Posttraumatic lipoma

Giant inframuscular lipoma disclosed 14 years after a blunt trauma: a case report

INTRODUCTION

Lipoma is the most frequent benign tumor of the soft tissue. This lesion is often asymptomatic except in cases of enormous masses compressing nervous-vascular structures. Although the diagnosis is mostly clinical, imaging tools are useful to confirm the adipose nature of the lesion and to define its anatomic border. Sometimes, lipomas may be the result of a previous trauma, such as in this patient.

CASE PRESENTATION

A 45-year-old man presented at our institution with a giant hard firm mass in the upper external quadrant of the right buttock disclosed after a weight loss diet. Subsequent magnetic resonance imaging showed a giant adipose mass developed beneath the large gluteal muscle and among the fibers of the medium and small gluteal muscles. When questioned on his medical history, the patient reported a blunt trauma of the lower back 14 years earlier. He underwent surgery and histological examination confirmed a giant lipoma.

CONCLUSION

Lipomas might result from a previous trauma. It is hypothesized that the trigger mechanism is activated by cytokine and growth factors released after the trauma. We herein present an exceptional case of a giant post-traumatic lipoma which caused a painful compression on the right sciatic nerve.

Diagnostik und Therapie posttraumatischer Pseudolipome

BACKGROUND

Both trauma and lipomas are frequently encountered in day-to-day clinical practice. Although lipomas are defined both clinically and pathologically as benign fatty tissue tumours, their aetiology is still not clear.

METHODS

In this study 19 patients with 23 posttraumatic lipomas were analysed retrospectively with reference to ultrasound and MRI diagnosis, history, laboratory results and histopathological investigations.

RESULTS

The mean age of the patients was 50.5 years (+/-15.5). The causative soft tissue trauma dated back an average of 2.6 years. When the histories were taken, 16 of the 19 patients reported vast, slow-resorbing posttraumatic haematomas. Nine of the 23 lipomas were sited in the upper extremity, 3 in the lower extremity, 9 in the trunk and 2 in the face. All were located epifascially. In 22 cases the lipomas were excised, and in 1 case the lipoma was removed by liposuction. Histological examination demonstrated capsulated benign fatty tissue tumours in 19 cases and uncapsulated benign fatty tissue tumours in 4. The average body mass index (BMI) was 29 kg/m(2). Removal of the tumour resulted in a good aesthetic result in all patients.

CONCLUSIONS

The link between a blunt soft tissue injury and the development of a posttraumatic lipoma is still the subject of controversy; there are two mechanisms that seem more likely than any others proposed: (1) the "pseudolipoma" as the result of a prolapse of fatty tissue as an immediate result of trauma and (2) the development of a lipoma by way of differentiation of pre-adipocytes mediated by cytokines released by a posttraumatic haematoma. There appears to be a correlation between an increased partial thromboplastin time (PTT) and the development of posttraumatic lipomas. The generalised increase in the volume of body fat documented by the elevated BMI supports the idea that lipomas arise from the prolapse of adipose tissue. However, there is no single mechanistic explanation for the development of posttraumatic lipomas. They are probably caused by multiple factors and not by isolated pathological mechanisms.