A 45-year-old male patient, morbidly obese, presented a soft-tissue tumor in the right thigh, which had been growing in size during the previous six months. No surgical history. Clinical examination revealed a large pedunculated mass, mobile, soft, and painless, associated to trophic changes in the surrounding skin.
MRI showed a soft-tissue mass, pedunculated, which involved the skin and subcutaneous tissue without compromising the fascia or the adjacent muscle planes, formed by an adipose matrix with inflammatory changes, with some septums of fibrous aspect. The dermis looked thickened and edematous. After administration of intravenous paramagnetic contrast, lesion enhancement was observed, probably related to its inflammatory component.
Background: Massive localized lymphedema, or pseudosarcoma, is an uncommon benign pathology, mainly affecting morbidly obese patients with an age range of 25 to 70 years. Its etiology has not been fully elucidated; however, this process is probably related to an obstruction located at the level of the lymphatic drainage, or due to different factors involved. The risk factors for the development of this pathology are: overweight, sedentarianism, history of axillary or inguinal lymphadenectomy, history of severe trauma, significant weight loss after bariatric surgery, post-surgical of hernioplasty or scrotum, and endocrinological alterations such as hypothyroidism.
Clinical perspective: It is characterized by a large pedunculated mass, accompanied by trophic changes in the surrounding skin, acquiring a “peau d’orange” aspect [1], located mainly in the thigh, although it can also be present, less commonly, in the scrotum, inguinal region, abdomen, popliteous hole, and at suprapubic level.
Due to the dimensions this mass may acquire, added to the physical contexture characteristic of these patients, radiological evaluation of this pathology is difficult, especially with magnetic resonance imaging because of the size of the coils, tumor location, resonator tube diameter and different possible artifacts.
Imaging Perspective: Massive localized lymphedema, also called pseudotumor, due to its macroscopic characteristics and size, could simulate a liposarcoma. However, the presence of vascular tissue at the level of the union of adipose and connective tissue, as well as the absence of cellular atypia and invasion of adjacent muscle tissue would rule out diagnosis of the latter [4].
The surgical treatment was chosen with a very good evolution in the coming months.
The final diagnosis anatomopathological report, revealed a proliferation of mature adipocytes, delimited by dense fibroconnective tracts, richly vascularized, together with the presence of an infiltrate of monoclonal cells and fibroblasts associated to alterations in the surrounding skin, in which different degrees of parenchymatous atrophy coexist with fibrosclerosis.
Outcome: Since there is a direct correlation between the disease and morbid obesity, a conservative treatment is applied, consisting in hygienic-dietary measures such as weight reduction, compression of the affected zone, manual lymphatic drainage and correct skin hygiene, which would complement the surgical treatment, regarded as treatment choice. This behavior reduces morbidity and prevents future infections, besides providing the accurate diagnosis [1, 2, 3].
Massive Localized Lymphedema or Pseudosarcoma
Based on the provided MRI images and the patient’s medical history, a large pedunculated soft tissue mass with relatively well-defined boundaries is observed in the subcutaneous tissue of the right thigh. It is primarily characterized by fatty signal components and distinct fibrous septa. Localized peau d’orange changes can be seen in the surrounding skin. Due to the sizeable mass, there is also some degree of nutritional disturbance in the overlying skin.
MRI sequences indicate that the lesion mainly consists of adipose tissue, with fibrous septa of variable thickness and visible vascular structures. No definite signs of infiltration into muscle tissue are evident. Although the overall margins appear relatively clear, further detailed imaging may be limited by the patient’s body habitus and the large size of the mass.
All of the above diagnoses require confirmation through histopathological examination and immunohistochemistry.
Considering the patient’s middle age and severe obesity (prone to lymphatic drainage obstruction), the pedunculated, slowly enlarging mass, MRI findings predominantly showing adipose tissue with fibrous proliferation, and pathological results confirming a lesion composed of proliferating mature adipocytes with abundant fibrous septa—after ruling out malignant entities like liposarcoma—the most likely diagnosis is:
Massive Localized Lymphedema (MLL), also referred to as “Pseudosarcoma.”
Since this condition is associated with severe obesity, a comprehensive management strategy is recommended, integrating both surgical and conservative approaches:
For lesions that are very large, symptomatic, or significantly impact the patient’s quality of life, surgical excision can be considered. Postoperative lymphatic drainage and the use of compression garments help reduce recurrence and improve quality of life.
Based on the patient’s degree of obesity and lower limb condition, it is advisable to gradually increase physical activity after a thorough professional assessment. The FITT-VP principle may be followed:
Particular attention should be paid to lower limb weight-bearing capacity and fluctuations in blood pressure and heart rate to prevent falls, joint injuries, or excessive cardiorespiratory strain during exercise.
Disclaimer: This report is provided as a reference based on the available information and does not replace in-person consultation or professional medical advice. The patient should seek further evaluation and treatment under the direction of a specialist.
Massive Localized Lymphedema or Pseudosarcoma
