PLAG1 overexpression in salivary gland duct-acinar units results in epithelial tumors with acinar-like features: Tumorization of luminal stem/progenitor cells may result in the development of salivary gland tumors consisting of only luminal cells.

OBJECTIVES: Details about salivary gland tumor histogenesis remain unknown. Here, we established a newly generated murine salivary gland tumor model that could overexpress pleomorphic adenoma gene 1 (PLAG1) and attempted to clarify the events that occur during the early phase of salivary gland tumor histogenesis. METHODS: Salivary gland tumors were generated using murine models (Sox9IRES-CreERT2; ROSA26-PLAG1). Lineage tracing of Sox9-expressing cells was performed using Sox9IRES-CreERT2; ROSA26-tdTomato mice, which were generated by crossing Sox9CreERT2/- and ROSA26-tdTomato mice (expressing the tdTomato fluorescent protein). Organ-cultured embryonic salivary glands from the murine model were morphologically analyzed, and mRNA sequencing was conducted two days after tumor induction for gene enrichment and functional annotation analysis. RESULTS: Salivary gland tumors exhibited epithelial features with acinar-like structures because of gene rearrangements in the luminal cells. Structural disturbances in the duct-acinar unit of the salivary gland were observed and cancer-related pathways were enriched among the differentially upregulated genes in the early phase of tumor induction in an organ-cultured embryonic salivary gland tumor model. CONCLUSIONS: The newly generated murine salivary gland tumor model may show that the tumorization of luminal stem/progenitor cells can result in the development of salivary gland tumors comprising only luminal cells.

Rare papular presentation of an elastofibromatous lesion of the alveolar mucosa.

A 72-year-old Japanese female patient presented with an asymptomatic, white-colored, smooth-surfaced, firm papule 3 mm in diameter involving the mucosa on the posterior part of the right maxilla. An excisional biopsy specimen was diagnosed as an oral focal submucous elastofibromatous lesion. A review of the literature revealed very few documented cases of oral mucosal lesions characterized by accumulation of degenerated elastic fibers. Various oral lesions have histopathological features similar to those observed in cutaneous diseases, and the present case was a focal submucous elastofibromatous lesion in the alveolar mucosa.