case_images: PMC5933066_01
case_images: Intraoral appearance of the upper jaw. (a, b) Swollen nonulcerative mucosa in the buccal and palatal side gingiva (yellow arrow).
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case_images: fig1
case_images: Intraorally, the lesion involving the area from the upper left canine to the first premolar also showed evident buccal and palatal cortical expansion (Figures 1(a) and 1(b)).
case_images: Radiologic and computed tomography (CT) findings. (a) Panoramic radiograph showing a well-delineated radiolucent lesion (yellow arrows). (b, c) CT showing expansion and cortical bone osteolysis (yellow arrows).
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case_images: fig2
case_images: Panoramic radiography showed an extensive, relatively well-delineated radiolucent lesion extending from the left middle incisor to the second premolar with tooth displacement but no root absorption (Figure 2(a)). A computerized tomography (CT) scan also demonstrated expansion and absorptive destruction of both the buccal and palatal cortical plates (Figures 2(b) and 2(c)).
case_images: Microscopic features of the biopsy specimen. (a) Survey view of the biopsy specimen. (b) The cyst wall lined by a folded, thin, regular parakeratinized epithelium without rete ridges, and the basal layer lined by palisaded columnar cells with hyperchromatic nuclei (HE; original magnification: x12.5 (a) and x100 (b)).
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case_images: fig3
case_images: The histopathological appearance of a biopsy specimen was consistent with the odontogenic keratocyst (OKC) (Figures 3(a) and 3(b)).
case_images: Macroscopic and survey view of the surgically resected specimen. (a) Surgical specimen. (b) Invasive atypical squamous cell nests in the cyst walls (black arrow) (HE; original magnification: x1 (b)).
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case_images: fig4
case_images: Macroscopically, the surgical specimen was a cystic mass with a fibrous wall measuring 25 x 22 x 15 mm (Figure 4(a)). Microscopically, the lesion was cystic (Figure 4(b)) with a lining of parakeratinized stratified squamous epithelium.
case_images: Microscopic features of the surgical specimen. (a) Invasion of atypical epithelium (black arrow). (b) Invasive squamous epithelium irregularly migrating from the epithelial cyst lining similar to SCC. (c) High-power magnification. (d) Invasive nests, (e) p53, and (f) Ki-67 (HE and IHC; original magnification: x12.5 (a), x40 (b), x100 (c), and x200 (d), (e), and (f)).
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case_images: PMC5933066_01_CRIOT2018-7959230.005.jpg
case_images: fig5
case_images: Although the pathological findings were almost consistent with the OKC, focally invasive atypical squamous cell epithelia ware noted (Figure 5(a)). Epithelial dysplasia was evident in the areas around the invasive atypical squamous cell nests (Figures 5(b) and 5(c)). Immunohistochemistry showed that the invasive atypical squamous cell nests (Figure 5(d)) were positive for p53 (Figure 5(e)) and that the proliferative activity (MIB 1 index) was about 20% (Figures 5(f)).
case_images: Unusual ameloblastomatous change of the OKC. (a) Only part of the lining epithelium shows papillary hyperplasia with ameloblastomatous epithelial elongation. (b) The suprabasal layer shows stellate reticulum-like formation, and the basal layer shows palisading tall columnar cell nuclei with focally mitoses (arrowheads) (HE; original magnification: x40 (a) and x200 (b)).
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case_images: fig6
case_images: Unusual ameloblastomatous epithelial elongation with a stellate reticulum was observed in part of the lining epithelium (Figure 6(a)) and also in the epithelium with mitoses (Figure 6(b)).
case_images: Macroscopic appearance and microscopic features of the additional surgically resected specimen. (a) Resected specimen. (b) Cystic lesion in the palatal side of the second premolar. (c) Microscopically, locally invasive daughter follicles in many bone marrow spaces (arrows). (d) Invasive solid cystic follicles with a KAB-like growth pattern (arrows) (HE; original magnification x40 (c) and x200 (d)).
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case_images: fig7
case_images: This second surgical specimen measuring 35 x 30 x 25 mm included the left second premolar and maxillary sinus (Figure 7(a)). There was a cystic lesion, 8 x 7 mm in length, located in the palatal side of the second premolar (Figure 7(b)). Microscopically, this lesion appeared to be a typical OKC without malignant components, but there was marked local invasion to the bone marrow (Figure 7(c)). Solid variant OKC-like or keratoameloblastomatous microfollicles with keratin plugs were found in the bone marrow space (Figure 7(d)).