Epithelial-myoepithelial carcinoma with high grade transformation.

Epithelial-myoepithelial carcinoma (EMC) is a rare low-grade salivary gland malignancy of presumed intercalated duct origin comprising 1% of all salivary gland tumours. High grade transformation (HGT) in EMC is a recently recognised entity with only a few cases reported in the literature. The authors report an additional case of EMC with HGT involving the submandibular gland. The patient was a 60-year-old woman who requested examination of the rapid growth of a mass in the left submandibular area, which she had first noticed 20 years previously. Histologically, the tumour had two distinct carcinomatous components. One component had features of a low grade EMC. The second component consisted of polygonal cells, arranged in a solid and nested pattern, with marked nuclear pleomorphism, brisk mitotic activity, and frequent necrosis. The Ki-67 labelling index of the EMC component was 9%, and that of the high grade component was 40%. The patient developed multiple pulmonary metastases 15 months after surgery. The aggressive behaviour of EMC with HGT suggests that it is important to recognise this variant of EMC to avoid misdiagnosis and inappropriate treatment.