Huang A, et al. - Researchers assessed the importance of histologic characteristics in facilitating the diagnosis of atypical spiradenoma and spiradenocarcinoma. They noticed an sudden transformation from benign to malignant morphology, nuclear atypia, atypical mitotic figures, and a monomorphic loss of the dual cell population. About 85.7% of cases also had dilated vessels, and 71.4% had ductal dilation/proliferation. They noted 43% of cases had tumor encapsulation, 43% had massive necrosis, and 14% had focal cellular necrosis. They observed histologic traits that indicate atypical spiradenoma or spiradenocarcinoma, like an sudden transformation to malignant foci, atypical mitotic figures, and monomorphic loss of the dual cell population. They found Ki-67, p53, and S100 helpful in demarcating the regions of atypical or malignant transformation in spiradenomas.