The General Surgeon's Quandary: Atypical Lipomatous Tumor vs Lipoma, Who Needs a Surgical Oncologist?

Abstract

Background Differentiating large lipomas from atypical lipomatous tumors (ALT) is challenging and preoperative management guidelines are not well-defined. The diagnostic ambiguity leads many surgeons to refer all patients with large lipomatous masses to an oncologic specialist, perhaps unneccessarily. Study Design In this retrospective cohort study of patients with nonretroperitoneal lipomatous tumors, preoperative characteristics discernible without invasive diagnostic procedures were evaluated for diagnostic predictive value. Results 319 patients (256 with lipomas, 63 with ALTs) treated between 1994 and 2012 were identified. Patients with ALTs were older (60.5 vs. 53.5 years, p<0.0001), had larger tumors (16.0 vs 8.3 cm, p<0.0001), had tumors more often located on an extremity (88.9% vs. 60.5% torso, p<0.0001), and more frequently had a history of prior operations at the same site, exclusive of excision leading to diagnosis and referral (20.6% vs. 5.9%, p=0.001). Local recurrence was observed in 2 patients with lipomas (0.8%) vs. 14 with ALTs (22.6%, p<0.0001). No patients with ALTs developed distant metastases or disease-specific mortality with a median follow-up of 27.4 months (range 0–164.6 months). On multivariate analysis age ≥55 years, tumor size ≥10 cm, extremity location, and history of prior operations were predictors for diagnosis of ALT (p<0.05). Conclusions Characteristics of lipomatous masses that are associated with a diagnosis of ALT include patient age ≥55 years, tumor size ≥10 cm, previous resection, and extremity location (vs torso). These easily identifiable traits may guide surgical management or referral to a specialist.

Low Recurrence Rate and Risk of Distant Metastases following Marginal Surgery of Intramuscular Lipoma and Atypical Lipomatous Tumors of the Extremities and Trunk Wall

“…Studies concerning ALT recurrence rates are more often reported in the literature, and as with IML these studies have also shown great variance, ranging from 7.5-22.6% [8][9][10][11][12]. Only a few of these studies calculate a proper LRFS (89-95%) after 5 years [11,12], and only 1 study also calculated a 10-year LRFS of 82% [11], which is in good agreement with our ALT findings.…”

UK guidelines for the management of soft tissue sarcomas

“…Differentiating lipoma and ALT radiologically is not reliable but certain features seen on MRI can be helpful such as size and intratumoural septation [138, 139]. Histological and cytogenetic analysis of tumour allows confirmation of diagnosis, although small pre-operative biopsies may be misleading [140, 141].…”

Diagnostic performance of MRI and histology in assessment of deep lipomatous tumours

“…Despite their often large size, marginal excision of ALTs outside the capsule of the tumour results in low local recurrence rates of approximately 10 per cent, usually many years after primary surgery. The rate of dedifferentiation is very low and there are almost no reports of metastatic spread or disease‐specific mortality. As a result, the surgery performed for both deep lipomas and ALT is often identical and only rarely involves radical resection.…”

“…Lipomatous tumours have a spectrum of biological behaviour, from benign lipomas, to well differentiated liposarcomas/atypical lipomatous tumours (ALTs), to high‐grade liposarcomas. Well differentiated liposarcomas/ALTs of the trunk and extremities are reported to rarely dedifferentiate (2 per cent) and no disease‐specific mortality has been described, unlike retroperitoneal liposarcomas which have a high rate of dedifferentiation and worse outcomes. Consequently, the WHO now recommends that these tumours are described as ALT in the trunk and extremities, and well differentiated liposarcoma in the retroperitoneum.…”