Uterine Carcinosarcoma Presenting as Metastatic Osteosarcoma in the Lung: A Case Report and Literature Review.

Uterine carcinosarcomas (UCS) are aggressive tumors characterized by their biphasic nature, consisting of high-grade epithelial and mesenchymal elements. One component may predominate over the other. We present the case of a 59-year-old female who initially received a diagnosis of endometrial serous carcinoma and presented one year later with a malignant neoplasm in the lung featuring osteosarcomatous differentiation. Notably, the bone scan did not reveal any evidence of a primary bone tumor. However, additional sampling from the endometrium demonstrated a UCS with an osteosarcomatous component.Upon reviewing existing literature, it has been observed that metastases in carcinosarcoma cases generally arise from the carcinomatous component. Conversely, the sarcomatous component typically spreads locally to areas such as the vagina, cervix, or fallopian tubes. The presented case stands out as a unique instance of an undiagnosed UCS manifesting as metastatic osteosarcoma in the lung. This case underscores the complexity and diverse presentations of UCS and emphasizes the importance of comprehensive evaluation in understanding its clinical manifestations.