The differential diagnosis of a pelvic soft tissue mass containing mainly fat includes lipoma, atypical lipoma
, one of the lipoma variants or well-differentiated liposarcoma.
(6.) Skipworth RJ, Smith GH, Stewart KJ, Anderson DN: The tip of the iceberg: a giant pelvic atypical lipoma
presenting as a sciatic hernia.
, atypical intramuscular and well differentiated retroperitoneal liposarcoma: A reappraisal of 30 cases formerly classified as well differentiated liposarcoma.
The lesion was resected under the presumed diagnosis of low-grade liposarcoma or atypical lipoma
. On gross dissection the mass was homogeneous yellow adipose tissue with small fibrous septations.
Histologically, they can be classified as simple lipoma, fibrolipoma, spindle cell lipoma, intramuscular or infiltrating lipoma, angiolipoma, pleomorphic lipoma, myxoid lipoma, and atypical lipoma
. Intramuscular or infiltrating lipoma is an uncommon mesenchymal tumor, usually appearing in the extremities or trunk but rarely occurring in the oral cavity .
The differential diagnosis of similar uterine tumors with adipose tissue and spindle cells include spindle cell lipoma, angiolipoma, angiomyolipoma, leiomyoma with fatty degeneration, atypical lipoma
, and well-differentiated liposarcoma.
He term atypical lipoma
was first introduced in 1974  to describe lobulated, well-circumscribed, large lesions that are histologically characterized by mature adipocytes of varying size and scattered atypical stromal cells with hyperchromatic nuclei (Figure 1) [2, 3].
The radiological differential diagnosis of both benign and malignant fat containing tumours, including atypical lipoma
, haemangioma, angiolipoma, and liposarcoma, therefore warrants histological characterisation prior to excision.
Helms, "Lipomas, lipoma variants, and well-differentiated liposarcomas (atypical lipomas
): results of MRI evaluations of 126 consecutive fatty masses," American Journal of Roentgenology (AJR), vol.
Helms, "Lipomas, lipoma variants and well-differentiated liposarcomas (atypical lipomas
): results of MRI evaluations of 126 consecutive fatty masses," American Journal of Roentgenology, vol.
Although CT and MRI may help to differentiate between atypical lipomas
, myxoid liposarcomas, pleomorphic round-cell liposarcomas, and dedifferentiated liposarcomas, histologic examination remains the diagnostic gold standard and aids in preoperative planning.
Rydholm, "Deep-seated ordinary and atypical lipomas
: histopathology, cytogenetics, clinical features, and outcome in 215 tumours of the extremity and trunk wall," Journal of Bone and Joint Surgery B, vol.