At the 40th annual meeting of the Japanese Society of Oral Oncology, a workshop entitled “Can imaging accurately determine the resection margin？” discussed the discrepancies between imaging and histopathology in the evaluation of invasion depth of oral cancer.
A case of gingival carcinoma of the mandible, in which bone display CT images underestimated the bone marrow invasion, was presented. Retrospectively, it was speculated that ¹⁸F-FDG PET/CT might be significant in the evaluation of invasion depth of tumor tissue in bone marrow of the mandible. Additionally, texture analysis of PET/CT might be a promising method for deciding the treatment strategy in gingival carcinoma.
Although intraoral ultrasonography has been shown to be accurate in measuring the depth of invasion in T1/T2 tongue carcinoma, standardization of the examination method would be needed for dissemination of this beneficial technique.
Histopathologically, it is suggested that modern imaging techniques already have enough accuracy in the evaluation of invasion depth of oral cancer. Moreover, from the viewpoint of treatment outcomes, clinicians should note that histopathological information is also as important as the invasion depth.

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A retrospective investigation to explore the predictors of late cervical lymph node metastasis （LCLM） in stage Ⅰ-Ⅱ tongue squamous cell carcinoma （TSCC） was conducted. The subjects were 62 patients with stage Ⅰ-Ⅱ TSCC who underwent primary tumor resection as the initial treatment. The relationship of LCLM with the candidate factors of age （＜ 60 vs. ≥ 60 years）, gender （female vs. male）, 2017 UICC T classification （T1 vs. T2）, pathological differentiation （high vs. medium / low）, YK classification （1/2/3/4C vs. 4D）, perineural invasion, vascular invasion, pathological depth of invasion （pDOI ＜ 3.5mm vs. ≥ 3.5mm） and tumor budding （TB ＜ 4 vs. ≥ 4）. LCLM occurred in 15 cases （24.2％）, and the time of onset was within 2 years after primary surgery in all cases. Univariate analysis revealed significant differences in the 2017 UICC T classification, YK, pDOI, and TB. Furthermore, multivariate analysis indicated pDOI and TB as the independent predictors. LCLM was observed in 64.3％ of patients with pDOI ≥ 3.5mm and TB ≥ 4.
In conclusion, it is strongly suggested that patients with stage Ⅰ-Ⅱ TSCC （pDOI ≥ 3.5mm and TB ≥ 4） must be strictly followed for up to 2 years after primary tumor resection.

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In recent years, there has been strong demand for the provision of “precision cancer medicine” that provides optimal treatment for each individual. In Japan, a comprehensive cancer genome profiling test started in 2018. We present two cases and discuss the issues involved in applying this test for patients with malignant tumors in the oral region, along with a literature review.
A 79-year-old woman with right lower gingival cancer and a 73-year-old man with left lower gingival malignant melanoma underwent a next-generation sequencing-based multiplex gene assay （NCC Oncopanel test）. Both had already received standard treatment and were expecting to finish their standard cancer drug therapy at the time. The former patient was found to have TP53 （R282W） and CDKN2A （R58^＊） gene mutations; the latter patient presented no detectable genetic alterations. Their tumor mutation burdens were 1.6 and 6.2 Muts/Mb, respectively, and both were microsatellite stable. Neither was suspected of having hereditary neoplastic syndrome. According to the results of this test, consensus on a recommended treatment could not be established in the expert panel meeting.
In addition to tumor specific mutations, it is expected that the detection of tumor agnostic mutations and the selection of treatment options based on the results will improve in the future.

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Ameloblastoma is rare and the most aggressive and locally invasive odontogenic tumor derived from odontogenic epithelium with a tendency for recurrence and bone destruction. We report a case in which the initial symptom of nevoid basal cell carcinoma syndrome （NBCSS） was thought to be due to ameloblastoma. The patient was a 15-year-old male with no medical history or family history. The ameloblastoma of the mandible was removed; at 6 years after the operation, a dentigerous cyst developed in the left maxilla; at 9 years, an odontogenic keratocyst developed in the right maxilla; at 12 years, no recurrence was observed and the patient is being followed up. In NBCCS, which presents with various symptoms, the pathophysiology is not limited to major symptoms such as odontogenic keratocysts even in the maxillofacial region. It is important to deepen understanding of NBCCS diseases and make efforts for early diagnosis.

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Cholesterol embolism is a condition in which the atheroma in a large vessel wall collapses and cholesterol crystals leak into the bloodstream, causing periphery embolization, which may be caused by catheterization or cardiovascular surgery. In this paper, we describe a case of cholesterol embolism after superselective intra-arterial chemotherapy. The patient was an 81-year-old man with right oral-floor carcinoma （T2N1M0, stage Ⅲ）. Since the patient strongly desired to preserve organ function, he underwent a total of four superselective intra-arterial chemotherapy courses by the Seldinger method combined with radiotherapy （66Gy）. Before the fifth superselective intra-arterial chemotherapy course, right toe pain, purple-red spots, and sudden renal function decrease （serum Cr level; 1.92mg/dl, eGFR level; 26.9ml/min） were observed, and a histopathological diagnosis of cholesterol embolism was obtained from the tissue biopsy performed at the department of dermatology. Oral administration of steroids and prostacyclin preparations improved the right toe pain; however, renal function did not improve. After completing steroid therapy, the patient was followed up in the outpatient clinic. After 3 months, cervical lymph node resurgence was observed, and systemic drug therapy was initiated. After 10 months, the patient died of pneumonia. Reportedly, the Seldinger method causes cerebral infarction in approximately 1％ of cases. Conversely, cholesterol embolism, although extremely rare, is a disease with a poor prognosis and high probability of transitioning to hemodialysis. It is suggested that the disease should be fully considered when selecting treatment options.

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We describe a new plate replacement method using a resin frame to reposition the mandible in the position before reconstruction plate fracture.
The patient was an 89-year-old male who underwent segmental mandibulectomy, neck dissection, pectoralis major flap reconstruction, and plate reconstruction for left mandibular gingival carcinoma. Two years and eight months after the surgery, the reconstruction plate fractured. A full-scale three-dimensional model （3D model） was created to make a resin frame based on computed tomography taken before the fracture. Wire-holding grooves and screw holes were added to the resin frame to reduce the mandible in the position before the reconstruction plate fracture. After the fractured plate was exposed, the resin frame and fractured plate were ligated with a wire using wire-holding grooves. Subsequently, the resin frame was secured to the mandible with screws, and the position of the mandible was secured. After removing the fractured plate, a pre-bent reconstruction plate was secured in its place. With conventional methods, it is difficult to achieve an accurate position for the mandible during surgery; however, in the present case, the 3D model created based on previous CT data and the positional relationship replicated by the resin frame allowed favorable reproduction of the original mandibular position. The present method is useful for cases such as the present one, where the number of remaining teeth is limited and maxillomandibular fixation is not indicated.

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We experienced a case of carcinoma of the mandibular gingiva that extended deeply to the lower lip. Tumor excision while preserving the vermilion followed by forearm tendinocutaneous flap reconstruction was performed, which maintained good function and esthetics. The patient was an 84-year-old woman. The tumor was observed in the right mandibular gingiva （34mm×22mm） extending to the lower lip. A biopsy revealed a pathological diagnosis of squamous cell carcinoma. Resection was performed by bilateral neck dissection, with full-thickness resection of the lower lip while preserving the vermilion and marginal resection of the mandible. Defects in the oral cavity and lower lip were reconstructed by the forearm tendinocutaneous flap, and bridge tendon grafting was performed with the palmaris longus tendon for the resected orbicularis oris. The folded part of the forearm flap was de-epithelialized and sutured to the preserved vermilion. After the surgery, there was no insufficiency of the reconstructed lip, and the esthetic outcome was good. This method can maintain the sensation and muscle action of the lips by preserving the vermilion and should be considered in oral cancers extending to the lower lip if it is possible to preserve the vermilion.

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