Mature cystic teratoma (MCT), a benign tumour commonly called the dermoid cyst, is the most common type of ovarian germ cell tumours. Malignant transformation (MT) is a rare and the worst complication of MCT that occurs in 1–3% of cases, especially postmenopausal women. Since the incidence of malignant transformation is very low, the clinical presentation, management and prognostic factors are not well understood still. It is important to determine the clinical, radiological and pathological characteristic of malignant transformation of mature cystic teratoma to squamous cell carcinoma. Here, we present a case of 33-year-old multiparous lady with mature cystic teratoma with unusual presentation with histopathological diagnosis of squamous cell carcinoma of mature cystic teratoma.

A 33-year-old multiparous lady presented with the complaints of recurrent high grade, burning micturition for the past 2 months. Initially, she was admitted and evaluated in another hospital for the same, underwent thorough workup for recurrent fever. She was incidentally detected with the left ovarian cyst. Her serum tumour marker levels were within normal limits. MRI abdomen and pelvis was suggestive of the left ovarian dermoid cyst, and malignant transformation cannot be ruled out. The decision of surgical management with excision of ovarian mass was taken after discussing with the patient and family members. Intra-operatively, the left ovarian mass of 140 × 120 mm was noted with no surface deposit, adherent to bladder and omentum. Ovarian mass was infiltrating bladder wall full thickness up to mucosa. Sigmoid serosa deposits were also seen. The left ovarian tumour, fallopian tube was excised along with partial cystectomy (full-thickness bladder with wide margin excised followed by primary closure with suprapubic catheter (SPC) insertion). Specimen was sent for frozen section and was reported as dermoid tumour with malignancy. Hence, we proceeded with complete staging procedure which included hysterectomy, right salpingo-oophorectomy, complete pelvic and para-aortic lymph node dissection (up to the level of the left renal vein), complete omentectomy and excision of sigmoid colon deposits. Post-operative period was uneventful. Histopathology examination revealed dermoid with malignant tumour—squamous cell carcinoma, Stage IIIC. She is undergoing adjuvant chemotherapy now.

Malignant transformation in mature cystic teratoma is a rare condition. There is no standard treatment as the incidence is low. The current recommendation according to various studies is to proceed with complete staging surgery followed by chemotherapy, similar to epithelial ovarian cancer. The prognosis in the patients with advanced disease is poor.