PMC9329833_01
Clinical images and panoramic radiograph of the left mandibular lesion of case #1. (A) First visit. Verrucous exophytic, whitish-to-yellowish mass was observed on the left retromolar trigone area. (B) 4 weeks after the first visit and excisional biopsy. Papillomatous lesion, about 3 mm in diameter, recurred on the excision site. (C) 22 weeks after the first visit. There was no remarkable recurred lesion on the left retromolar trigone area. (D) Panoramic radiograph at first visit. Cortical erosion or bony destruction of mandible was not observed below the papillary lesion.
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F1
The lesion was a whitish-to-yellowish verrucous mass on the left RMT area (Figure 1A). Bony destruction was not detected beneath the mass on a panoramic exam (Figure 1D). Four weeks after excision of the lesion, the patient complained about a newly growing mass on the removal site (Figure 1B). Sixteen weeks after the second excision, there was no recurrence on the RMT area (Figure 1C).
Histopathologic examination and molecular pathologic results of surgical specimen of case #1 (classic SialP). (A) Papillary proliferation of surface mucosal epithelium, which is supported by fibrovascular core (Hematoxylin and eosin, x40). (B) Deep portion of tumor is composed of proliferating salivary ductal epithelium (Hematoxylin and eosin, x40). (C) The proliferating ductal epithelium is cuboidal shape with eosinophilic cytoplasm and centric nucleus. It shows papillary folds into the luminal space. Also, there is one layer of flattened cell on the basal side, known as basal cell (Hematoxylin and eosin, x400). (D) The recurrent lesion after first excision showed the same features of ductal proliferation as the previous excised SialP (Hematoxylin and eosin, x40). (E-G) Proliferating ductal epithelium showing positive on CK7(E) and S-100(F). Basal cells are positive on smooth muscle actin (G) (immunohistochemistry staining, x200). (H,I) A few scattered basal cells showed nuclear positive on p53 (H) and Ki-67 (I) in the superficial papillary mucosal epithelium (black arrow), not in the deep adenoma portion (immunohistochemistry staining, x200).
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F2
The superficial exophytic mass was composed of papillary proliferations of keratinized stratified squamous epithelium originated from the mucosa, consistent with a SqP (Figure 2A). The deep portion of the lesion showed proliferations of cuboidal ductal epithelium with eosinophilic cytoplasm, but without nuclear atypia (Figures 2B,C). Immunohistochemical (IHC) staining revealed that the tumorous ductal epithelium in the deep component was composed of cytokeratin 7 (CK7) (+), S-100 (+), smooth muscle actin (SMA) (-) cuboidal cells with surrounding SMA (+) basal cells (Figures 2E-G). Moreover, p53 and Ki-67 protein expression were positive in only a few scattered basal cells of the superficial papillary epithelium on IHC staining (Figures 2H,I). Histopathological examination revealed residual adenoma structures as seen in the first excision (Figure 2D).
PMC9329833_02
Clinical image, histopathologic examination and molecular pathologic results of the surgical specimen of case #2 (SqP mimicking SialP). (A) There was a pinkish exophytic papillary mass on the floor of mouth including lingual frenum. It looked like squamous papilloma, clinically. (B,C) Papillary proliferation of the surface mucosal epithelium supported by fibrovascular core with underlying "superior" hyperplastic ductal structures (asterisks) and "inferior" dilated and tortuous excretory ducts (arrows) (Hematoxylin and eosin, x12.5, x40). (D) Mucosa region: Superficial papillary mucosal epithelium (p) showed mild atypia. The underneath excretory duct is hyperplastic (e) (Hematoxylin and eosin, x100). (E) Superior submucosa regions: hyperplastic epithelium of the excretory duct with microcystic-like changes. There is a layer of ciliated columnar epithelium (luminar layer, arrows) on the hyperplastic squamous stratification (Hematoxylin and eosin, x100). (F) Only the luminal columnar epithelium layer was positive for CK7 staining (Cytokeratin 7, x100). (G) S-100 was diffusely negative in the superior hyperplastic excretory ductal epithelium (S-100, x100). (H) Unlike in SialP, the ductal epithelium was not surrounded by SMA (+) myoepithelial cells, a histologic finding consistent with normal excretory ducts (smooth muscle actin, x100). (I) Minimal p53 and Ki-67 expression were observed in the epithelial basal layer. That is, the atypical proliferation was judged to be a reactive change rather than a precancerous change (immunohistochemistry staining, x400).
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F3
On clinical examination, an exophytic verrucous mass was observed from the floor of mouth to the lingual frenum (Figure 3A). Low-power histopathological examination revealed an exophytic papillary mucosal epithelium with an underlying adenomatous submucosa compartment (Figure 3B). The submucosa compartment was composed of a "superior" hyperplastic and microcystic-like portion and an "inferior" dilated and tortuous ductal portion (Figure 3C). The superficial papillary mucosa had focal atypical features such as bulbous rete ridges and disorganized basaloid proliferation (Figure 3D). In the superior submucosa portion, the overall epithelial structure was adenomatoid, with hyperplastic squamous epithelium overlined by a layer of ciliated columnar epithelium (Figure 3E). In the inferior submucosa portion, indistinct micropapillary-like projections were seen within the dilated columnar ductal epithelium (Figure 3C). IHC staining revealed that CK7 was only positive in the ductal epithelium of the inferior portion and in a single layer of luminal epithelium in the superior submucosa portion (Figure 3F). The superior submucosa portion did not show SMA (+) myoepithelial cells, consistent with a general excretory duct histology rather than the salivary gland tumor, SialP (Figure 3H). The IHC results showed that the Ki-67 proliferation index and p53 expression were minimal and localized at the basal layer in both the lesional epithelium and adjacent normal mucosa (Figure 3I).