Atypical metastatic pattern of thigh myxoid liposarcoma

We present the case of a 70-year-old male patient with a history of thigh myxoid liposarcoma, sent to our establishment for a CT scan as a part of a follow-up evaluation.

The CT scan revealed multiple metastases in atypical locations, all presenting with similar imaging features. These hypoattenuating formations were identified in various regions: intracardiac (right and left ventricles), mediastinal (posterior mediastinum) (Figure 1), intraperitoneal (splenogastric space and left flank) (Figures 2 and 4), parietal (left abdominal wall) (Figure 3), and in the right scrotum (Figure 5).

Soft tissue sarcomas are rare tumours, comprising 0.7% of all adult malignancies. Liposarcoma is a mesenchymal malignant tumour originating from adipose tissue and can be subclassified into well-differentiated, myxoid, round cell, pleomorphic, and dedifferentiated types. Well-differentiated and myxoid tumours tend to be low-grade with fewer metastases, whereas other histological subtypes present a more invasive profile with a higher metastatic incidence rate [1].

Extremity soft tissue sarcomas typically metastasise to the lungs, but can demonstrate a unique extrapulmonary metastatic pattern. Myxoid liposarcoma, in particular, has a distinct pattern of metastatic spread, favouring extrapulmonary sites such as soft tissue, retroperitoneum, chest and abdominal wall, peritoneal surface, skeleton, and heart [2]. Several studies speculate that the reason behind this specific metastatic spread can be explained by the abundance of fatty tissue in these secondary localisation sites, including subcutaneous tissue, peritoneum, bone marrow, and the epidural space [3].

In this report, we present the case of a lower limb myxoid liposarcoma, a subtype that represents 40% of all liposarcomas of the extremities. The appearance of a myxoid liposarcoma depends on the amount of fat and myxoid tissue. It generally shows a homogeneous low signal on T1 with high-signal foci, a high signal intensity on T2 and variable enhancement based on the cellularity and vascularity of the tumour [3]. In some cases, the tumour appears cystic. Metastases often present a hypodense appearance due to mucinous material, as observed in our patient [4].

The follow-up studies should include a chest, abdominal and pelvic CT, or even a whole-body MRI. Recent studies showed the superiority of this imaging modality in detecting extrapulmonary metastases, especially when it comes to skeletal lesions that are often missed in conventional imaging modalities [5]. However, it remains to be determined whether these findings represent metastases of myxoid liposarcoma or a metachronous disease affecting various locations [6].

The treatment management includes primarily a surgical excision of the tumour with or without adjuvant radiotherapy and chemotherapy. The decision relies entirely on the risk of recurrence. A myxoid liposarcoma is considered to present a poor prognosis and a higher risk of extrapulmonary metastases in case of a large tumour, a high histological grade, and the presence of tumour necrosis [6].