Carcinoma cells can lose their epithelial cell characteristics and dedifferentiate into a fibroblast-like cell during progression of a neoplasm. Aberrant expression of oligomeric transcriptional complexes contributes to progression of carcinomas. Although individual transcription factors initiating progression remain unknown, LIM-only protein (LMO) and LIM-domain binding protein (LDB) negatively regulate breast carcinoma cell differentiation. In this study, we investigated the expression of LMO4 and LDB in squamous cell carcinomas of the oral cavity. LMO4 mRNA was amplified in four of six carcinoma tissues and eight of 12 carcinoma cell lines, and LDB1 in three carcinoma tissues and 11 cell lines examined. Immunoprecipitation studies revealed that LMO4 and LDB1 interact with each other in the nuclear milieu of the carcinoma cells indicating the presence of an LMO4-LDB1-mediated transcription complex. Both LMO4 and LDB1 proteins were preferentially localised in the nuclei of carcinoma cells at the invasive front and the immunoreactivity was increased in less-differentiated carcinoma tissues (Po0.01). Carcinoma cells metastasised to the cervical lymph nodes with increased immunoreactivity compared to the primary site of neoplasm (Po0.05). These data suggest that the LMO4 -LDB1 complexes may be involved in carcinoma progression possibly through dedifferentiation of squamous carcinoma cells of the oral cavity.

Inverted ductal papilloma (IDP) is a type of ductal papilloma arising in ducts of minor salivary glands. Very few cases, and no cases in Japan, have been reported. Reported herein is a case of IDP with a review of the literature. The patient was a 49-year-old man presenting with a lump in the right buccal mucosa of the premolar area of the mandible. The tumor was excised en bloc after a biopsy diagnosis of IDP. On the surface of the covering epithelium, an opening was seen to be filled with mucinous material. On cut surface the opening led to the tumor cavity. The major portion of the tumor parenchyma was made up of papillary proliferation of basaloid squamous cells. Some crypts, microcysts, and mucous cells were seen. There were no findings suggestive of a malignant tumor. The patient's postoperative course was uneventful and there has been no recurrence after 1 year's follow up. Immunohistochemical analysis of the present case supports the hypothesis that IDP originates from squamous metaplasia and proliferation of minor salivary gland duct cells.

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