Abstract
To determine non-radiographic risk factors differentiating atypical lipomatous tumors (ALTs) from lipomas. All patients with deep-seated lipomatous tumors of the extremities treated from January 2000 to October 2010 were retrospectively reviewed. Factors reviewed included age, gender, tumor location, size, histology, local recurrence, dedifferentiation, and metastasis. Multivariate logistic regression models were used to evaluate the effects of patient characteristics on ALT status. Ninety-four lipomas and 46 ALTs were included. Patients with an ALT were older (median: 60.5 vs. 55 years). Lipomas were evenly distributed between upper (48.9%) and lower extremities (51.1%), whereas ALTs predominately involved the lower extremities (91.3%). Median ALT size (22 cm) was greater than lipomas (10 cm), p < 0.0001. One lipoma (1.04%) recurred at 77 months and five ALTs (10.9%) recurred at an average of 39 months (19-64 months). Two ALTs originally treated with wide resection recurred with a dedifferentiated component and were treated with wide re-excision and chemotherapy. No metastases or tumor-related deaths occurred in either group at the time of last follow-up. Patients older than 60 years, tumors greater than 10 cm, or thigh location, were more likely to be diagnosed with an ALT (p < 0.05). Lipomatous tumors were more likely to be ALTs when the tumor was at least 10 cm in size, located in the thigh, or found in patients that were 60 years of age or older. These risk factors may be used to guide management and surveillance strategies, when lipomatous tumors do not display characteristic radiographic features.
Highlights
Lipomatous tumors of the extremities are the most common soft tissue tumors encountered in clinical practice with the majority of these tumors being lipomas and atypical lipomatous tumors (ALTs) [1,2,3]
The orthopedic oncology database was queried to identify all patients with a histopathologic diagnosis of lipoma or ALT of the extremities treated at our institution from January 1, 2000 to October 1, 2010
Twenty-six patients were excluded; 10 ALTs and 4 lipomas had undergone previous excision, 6 tumors were diagnosed as lipomas but the initial histopathologic diagnosis could not exclude ALT nor could the independent blinded review, 1 ALT had myxoid features, 2 tumors had a final histopathologic diagnosis of fibrolipoma, 2 were diagnosed as hibernoma, and 1 lipoma had a hemagioma within the lesion
Summary
Lipomatous tumors of the extremities are the most common soft tissue tumors encountered in clinical practice with the majority of these tumors being lipomas and atypical lipomatous tumors (ALTs) [1,2,3]. Differentiating ALTs from Lipomas liposarcoma (8%) [4]. Atypical lipomatous tumor (ALT) is synonymous with well-differentiated liposarcoma [5], which is a low grade tumor that is usually deep-seated and located in the buttock, thigh, and retroperitoneal areas. ALTs can be locally aggressive [6,7,8] but have very low potential to metastasize or dedifferentiate [5]. They are composed of variable amounts of mature adipose tissue interspersed with enlarged atypical adipocytic and stromal cells with hyperchromatic nuclei and prominent, thickened fibrous bands. Lipomas on the other hand are benign tumors composed of mature fat that present as solitary, slow-growing, and painless masses in the subcutaneous tissue; they may be deep to the fascia or intramuscular
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