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A solitary myofibroma (MF) is an unusual spindle cell neoplasm that usually arises in the soft tissue, skin, or bone of the head and neck region in infancy. We report an extremely rare case of MF of the mandible in an 18-year-old Japanese woman together with the conventional histologic, immunohistochemical, and electron microscopic findings. The tumor was well circumscribed and composed of fibroblast-like or myofibroblast-like spindle cells. On immunohistochemical evaluation the tumor cells were positive for vimentin, α-smooth muscle actin, HHF-35, and calponin, but negative for neurogenic antigens and markers for vascular endothelial cells. The Ki-67 labeling index was 10 % and the p53 labeling index was 10 %. Ultrastructural examination revealed smooth muscle cell differentiation. The patient was treated by surgical resection and underwent follow-up without any signs of recurrence. MF presents a wide range of differential diagnosis, including benign and malignant neoplasms. Therefore, accurate diagnosis may avoid an unnecessarily aggressive therapy. [ABSTRACT FROM AUTHOR]

Solitary fibrous tumor (SFT) is a rare mass-forming soft tissue tumor that occurs most commonly in the pleura, but has been described in various extrathoracic sites. Extrapleural manifestation of SFT, particularly in the head and neck region, is rare. The most common extrapleural site is the oral cavity; these tumors have also been described in the orbit, nasopharynx, paranasal sinuses, salivary glands, and larynx. We report an extremely rare case of a SFT in the subcutaneous region of the cheek. This tumor in the left cheek was a large firm mass, approximately 8.5 cm × 6 cm in size and was successfully treated by surgical resection. Immunohistochemistry revealed reactivity for vimentin, CD34, and bcl-2, but no staining for cytokeratin, epithelial membrane antigen, S-100, desmin, caldesmon, actin, α-smooth muscle actin, CD117, and CD99. Immunohistochemical study is the key to establish a definitive diagnosis of SFT, and ultrastructural study is also useful for making an accurate diagnosis. The patient recovered uneventfully without evidence of tumor recurrence 2 years after surgery. [ABSTRACT FROM AUTHOR]

In the pathological diagnosis of oral squamous cell carcinoma, we often confront the difficulty of determining whether it is invasive carcinoma or epithelial dysplasia. Recently, myelin and lymphocyte protein (MAL; T-cell differentiation-related gene) has been reported to be a candidate gene suppressed in esophageal carcinoma. When we performed cDNA microarray analysis, we found that gene expression of MAL was significantly downregulated in oral squamous cell carcinoma (OSCC). We evaluated the expression of the MAL gene by laser microdissection and real-time PCR methods and protein localization by immunohistochemistry. The gene expression of MAL was significantly decreased in OSCC compared with normal epithelium ( P < 0.05). Furthermore, protein expression of MAL disappeared gradually in proportion to malignancy. The results suggest that MAL plays an important role during oral carcinogenesis and that the gene may have potential as a biomarker target for OSCC. [ABSTRACT FROM AUTHOR]

Inflammatory myofibroblastic tumor (IMT) of the oral cavity is an extremely rare clinical and pathological disease entity. It was originally described in the lung but has recently been reported in various anatomic sites. We report such a case of inflammatory myofibroblastic tumor of the mandible in a 14-year-old girl. The patient presented with an aggressive ulcerative soft tissue mass of 3 months duration in the mandibular molar gingiva. Histologically, the lesion was composed of fibroblastic or myofibroblastic spindle cell proliferations with infiltrative margins in an inflammatory background. Immunohistochemically, the fibroblastic or myofibroblastic spindle cells were positive for vimentin, α-smooth muscle actin, and Ki-67 (MIB-1) but negative for desmin, pan-cytokeratin, S-100 protein, CD34, CD68, CD99, bcl-2, β-catenin, estrogen receptor, progesterone receptor, ALK-1, and p53. These spindle cells were focally and weakly Ki-67- (MIB-1-) positive. The MIB-1 labeling index was 5%. The results of in situ hybridization for Epstein-Barr virus-encoded-RNA were negative. The ratio of IgG4+/IgG+ plasma cells was about 10%. A pathological diagnosis of inflammatory myofibroblastic tumor was made. The postoperative course was uneventful, and the patient has had no recurrence in the 10-year follow-up period. Although no evidence of oral inflammatory myofibroblastic tumor recurrence or malignant transformation has been reported, it has been observed that in inflammatory myofibroblastic tumors of other regions, a prolonged follow-up is necessary after surgical resection. No other case of an IMT patient under 20 years of age has appeared in either the English or the Japanese literature. [ABSTRACT FROM AUTHOR]