Undifferentiated Endometrial Carcinoma—Diagnostic and Therapeutic Challenges

Abstract Undifferentiated/dedifferentiated endometrial carcinoma is clinically highly aggressive, particularly when it is defined by inactivation of core SWI/SNF proteins (co-loss of ARID1B, loss of SMARCA4, or loss SMARCB1 expression). We report here the case of a 37-year-old woman who presented with menorrhagia and the subsequent pathologic and clinical workup showed an advanced-stage ARID1A/ARID1B-deficient mismatch repair–proficient undifferentiated endometrial carcinoma. Despite pelvic external beam radiation and platinum/taxane-based chemotherapy (4 of 6 planned cycles), the patient experienced disease progression with osseous metastasis to her left elbow and died of her disease 7 months after clinical presentation. This case highlights the diagnostic and treatment challenges associated with such undifferentiated/dedifferentiated cancer types of the endometrium.