2023 Volume 65 Issue 4 Pages 281-283
Abstract: Sclerosing odontogenic carcinoma (SOC) is a very rare malignant odontogenic tumor characterized by sclerotic stroma and single-file cord-like tumor cell structures. A 38-year-old man presented with extraoral swelling and right mental region paralysis. Panoramic radiography revealed an ill-defined radiolucent lesion extending from the right mandibular ramus to the right lower canine. Magnetic resonance imaging showed tumor invasion into the right inferior alveolar nerve and masseter muscle. Hemimandibulectomy, bilateral neck dissection, and mandibular reconstruction were performed using a rectus abdominis musculocutaneous flap and a titanium plate. Histopathology and immunohistochemistry confirmed SOC diagnosis. No recurrence occurred in the 1-year follow-up. In this paper, a case of SOC with a high Ki-67 labeling index was reported. Since SOC is prone to nerve invasion, treatment is resection with an appropriate surgical margin.
Sclerosing odontogenic carcinoma (SOC) is an intraosseous malignant tumor characterized by high local invasion, first reported by Koutlas et al. [1] in 2008. The histopathological features of SOC include small cord-like foci with dense, sclerotic stroma and epithelial cells arranged in a monolayer according to the 5th edition of the World Health Organization classification of Head and Neck tumors. However, there have been limited reports on SOC to date, and the pathogenesis of this tumor remains unclear. Furthermore, SOC shares histologic features with tumors such as poorly differentiated primary intraosseous carcinoma and clear cell odontogenic carcinoma, complicating initial diagnosis based on biopsy specimens. Some cases have reported nerve invasion, highlighting the importance of early diagnosis and appropriate treatment choice for SOC management. This report on SOC with a high Ki-67 labeling index adds to the existing knowledge of this extremely rare malignant odontogenic tumor.
A 38-year-old man experienced paralysis of the right mandible. Due to a lack of improvement, he visited a general hospital. An incisional biopsy suggested a malignant odontogenic tumor, but a definitive diagnosis was not reached. He was referred to authors’ institution for further examination and treatment. Extraoral swelling of the right mandible and paralysis of the inferior alveolar nerve were noted. Intraorally, swelling was observed on the buccal side of the right mandibular molar, but no tooth movement was detected. Panoramic radiographs revealed extensive and diffuse bone resorption from the mandibular ramus to the lower canine without obvious tooth root resorption (Fig. 1A). Computed tomography (CT) demonstrated buccal cortical bone destruction and tumor invasion into the masseter muscle. An ill-defined radiolucent lesion with mandibular bone destruction extending to the mandibular edge was observed (Fig. 1B, C). T2-weighted magnetic resonance imaging (MRI) indicated invasion of the solid tumor into the right inferior alveolar nerve and masseter muscle (Fig. 1D). Positron emission tomography-CT (PET-CT) showed fludeoxyglucose accumulation (maximum standard unit value, 12.0) in the right mandible (Fig. 1E). No evident cervical metastatic lymph nodes or distant metastases were detected. A biopsy performed at the previous hospital was re-evaluated by oral pathologists, suspecting SOC, but a definitive diagnosis was not reached. The patient underwent hemimandibulectomy and bilateral neck dissection (right; supraomohyoid neck dissection, left; submandibular dissection), followed by mandibular reconstruction using a rectus abdominis musculocutaneous flap and a titanium plate. An intraoperative frozen section diagnosis confirmed the absence of tumor cells in the inferior alveolar nerve, with no residual tumor cells. The patient was followed-up for approximately one year without evidence of disease recurrence.
The surgical specimen was a solid mass (90 × 40 × 18 mm) occupying the mandible, with intact oral mucosa (Fig. 2A). Histopathological examination revealed cords, small nests, and single-file proliferation of tumor cells with abundant fibrous stroma (Fig. 2B, C). Tumor cells exhibited eosinophilic cytoplasm and round to irregularly shaped nuclei. The stroma consisted mainly of sclerotic collagen fibers. Mitotic index was 9 per 10 high power fields in the areas of high tumor cells density. The obvious abnormal mitosis was not observed. The tumor was primarily proliferative within the mandible and partially infiltrative into extraosseous tissue, causing cortical bone destruction. Perineural invasion was observed. Immunohistochemically, tumor cells were positive for AE1/AE3, cytokeratin (CK) 5/6, CK14, CK19, and p63 (Fig. 2D-E). The Ki-67 labeling index was approximately 30%, indicating relatively high proliferative activity (Fig. 2F). Based on these histopathological findings, the tumor was diagnosed as SOC. No cervical metastatic lymph nodes were identified.
Preoperative findings of the tumor. (A) Panoramic radiograph showing ill-defined radiolucent lesion of the right mandible. (B) Axial CT image indicating buccal cortical bone destruction. (C) The tumor invaded the inferior border of the mandible as indicated by the sagittal CT image. (D) T2 weighted MRI suggesting that the ill-defined region extended to the buccal side and indicating tumor invasion of the masseter muscle. (E) PET-CT showed that fludeoxyglucose accumulated mainly in the right mandibular molar lesion (maximum standard unit value, 12.0).
Photographs of surgical specimen and Hematoxylin-Eosin (HE) and immunohistochemical staining. (A) Surgical specimen of the tumor. The masseter muscle and medial pterygoid muscle, which were suspected to be invaded by the tumor, were resected. (B) HE staining image. (C) High power view of the HE staining image. Tumor cells exhibit a single-file like array pattern. (D-F) Immunostaining for CK5/6 (D), CK19 (E) and Ki-67 (F). Ki-67 labeling index was approximately 30%.
SOC is an extremely rare odontogenic malignancy and the number of cases is still very small [1,2,3,4,5,6,7,8,9,10]. Although there are no clinical features suggestive to SOC, many cases present with painless swelling and, in some mandibular cases, inferior alveolar nerve paralysis [1,2,7]. Radiographical findings for SOC are highly variable, but many cases exhibit unilocular or multilocular radiolucency with jaw bone swelling, and tooth roots adjacent to the tumor may be absorbed. One case presented irregular and extensive lytic changes with ill-defined borders, patchy calcification, and periosteal formation in the labial and buccal cortex, resembling osteomyelitis [7]. That case was initially suspected to be “Garrè’s osteomyelitis.” Due to the variability of radiographical features, malignant tumors might not be initially suspected. Biopsy combined with other imaging studies (MRI, PET-CT) is preferred for diagnosis.
Surgical resection, including extended resection, is the first-line treatment for SOC. As previously reported, three cases of recurrence have been reported [2,6,10], one treated with extended resection and chemotherapy after recurrence [2], and the other with radiotherapy [6]. A surgical margin of at least 5 mm is recommended for this tumor based on previous reports [8]. A case of cervical lymph node metastases has been reported, so it is important to consider performing neck dissection, especially in advanced cases [10]. Chemotherapy or radiotherapy has been administered in some cases, but evaluating their effect on SOC is challenging due to the lack of detailed descriptions in previous reports [1,2,3,6,10].
In this case, the main clinical features included jaw bone swelling due to increased tumor size and paralysis in the area innervated by the inferior alveolar nerve, with little or no pain perception. CT revealed an ill-defined radiolucent lesion with bone destruction, but no obvious tooth root resorption. The CT images suggested the possibility of a malignant tumor, prompting immediate additional imaging studies and biopsy. For SOC treatment, hemimandibulectomy and neck dissection were performed in this case. Due to their high nerve invasion potential, it is crucial to confirm the absence of residual tumor at the nerve end, especially in mandible cases. In this case, intraoperative frozen section diagnosis was performed to verify the absence of tumor cells in the proximal side of the inferior alveolar nerve.
Hematoxylin-Eosin staining revealed that tumor cells exhibited a single-file growth pattern with little nuclear atypia and abundant fibrous stroma. Immunohistological studies showed that the tumor cells were positive for AE1/AE3, CK5/6, CK14, CK19, and p63, which are generally consistent with the immunohistological features of SOC. However, the Ki-67 labeling index was about 30%, which is slightly higher than in previous reports. Many reports have found a Ki-67 labeling index of less than 10% in SOC [2,4,5,6,7,9]. Since SOC is an extremely rare malignant odontogenic tumor, understanding all its pathological features remains challenging. Malignant tumors may not be initially suspected, so careful attention should be paid when diagnosing SOCs. Currently, the efficacy of chemotherapy or radiotherapy for SOC has not been established, suggesting that surgery should be performed at an early stage.
The authors have no conflicts of interest to disclose.
Data will be made available on request.
None
Informed consent was obtained from the patient for publication.
The authors thank Editage (www.editage.com) for English language editing.
