Fig. 5

Pathological findings in the surgically resected specimen. On gross viewing, a protruded lesion with an ulcerated surface was observed in the gingiva of the left molar region (A). On the cut surface of the specimen (B, left panel), a whitish solid tumor invading the mandibular bone was evident; the right panel shows loupe view of hematoxylin and eosin staining of the specimen. Furthermore, hematoxylin and eosin staining (C–E) revealed that most of the lesion consisted of conventional squamous cell carcinoma (SCC) forming solid nests with obvious keratinization (C). There were typical spindle cells containing pleomorphic nuclei observed adjacent to the conventional SCC foci (D) as well as atypical spindle cells that often incorporated neutrophils within their cytoplasmic vacuoles (E). Immunoperoxidase staining showed neutrophil elastase expression (F), as well as intense LAMP-1 (G) and cathepsin B (H) mainly localized around the vacuoles that contained the neutrophils. Panels E–H show serial sections. Scale bars: 10 mm (B), 500 μm (C), 200 μm (D), 50 μm (E–H), and 10 μm (inset in E–H)