurrence or post-infection, but malignant transformation of remnant epithelium. Although the occurrence of malignant transformation in odontogenic cyst is rare, abnormal clinical and radiologic characteristics in post-enucleated cysts or cysts confirmed by incision and still before excision should be evaluated for possible tumorous change. Multiple biopsy, specifically made at the irregular site, may benefit accurate diagnosis. The prognosis of odontogenic cysts are more superior than carcinoma, yet periodic checkups are needed to confirm complete healing.



    Panoramic view taken at the first visit. Scalloped appearance of radiolucent lesion with a clear margin was observed in the right mandibular body and ramus area. An impacted #48 tooth was in contact with the lesion.


    Computed tomography (CT, contrast) taken at the first visit (A: coronal bone window, B: coronal soft tissue window, C: axial bone window, and D: axial soft tissue window). An approximately 4.4cm expansile cystic lesion with endosteal scalloping at the right ramus and body of mandible was seen. Cortical breach at the medial cortex of mandible is noticed. An adjacent soft tissue swelling, fluid infiltration, and facial thickening were observed.


    Histopathologic examination (Hematoxylin and eosin stain, A: Primary specimen, B-D: Recurred specimen, 7 months after enucleation)

    The cyst was lined by flat parakeratinized epithelium which had palisaded basal cells (Lu : Lumen, CE : Cyst epithelium, Original magnification x200)Focal cystic features seen in the recurred specimen. The epithelium featured dysplastic characteristics, such as loss of polarity, pleomorphism and hyperchromatism. (Original magnification x200)The recurred specimen was mainly composed of infiltrating malignant epithelial islands. Areas with central clear cell change (inset) and ameloblastic differentiation, including peripheral reversed polarity, was noticed. (Original magnification x200, inset x400)Other areas revealed squamous cell carcinoma-like cellular features (Original magnification x200).Reactive bone formation within the infiltrative tumor (T: tumor, Original magnification x100).Normal, non-tumorous oral mucosa overlying the tumor (Arrows: normal oral mucosa, B: normal cortical bone, R: reactive bone and tumor, Original magnification x12.5).


    Panoramic view taken at after surgery (Post-operative month; A: 1 month, B: 2 months and C: 3 months).

    A: Bone healing state was observed on the lesion.B: No specific interval change since Fig. 4A.C: Slightly increased radiolucency (arrow) was observed near the apical and posterior side of #47.


    Panoramic view and cone beam computed tomography (CBCT) taken at 6 months after surgery (A: panoramic view, B: coronal view and C: axial view). Increased bone destruction and soft tissue shadow at the surgical site were suspected of malignant transform or post-operative infection.


    Magnetic resonance imaging (MRI) image of the recurrent lesion (Contrast, A: coronal T1, B: coronal T2, C: axial T1, D: axial T2). Malignant expansile soft tissue tumor arising from right lower alveolar ridge, approximately 3.8-cm. Right retromandibular trigone extension and mandible destruction by the tumor is seen. Multiple lymph node metastasis in right level I-II, less than 2cm are seen.



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