Description

A 60-year-old man presented with a painful, enlarged palpable mass in the left iliac fossa. A CT scan of the abdomen and pelvis demonstrated a large heterogeneous mass extending through the abdominal wall musculature (figure 1), which was suspected to be an atypical lipomatous tumour (ALT) or well-differentiated liposarcoma (WD-LPS).

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Figure 1

Lipoma passing through the abdominal wall musculature.

Intraoperatively, a large firm lipomatous mass was noted in close proximity to the left spermatic cord. It extended into the retroperitoneal space and transgressed the internal oblique to lie deep to the external oblique aponeurosis, adopting an unusual ‘dumbbell’ shape. Due to clinical uncertainty as to whether the mass was simply in close proximity to the spermatic cord or a cord liposarcoma, a left radical orchidectomy was performed en bloc with the tumour.

Lipomas are the most common soft tissue mesenchymal tumour,1 and are histologically benign. It is highly unusual for them to pass through tissue planes. Lipomas lack MDM2 amplification on cytogenetic testing; unlike ALTs and WD-LPSs which are locally progressive, have a propensity to recur and require specialist management. The terms ALT and WD-LPS are synonymous as these tumours are morphologically and karyotypically identical.1 ALT describes lesions in superficial sites and extremities2 which are more amenable to complete surgical resection with a wide margin. WD-LPS describes lesions arising in the retroperitoneum, mediastinum and deep pelvis—locations that are less amenable to radical excision due to surrounding structures. Nagano et al 2 have devised a scoring system to differentiate lipomas and ALTs using MRI characteristics: diameter, depth, septa and fat saturation enhancement. The system appears promising, but requires further validation.