A Rare Case Report on Dedifferentiated Liposarcoma of the Thigh Mimicking an Abscess With Vascular Features: A Diagnostic Challenge With Fatal Outcome.

Dedifferentiated liposarcoma (DDLPS) is an aggressive malignant soft tissue tumor comprising approximately 15%-20% of all liposarcomas. When presenting in the extremities, its atypical clinical and radiological features may mimic vascular or infectious conditions, posing a serious diagnostic challenge that can delay curative intervention. A 60-year-old diabetic female presented with a 6-month progressive left thigh mass accompanied by intermittent fever, significant weight loss, and refractory anemia. Doppler ultrasonography initially suggested a hemangioma; contrast-enhanced CT was interpreted as an organized abscess. Ultrasound-guided aspiration yielded 600 mL of thick necrotic aspirate-Gram stain demonstrated no organisms, culture was sterile, and aspirate cytology showed RBC 98,000 and WBC 25,000, confirming the absence of pyogenic infection. Concurrent core biopsy from the lesion wall established the diagnosis of DDLPS (FNCLCC Grade 2). PET-CT confirmed locoregional disease without distant metastasis. Following surgical referral, the patient died suddenly overnight before planned excision. To our knowledge, this is the first reported case demonstrating the combined triad of Doppler-based vascular mimicry, CT-based abscess diagnosis, and large-volume sterile necrotic aspirate in extremity DDLPS, culminating in sudden pre-operative death. This case highlights that histopathological evaluation-including concurrent biopsy of any aspirated deep soft tissue mass-must not be deferred regardless of apparent microbiological findings.