Preferential human epidermal growth factor receptor 2 expression in myometrial and lymphovascular invasion of a uterine carcinosarcoma: A case report

This case report describes a unique pattern of human epidermal growth factor receptor 2 expression in a patient with uterine carcinosarcoma. The endometrial tumor showed biphasic morphology composed of serous carcinoma and a heterologous high-grade sarcoma component. Human epidermal growth factor receptor 2 immunostaining showed positive (3+) expression in foci of myoinvasion, lymphovascular invasion, and lymph node metastasis but was negative in both the endometrial surface tumor and sarcomatous component. Fluorescent in situ hybridization testing for human epidermal growth factor receptor 2 confirmed no amplification within the endometrial surface carcinoma component and amplification of the lymphovascular invasion component. As the use of human epidermal growth factor receptor 2 immunohistochemical evaluation becomes more commonplace for therapeutic consideration in patients with uterine carcinosarcoma, interpretation of the immunohistochemical should be performed preferentially on large tissue sections including both a surface, myoinvasive portions, and suspected areas of lymphovascular invasion and lymph node metastasis.