Metastatic Carcinosarcoma with a Sarcomatous Predominance?

Abstract Introduction/Objective Uterine carcinosarcoma (CS), also known as Malignant Mixed Müllerian Tumor, is a malignancy characterized by mixed epithelial and mesenchymal components. It is rare and aggressive, most frequently occurring in elderly, postmenopausal women with a median age of 65 years. CS has a tendency to metastasize with an overall poor prognosis. Fine needle aspiration can be useful in identifying metastatic disease, however, demonstration of both sarcomatous and carcinomatous components can be difficult. Methods/Case Report Our patient is a 68 year old female who was first diagnosed with endometrial carcinosarcoma on an endometrial biopsy in 2022. She subsequently underwent a total abdominal hysterectomy with radical dissection, bilateral salpingo-oophorectomy, upper vaginectomy, sentinel lymph node dissection as well as chemotherapy. Immunohistochemistry for MLH1, MSH2, MSH6 and PMS2 all showed intact nuclear expression. Remission was achieved for about a year, after which she was found to have a moderate right sided pleural effusion with right lower lung infiltrates. Also, a right upper lobe mass was reported on chest CT scan. Paracentesis was performed and cytology was consistent with predominantly atypical spindle cells accompanied by a mixed inflammatory infiltrate. Immunohistochemical stains were performed on the cell block, tumor cells were positive for smooth muscle actin, vimentin and negative for desmin, S-100, SOX-10, CD34, P63, TTF-1 and pancytokeratin. Cytology diagnosis was rendered as malignant cells present, consistent with metastatic CS. A subsequent lung mass core biopsy also confirmed the diagnosis. Results (if a Case Study enter NA) NA Conclusion The cytomorphological features in effusion samples from metastatic CS have the carcinomatous component readily identifiable, and only a minority of effusion samples show additional sarcomatous component. The exact diagnosis of CS may not be possible due to the absence of sarcomatous components. Alternatively, as we present in this rare case of metastatic CS, the sarcomatous component in the form of abundant atypical oval to spindle cells with hyperchromatic nuclei may be the only form of malignant cells present in the specimen. Careful morphological assessment of architectural patterns, a good past medical history, availability of cell blocks and immunohistochemistry are vital in providing an accurate diagnosis in such rare cases of metastatic CS.