In this gross specimen, a 4kg 40cm fatty tumor appears encapsulated. Pleomorphic liposarcomas are fleshy, well-circumscribed masses, most often arising in the thigh and are often quite large as seen here.

Bisecting the tumor reveals a yellow tumor with necrosis and some cystic changes. There are focally softened areas as well as indurated areas.

Pleomorphic liposarcoma is composed of a cellular pleomorphic tumor with giant and bizarre-appearing lipoblasts. These multivacuolated neoplastic cells with scalloped atypical nuclei and prominent nucleoli can be scattered or form solid areas. Nuclear pseudoinclusions and multinucleation may be seen. Thorough sampling may be necessary to find these lipoblasts.

The lipoblasts are highly vacuolated cells with markedly pleomorphic nuclei with scalloped contours. While not seen here, two-third of pleomorphic liposarcomas have a spindled and plemorphic sarcomatous appearance with fascicles of spindled atypical stromal cells. About one-third of cases have an epithelioid morphology. Rare cases appear similar to myxofibrosarcoma with a variably mxyoid background (Folpe).

A common finding are eosinophilic intracytoplasmic globules (center), but this finding is not specific and no one knows the exact nature of these droplets (Fletcher).

Plemorphic liposarcoma is a rare form of liposarcoma, accounting for 5% of all liposarcomas (Fletcher). It is an aggressive high-grade lipogenic sarcoma, virtually indistinguishable from all high grade pleomorphic sarcomas except for the presence of bizarre lipoblasts. It most often arises in the thighs of older adults. Grossly, the lesion is fleshy and areas of necrosis.

S-100 can help highlight the lipoblasts. The genetics of the tumor is highly complex, similar to most pleomorphic high grade sarcomas (Folpe).

Peak incidence in the fifth and sixth decades of life. Most frequently arises in the lower extremities, particularly the thigh. Other sites include the upper limb, trunk, retroperitoneum and less commonly, head and neck, abdomen/pelvis and spermatic cord (Hernick).

Poor; pure myxoid and atypial liposarcomas tend to recur rather than metastases. However, myxoid with round cell component, dedifferentiated and pleomorphic liposarcomas frequently have widespread metastases (Rosai).

In a study of 57 cases of plemorphic liposarcoma, follow-up data was available for 50 patients with a median follow-up time of 33 months. There was local recurrence in 34% of patients, systemic metastases in 32%, and tumor-related death in 32% (Hornick).

• Lipomatous : Liposarcoma, Well-Differentiated Type (Atypical Lipomatous Tumor)

• Lipomatous : Liposarcoma, Dedifferentiated Type

• Lipomatous : Liposarcoma, Myxoid Type

• Lipomatous : Liposarcoma, Well-Differentiated Type (Atypical Lipomatous Tumor)

• Lipomatous : Well-differentiated liposarcoma, Sclerosing Fibroinflammatory Variant