Ichthyosis Uteri Mimicking Endometrial Cancer with Apparent Myometrial Invasion

Ichthyosis uteri is a rare benign condition characterized by extensive squamous metaplasia of the endometrium. We present an unusual case of ichthyosis uteri with radiological features mimicking myometrial invasion of endometrial cancer, occurring in a 50-year-old postmenopausal woman who presented with persistent abnormal vaginal bleeding. Laboratory findings revealed elevated serum squamous cell carcinoma (SCC) antigen level of 11.5 ng/mL. Magnetic resonance imaging (MRI) demonstrated an intrauterine lesion with apparent myometrial invasion, initially suggesting the International Federation of Gynecology and Obstetrics stage IA endometrial cancer. The lesion showed low signal intensity on the T2-weighted image compared to normal endometrium and weak enhancement on the contrast-enhanced T1-weighted image. While the lesion showed high signal intensity on diffusion-weighted imaging, the apparent diffusion coefficient value (0.96 × 10^-3 mm²/sec) indicated no substantial diffusion restriction. Despite the biopsy showing only squamous metaplasia without malignancy, a total hysterectomy was performed due to persistent bleeding, elevated serum SCC antigen level, and suspected myometrial invasion. Pathological examination revealed extensive papillary proliferation of bland squamous epithelium extending along adenomyosis, with concurrent endometrial hyperplasia. Postoperative serum SCC antigen level normalized to 0.7 ng/mL. This case highlights a unique radiological presentation of ichthyosis uteri, where extension along adenomyotic foci mimicked myometrial invasion of endometrial cancer. The relative lack of diffusion restriction on MRI, despite the lesion's size, may serve as a valuable diagnostic clue in differentiating ichthyosis uteri from endometrial cancer.