A 9-year-old girl consulted to our hospital because of lower lip
tumor. Excision of the
tumor was performed. Histologically, the
tumor consisted of cellular spindle and round cells with hyperchromatic nuclei and nucleoli. Mitotic figure and apoptotic bodies were scattered. Immunohistochemically, the
tumor cells were strongly and diffusely positive for CD10 and
vimentin. The
tumor was focally positive for
S100 protein, α-smooth muscle actin, PDGFRA, HER2/neu, p53, and CD68. The Ki-67 labeling was 20%. In contrast, the
tumor cells were negative for pancytokeratins (AE1/3,
CAM5.2, WSS, KL-1, HNF116),
cytokeratin (CK) 5/6, CK34βE12, CK7, CK8, CK14, CK18, CK19, CK20, EMA,
desmin, CD34, melanosome, KIT, p63,
myoglobin, CD45, CD56, GFAP, D2-40, CEA and
synaptophysin. The Histologies, positive p53
protein, and Ki-67 labeling of 20% suggested low grade
malignancy. Although histological type was unclear, the author diagnosed this
tumor as malignant
myoepithelioma arising from the lip minor salivary gland because of positive reaction for
S100 protein, α-smooth muscle actin, and CD10. The patient is now free from
tumor 8 years after the first presentation.