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We report a case of a fibrous odontogenic lesion occurring in the maxilla of a man in his 60s. The patient presented with an asymptomatic radiolucent area related to the upper left premolar on radiography. Histological examination of the lesion obtained through an incisional biopsy revealed dense fibrous connective tissue containing small, rounded islands of odontogenic epithelium. The differential diagnoses included central odontogenic fibroma and sclerosing odontogenic carcinoma. Despite being completely different entities, the histological similarities between the two tumors raise diagnostic challenges, with fibrous connective tissue and odontogenic epithelium being the common features. Owing to the finding of unclear small or thin epithelial nests with a high nuclear-cytoplasmic ratio and despite its small size, the lesion was suspected of being malignant, and a maxillary resection was performed. Sections from the resected specimen displayed a small or tiny odontogenic epithelium with cellular atypia and invasion by epithelial cells in and around the nerve fasciculi; therefore, a final diagnosis of sclerosing odontogenic carcinoma was made. Nonetheless, the presence of an odontogenic epithelium in or around the nerve fascicles is not always an evidence of malignancy in the jaw. Caution should be exercised when differentiating invasive epithelia from epithelial residues to provide appropriate treatment. [ABSTRACT FROM AUTHOR]

Purpose: This observational study aimed to elucidate the pathophysiology of subchondral cysts (SC) in the temporomandibular joint (TMJ) and examine the results of conservative therapy administered to patients with SCs in the TMJ., Methods: The study included 41 patients with SCs, extracted from 684 consecutive patients who underwent magnetic resonance imaging (MRI). The anatomical features of SCs and positional abnormalities of the articular disc were initially evaluated using MRI. A second MRI examination was performed for 28/41 patients at 40-107 months (mean, 66 months) after the first MRI. The joint space, anteroposterior width of the condylar head (WiC), articular eminence angle (AEA), and visual analog scale of jaw pain (VAS) were assessed alongside the MRI examinations., Results: Most SCs were present in the anterosuperior and central condyle. Disc displacement was observed in 100% of 42 TMJs with SCs. Of the 29 joints in 28 patients, SCs in 19 joints resolved with time, whereas SCs in 10 joints persisted. A significant increase in the WiC and a significant decrease in AEA and VAS scores were observed on the second MRI scan., Conclusions: SCs tended to form in the anterosuperior and central parts of the condyle, where mechanical loading was likely to be applied. SCs are strongly associated with articular disc displacement. Two-thirds of SCs resolved over time, accompanied by resorption and osteophytic deformation of the condyle. SC might not be an indicator for the start of surgical treatment, and nonsurgical treatment could improve the clinical symptoms of patients with SCs.