NMA/AGSM/2025/PUBH/001-Ovarian collision tumour: Serous Cystadenoma and adipocyte rich mature cystic teratoma.

Collision tumour refers to the simultaneous coexistence of two distinct tumors in the same tissue or organ without any transition zone or mixing interface. Collision tumors have been described in various body organs. However, their occurrence in ovary is rare. and mature cystic teratoma with prominent adipocytic proliferation is also an exceedingly uncommon finding. Mature cystic teratoma is the most common component of collision combinations. We present a case of a 20-year-old P0+0 who presented with complaints of a 2-year history of abdominal swelling that was initially small but gradually increased to present size. Her medical history was non-contributory. The Ultrasonography findings revealed: Huge intra-abdominal cystic mass with differentials of Pancreatic Pseudocyst, Mesenteric and Simple Ovarian cysts. Physical examination and vital sign were within normal limit. Abdomen was distended with abdomino-pelvic swelling of about 32 weeks size. The ovarian specimen measuring 22× 12×12 cm with a weight of 4100g, and a bi-loculated solid and cystic area filled with 3000mls amber colour fluid was found. The solid area showed tufts of hair and yellowish materials. Histological sections revealed fibro collagenous cyst wall lined by Tubal type of epithelium and areas showing keratinized squamous epithelium with skin adnexa and predominantly adipose tissue. A diagnosis of collision tumour comprising of mature cystic teratoma with prominent adipocytic tissue and serous cystadenoma was made. Collision tumours present a complex clinical scenario that demands extensive tissue sampling of cystic ovarian masses for a comprehensive diagnosis, so as not to miss any component which might have a bearing on prognosis of the patient.