A Study On Epidemiology Of Subcutaneous Lipomas
Lipoma is a slow growing, encapsulated, lobulated, fluctuant and painless tumour composed of fat cells. They occur anywhere in the body where fat is found and hence the name ‘universal tumour’ or ‘ubiquitous tumour’. Head and neck, abdominal wall and thighs are the favoured sites. The masses are often benign, and while the age of onset can vary, they most often develop between the age of 40 and 60. All 126 patients who had a non-visceral lipoma diagnosed on histopathological examination during a period of 1 year were analysed retrospectively as regards the age, gender, size, site and multiplicity of the lipomas. 71. 90% (75 out of 126) were smaller than 5 cm. Multiple subcutaneous lipomas were found in 22 patients (17. 46%), most of them young males. 62. 98 % (70 out of 126) patients were between the age group of 40 to 60 years. Males were more commonly affected as 78 (61. 90%) patients were males and 48 (38. 09%) patients were females.
Introduction
Lipomas present as the most common tumour in the body. More common in obese individuals1, these benign soft tissue neoplasms typically develop in the 5th to 7th decade of life. Lipomas are rarely found in children. Histologically, lipomas are nearly indistinguishable from normal adipose tissue. Although the histological appearance resembles mature adipose tissue, lipomas are not derived from mature adipocytes but rather from mesenchymal preadipocytes. Lipomas are estimated to be multiple in 5-15% of patients. Multiple causative factors have been proposed that include genetic, traumatic, and metabolic triggers. Lipoma formation following physical trauma has been reported widely. Growth factors, cytokines, and other inflammatory mediators released following blunt trauma to soft tissue induce pre-adipocyte differentiation into mature adipocytes and formed a clinically apparent mass. Fat necrosis and the extravasation of blood secondary to trauma stimulated preadipocyte differentiation has also been postulated.
Materials and Methods
This was a retrospective study where patient data was collected from the Surgical Outpatient department records at the department of Surgery in a peripheral hospital in Nasik, of all patients who reported with a subcutaneous, painless, slow growing tumour who were clinically diagnosed as lipoma. Further histopathology reports of these patients who underwent excision of the tumour were studied and data analysed.
Inclusion and exclusion criteria
All asymptomatic, subcutaneous swellings were included in the study. FNAC was done for all patients prior to excision of the tumour and FNAC proven lipoma patients were included in the study. Spinal cord lipomas diagnosed on MRI scan imaging and lipoma of the breast diagnosed on Ultrasonography studies and FNAC were excluded. No FNAC report was suggestive of malignancy.
Sample collection
Sample was personally sent by the operating / treating Surgeon in the Operating room under sterile conditions after excision of the tumour and was transported to the lab within one hour of collection.
Statistical analysis
All 126 patients who had a non-visceral lipoma diagnosed on histopathological examination during a period of 1 year were analysed retrospectively as regards the age, gender, size, site and multiplicity of the lipomas.
Results
98 % (70 out of 126) patients were between the age group of 40 to 60 years. Males were more commonly affected as 78 (90%) patients were males and 48 (09%) patients were females. 78 out of 126 lipomas were found on head and neck and trunk making it. 52%. (15%) out of 126 lipomas affected the forearm. . 90% (75 out of 126) were smaller than 5 cm. Multiple subcutaneous lipomas were found in 22 patients (. 46%), most of them young males.
Discussion
Lipomas occur anywhere in the body where fat is found and hence the name ‘universal tumour’ or ‘ubiquitous tumour’. Lipomas are defined as mesenchymal tumors which typically lie subcutaneously. Less commonly, they can also be found on internal organs, such as stomach and bowels. These masses are not typically attached to underlying muscle fascia. Lipomas are composed of lobulated, slow-growing, mature adipose tissue, having a minimal connective tissue stroma. They are commonly enclosed in a thin, fibrous capsule.
Pathophysiology
Multiple causative factors have been proposed that include genetic, traumatic, and metabolic triggers. Lipoma formation following physical trauma has been reported widely. Lipomas have been associated with numerous pathophysiological processes. Diabetes, hyperlipidemia, mitochondrial dysfunction, and endocrinopathies such as nodular goiter, multiple endocrine neoplasia type, and Cushing's syndrome have been noted.
Presentation
Patients often complain of a soft, mobile mass of tissue they can feel under the skin. These are typically painless unless they encroach joints, nerves, or blood vessels. Rarely, these lipomas can form in muscles or organs. Lipomas are mostly harmless and are only excised if they cause pain due to their location, if they are impacting an organ’s function or for cosmetic reasons.
Histology
Histologic examination of lipomas reveals mature, normal-appearing adipocytes with a small eccentric nucleus. Histologic subtypes of lipomas include angiolipomas, myelolipomas, angiomyolipomas, myelolipomas, fibrolipomas, ossifying lipoma, hibernomas, spindle cell lipomas, pleomorphic lipomas, chondroid lipomas, and neural fibrolipomas. Common lipomas and its variants must be distinguished from liposarcomas which are a malignant lipomatous neoplasm containing lipoblasts, which are characterized by coarse vacuoles and one or more scalloped, hyperchromatic nuclei.
Diagnosis
When subcutaneous, diagnosis can be made by a characteristic “doughy” feel on palpation. Application of an ice pack to the tumor to chill and harden the fat has also been used to aid in diagnosis. On plain radiograph, lipomas appear as an area of characteristic radiolucency referred to as a “water-clear density. Ultrasound examination demonstrates a homogeneous and circumscribed hyperechoic area. Both CT and MR imaging are reliable for localization, diagnosis, size estimation, as well as evaluation of bony involvement.
Treatment
The treatment modalities include intra-lesional steroids16, intralesional transcutaneous sodium deoxycholate17 injections, liposuction18 of the tumor, or surgical excision. Surgical excision is likely the most effective method to prevent recurrences, though the encapsulation must also be removed for the most effective treatment and to decrease the risk of reoccurrence. If the decision is made to excise lipomas, then it should be done while the lesions are smaller rather than after they grow larger to reduce the risk of these encroaching on joints, nerves, and blood vessels, thus making the excision more difficult and invasive. However, surgical resection or observation without intervention remain the standard of care.
Complications
Lipomas rarely cause complications. However, patients with untreated compression syndromes may experience decreased neurological function and intractable neuropathic pain. Rarely, recurrence may occur and is typically associated with incomplete excision of deep, infiltrative lesions or lesions entangled within neurovascular structures.
Malignant variation
Liposarcomas present as one of the most common soft tissue sarcomas of the body. Like lipomas, these tumors usually present as a small, slowly enlarging painless mass, although high-grade lesions may develop rapidly. Liposarcomas most commonly present as deep-seated tumors in the retroperitoneum or, classically, on the thighs. The etiology of a liposarcoma is unknown, but most are thought to arise de novo. Reports of malignant transformation of lipomas are rare in the literature. Treatment of liposarcomas requires wide local excision and in some cases may necessitate amputation. Occasionally, (neo)adjuvant chemotherapy or radiotherapy are administered, especially for high-grade lesions. The most common complications of liposarcomas are recurrence and metastasis.
Conclusion
Lipomas are common, benign, slow growing, generally asymptomatic tumour. Simple subcutaneous lipomas may be diagnosed by history and physical examination alone. FNAC may be done to differentiate them from epidermoid cyst or ganglion which are the closest differential diagnoses. Most lipomas are treated with surgical excision with few complications or recurrence. Malignant degeneration is rare. The prognosis for benign lipomas is very good. Once these tumors are excised, mainly for cosmetic reasons, they often do not return. However, is imperative that the fibrous capsule surrounding the lipoma is entirely removed to prevent recurrence.
