Large pelvic mass reveals poorly differentiated carcinoma with sarcomatoid dedifferentiation: a diagnostic and surgical challenge.

Sarcomatoid carcinoma is a rare and aggressive malignancy characterised by a combination of epithelial and mesenchymal features, often complicating the identification of its primary origin. These tumours can arise in various anatomical sites, including the gastrointestinal tract and pelvis, and are typically associated with rapid growth, local invasion and a poor prognosis. We present the case of a woman in her mid-60s with a history of total abdominal hysterectomy and bilateral salpingo-oophorectomy for benign disease, who developed a large pelvic mass. Initial imaging revealed an extensive, heterogeneous lesion measuring 12 cm in diameter, involving adjacent structures. Surgical exploration demonstrated the tumour's extensive adherence to surrounding tissues, necessitating ileocolic resection and omentectomy. Histopathological analysis confirmed a poorly differentiated carcinoma with sarcomatoid dedifferentiation, while immunohistochemical studies were inconclusive regarding the primary origin. This case underscores the diagnostic and therapeutic challenges posed by sarcomatoid carcinoma, highlighting the importance of a multidisciplinary approach and the role of molecular studies in optimising management.