case_images: PMC11234147_01
case_images: MRI findings for Case 1. (A) T2WI showed that the lesion was located in the deep lobe of the parotid gland, with a round shape and mixed long T2WI signals. There were multiple short T2WI signals on the interior, and short T2WI signal rings, which were locally discontinuous, were seen at the edge of the lesion. (B) The lesion was iso-/slightly short on T1WI, with a long T1WI signal ring, which was locally discontinuous, at the edge of the lesion.
case_images: fonc-14-1391616-g001.jpg
case_images: PMC11234147_01_fonc-14-1391616-g001.jpg
case_images: f1
case_images: Septation enhancement was noted within the mass, and localized incomplete capsule formation was observed ( Figure 1 ).
case_images: Microscopic features of Case 1. (A) The tumour was well defined; (B) Under a low-magnification microscope, the tumour exhibited polycystic structure. The cyst wall was lined with stratified epithelium, and the subepithelial stroma demonstrated dense lymphocytic arrangement, forming lymphoid follicles; (C) Epithelial cells, polygonal in shape with eosinophilic cytoplasm, exhibited a crowded pattern devoid of obvious polarity. Scattered mucus cells were interspersed in the epithelium; (D) Nested epithelial hyperplasia was evident in some areas, consisting of squamoid cells, mucous cells and intermediate cells; (E) Immunohistochemistry demonstrated positive expression of CK7 in the epithelial components; (F) FISH indicated the fusion signals of the MAML2/CRTC1 gene (arrow).
case_images: fonc-14-1391616-g002.jpg
case_images: PMC11234147_01_fonc-14-1391616-g002.jpg
case_images: f2
case_images: Histologically, the tumor exhibited well-defined and complex cystic architecture ( Figure 2A ). The cyst wall was lined with stratified epithelium, and the subepithelial stroma demonstrated densely arrangement of lymphocytes with formation of lymphoid follicles ( Figure 2B ). Scattered mucus cells were interspersed in the epithelium ( Figure 2C ). In some areas, sheet-like epithelium hyperplasia was observed, comprising squamoid cells, mucous cells, and intermediate cells ( Figure 2D ). Immunohistochemistry demonstrated positive expression of CK7, CK8, and CK18 in the epithelial components ( Figure 2E ). Fluorescence in situ hybridization (FISH) revealed MAML2/CRTC1 gene fusion ( Figure 2F ).
case_images: PMC11234147_02
case_images: Microscopic features of Case 2. (A) The tumour had a clear boundary; (B) The polycystic appearance under a low-magnification microscope. The lesion presented an epithelial lining and multiple cysts within a backdrop of dense lymphoid stroma; (C) The stratified, nonpolar epithelium interspersed with mucus-secreting cells was evident; (D) Proliferation of epithelial cells in some regions formed nests, comprising squamoid, intermediate, and mucinous cells; (E) P63 immunohistochemical staining highlighted squamoid cells and intermediate cells; (F) FISH showed the fusion signals of the MAML2/CRTC1 gene (arrow).
case_images: fonc-14-1391616-g003.jpg
case_images: PMC11234147_02_fonc-14-1391616-g003.jpg
case_images: f3
case_images: Macroscopic examination unveiled a well-defined grey-yellow nodule with a 2 cm diameter, exhibiting clear demarcation ( Figure 3A ). Microscopically, the lesion shared similarities with the previously described Case 1, presenting an epithelial lining and multiple cysts within a background of dense lymphoid stroma ( Figure 3B ). The epithelium was stratified, nonpolar, and interspersed with mucus-secreting cells ( Figure 3C ). Proliferation of epithelial cells in some regions formed nests, comprising squamoid, intermediate, and mucinous cells ( Figure 3D ). Immunohistochemically, epithelial components expressed CK7, while squamoid cells and intermediate cells expressed P63, P40, and CK5/6 ( Figure 3E ). FISH revealed fusion of MAML2/CRTC1 ( Figure 3F ).