Excision of a massive lipoma of the thigh following extensive weight loss and bariatric surgery

Background

Lipomas are benign tumours which arise from adipose tissue. Typically, they are well encapsulated and on examination are typically soft and mobile, without tethering to the overlying skin. Lipomas can occur anywhere in the body and are usually asymptomatic when small. Management can be conservative or surgical excision.1 Liposarcoma may present in a similar fashion to that of lipoma and have potential for metastatic spread. Imaging modalities can be used to assess the size of lipoma or liposarcoma, but importantly, should not be used to determine whether the lesion is benign or malignant.2 In order to differentiate between benign and malignant, histopathology and genetic markers are important. MDM2 is a key gene encoding an inhibitor protein, p53 and is present in liposarcoma. This case describes a giant lipoma of the left medial thigh. A giant lipoma is defined as being greater than 1 kg or greater than 10 cm.2 Giant lipomas develop over several years and can be located anywhere on the body. We highlight that this patient was morbidly obese and despite massive weight loss, there was no change in the size of the medial thigh mass and ultimately, operative management was necessary. It was important to plan operative management by obtaining MRI images first, allowing us to determine the extent of involvement of the mass and which neurovascular structures were within or in close proximity. Additionally, we describe the importance of differentiating the medial thigh mass from lipoma or liposarcoma as this would affect the type of treatment offered postoperatively.

Case presentation

We present a 52-year-old bariatric patient with a body mass index (BMI) of 78 kg/m², weighing 244 kg in February 2012. He was referred by his general practitioner for consideration of bariatric surgery. The patient gave a history of obesity since childhood, his poor mobility was severely impaired and he wanted help to return to a normal life.

With a medical history of depression, atrial fibrillation, obstructive sleep apnoea, chronic venous insufficiency and his severely high BMI, it was felt that he was not fit for surgery and referred onto the nutrition clinic for weight loss programme.

By the time of assessment in September 2013 in the clinic, his weight had increased to 264.1 kg. At the clinic, it was discussed that he would need to reduce BMI to around 60 for consideration of bariatric surgery. A Protein Sparing Modified Fast diet was commenced, and after 4 months he had reduced his weight by 28.2kg to 235.9 kg. During this diet, he was supplemented with forceval. It was apparent that the patient was not very compliant with the Protein Sparing Modified Fast diet, and 15 months later, had gained 27.5 kg, weighing 263.4 kg. It was decided after this weight gain and poor attendance at clinics that he would not be for weight loss surgery and was discharged from the nutrition clinic. Throughout this period of time, a large swelling of the left thigh was noted by medical staff and the patient commented that it had been present for several years. The mass limited his mobility, made it difficult for him to maintain good hygiene and was prone to sores developing with associated cellulitis.

No prior investigation of the mass was arranged and no underlying cause of chronic venous insufficiency investigated in the past. However, the duration of chronic venous insufficiency dated to before the appearance of the medial thigh mass.

One year later, he was admitted to hospital with cellulitis of a large medial thigh swelling and managed with intravenous antibiotics. BMI at this time was 96.7, 303 kg. While an inpatient, he was reviewed by the consultant biochemist and agreed to be commenced on the Counterweight Plus Programme which consisted of liquid diet and would continue while being an inpatient. Over a 6-month period, as an inpatient and strictly adhering to the Counterweight Plus Programme, he reduced his weight to 177.2 kg, BMI 56 kg/m².

Subsequently, a laparoscopic sleeve gastrectomy was performed in November 2016 without complications and Counterweight Plus Diet programme continued for another 2 weeks postoperatively.

The patient’s weight remained stable following bariatric surgery, however, the left medial thigh mass never reduced in size. This impaired mobility, was prone to infection and was of discomfort. He was reviewed by the plastic surgeons regarding removal of the large mass. MRI scan showed a 37 ×23 ×23 cm swelling of oedematous fatty tissue with the great saphenous vein passing through the mass. Femoral and inguinal herniae were excluded but sarcoma could not be excluded. During the interval period between 2016 and 2018, there was discussion with the patient regarding management of the medial thigh mass, however, with several clinic appointments not attended by the patient, there was a delay in seeing him in order to plan an operation and for him to be seen in a preoperative assessment clinic. In 2017, a clinic appointment was made with plastic surgeons and it was felt at the time, the mass was consistent with lymphoedema and an MRI scan was arranged to investigate this. As nothing sinister was reported on the MRI scan, the patient was listed for surgery to excise the mass.

In November 2018, plastic surgeons excised a 10 kg lipomatous mass from the left medial thigh with direct closure of the skin (figure 1). Anterior and posterior skin flaps were raised and the central portion of skin overlying the pendulous mass excised. The long saphenous vein and its tributaries were identified within the mass and ligated. Two 15 f drains were inserted and skin closed with 3–0 monocryl deep dermal and subcuticular. Wound glue, Prevena and wool crepe were used as dressings.

Pathology revealed a 58 ×42 ×18 cm mass with multiple sinuses extending from the skin surface, grossly oedematous fat and a deep conglomerate of benign-appearing lymph nodes. Microscopically, there was evidence of chronic inflammation, epidermal inclusion cysts and ectasia of lymphatics. The pathological conclusion was a massive localised lymphoedema arising within a background lipoma. Molecular cytogenetic analysis was also undertaken, with no evidence of MDM2 amplification, a gene which is normally amplified in liposarcoma, thus reassuring us that the lipoma mass was benign.

Postoperative recovery from the lipoma excision was complicated with the formation of a seroma which was drained, and also with development of cellulitis which was managed with antibiotics. Mobility has steadily improved. Regular plastics surgery dressing clinic reviews were held until the team were happy the wound had healed well.

Figure 2 illustrates the weight change over a period of 7 years.

Investigations

MRI scan was performed preoperatively which demonstrated a large oedematous fatty swelling measuring 37 × 23 × 23 cm (figure 3). Overlying skin was thickened and there were multiple left-sided superficial inguinal lymph nodes measuring up to 15 mm. The great saphenous vein was noted to pass into the medial aspect of the swelling. Findings were consistent with an oedematous or inflamed fatty mass. However, it was not possible to exclude a diagnosis of sarcoma. A paraumbilical hernia was also noted.

Differential diagnosis

This patient had lost significant weight from diet control and also from gastric bypass surgery. However, a persistent massive left medial thigh mass remained which was of significant burden to the patient, restricting mobility and being prone to infection. With such a large mass, differential diagnoses included that of a liposarcoma, lipoma or hernia.

Hernia was excluded from MRI and for differentiation between benign and malignant swellings, pathological specimen was required. In order to differentiate between liposarcoma and lipoma, genetic testing with MDM2 was performed and found not to be amplified, thus proving the mass was that of a lipoma.

Treatment

In order to prepare for bariatric surgery, the patient was commenced on the Protein Sparing Modified Fast Diet which involves intake of high-quality protein sources from meat and fish, aiming for 1.5 g/kg for an ideal body weight protein intake per day. A carbohydrate of <20 g is taken daily and fats not found in protein sources should be avoided. It is also of importance that electrolytes are monitored including sodium, potassium, magnesium and calcium,.3

A second diet was tried, the Counter Weight Plus, which involved liquid diet for between 12 and 20 weeks, with a calorie intake of approximately 850 kcal per day.

Elective surgery was planned to excise the mass. Skin was prewashed with chlorhexidine. Anterior and posterior skin flaps were raised and the central portion of skin over the pedunculus mass was excised. A 10 kg mass was sent for pathology. The long saphenous vein was sacrificed, and several venous tributaries were identified and ligated. The wound was washed out with 4 L of saline and two 15 F drains inserted. Wound closure was obtained with 3–0 monocryl deep and 3–0 monocryl subcuticular. Supplemental 3-0 vicryl rapide was used to provide additional wound strength. The wound was finally glued and Prevena dressing applied with coverage of wool and crepe.

Outcome and follow-up

The patient was followed up in the plastic surgery clinic 2 months postsurgery and had made excellent progress. There were some small areas of wound dehiscence, the largest of which was at the distal third of the wound in a skin fold. Serous fluid continued to drain from these small areas of wound breakdown. It was agreed that he would continue being reviewed in the plastic dressing clinic until his wound has healed satisfactorily. A few weeks postoperatively, all his wounds have healed satisfactorily.