Fig. 1

Magnetic resonance imaging before and after first surgery and histopathological images. a–d A single large, cystic mass is invading the parietal bone bilaterally and shows attachment to the superior sagittal sinus without occlusion. The tumor measures 41 × 42 × 34 mm (a sagittal view; b coronal view). The cystic lesion is resected, preserving the superior sagittal sinus and dura. The cranium and scalp are reconstructed with titanium mesh and local pedicled skin flap (c sagittal view; d coronal view). e–h Histopathological images obtained from first surgery. Hematoxylin and eosin staining demonstrates that glandular lumens and ducts are forming palisading or solid nests. Bar = 50 μm (e). Two distinct cell types, with eosinophilic cuticular cells (yellow arrows) surrounded by poroid cells with a high nuclear-cytoplasmic ratio (black arrows) are shown. Overall cytoplasmic atypia, some mitotic figures (black arrowhead) and partial loss of the two-cell structure are also observed, compatible with low-grade spiradenocarcinoma. Bar = 25 μm (f). Immunohistochemistry shows broad expression of cytokeratin 7. Bar = 50 μm (g). Ki-67 labeling index is approximately 30%. Bar = 50 μm (h). The histopathological images are obtained using the Olympus BX51 microscope and Olympus DP21 digital microscopy camera (Olympus Corporation, Tokyo, Japan).