Figure 3.

Transformation of spiradenoma into spiradenocarcinoma: (a) benign spiradenoma exhibits a dense nodular arrangement of myoepithelial and epithelial cells, intermingled with scattered lymphocytes (×100); (b) SOX10 immunohistochemistry diffusely and intensely stains the nuclei of spiradenoma, similar to adenoid cystic carcinoma (×100); (c) malignant transformation of a spiradenoma (right) into a spiradenocarcinoma (left): the malignant component demonstrates loss of architecture, pleomorphism, necrosis, cell crowding, increased mitotic activity, and loss of lymphocytic infiltrate (×100); (d) Ki67 immunohistochemistry: the labeling index is higher in the spiradenocarcinoma (left) compared to the precursor spiradenoma (right) (×100).