This current case is a blend of the sclerosing and inflammatory variant. A collagenized background with variably dense inflammatory infiltrate characterizes this sclerotic and inflammatory variant. Image
The background is usually fibrillary, but is more sclerotic in this view. Atypical stromal cells are not easily identified.
Focally dense lymphoplasmatic inflammation predominates in some areas, obscuring the lipomatous nature of the tumor. It is important to sample thoroughly in order to exclude a dedifferentiated component.
Scattered malignant cells (bizarre stromal cells and multivacuolated lipoblasts) are present upon careful search.
Well-differentiated liposarcomas, also known as atypical lipomatous tumor, exhibit four different morphologic variants recognized by the WHO: adipocytic (lipoma-like), sclerosing, inflammatory and spindle cell. The first two variants comprise the majority of well-differentiated liposarcomas. The sclerosing variant tends to occur in the retroperitoneum and paratesticular region, whereas the lipoma-like variant is more centralized in the limbs.
Histologically, the sclerosing variant has a prominent fibrillary component containing scattered bizarre hyperchromatic stromal cells and multivacuolated atypical lipoblasts. The inflammatory variant exhibits a dense inflammatory infiltrate consisting mostly of lymphocytes and plasma cells. The inflammatory variant is also usually retroperitoneal in location and may be mistaken for an inflammatory pseudotumor.
Note that the sclerotic and inflammatoy component can obscure the lipomatous areas and thus, the specimen ought to be thoroughly sampled in order to identify the lipomatous regions as well to exclude a dedifferentiated component (Fletcher, Folpe).
Anatomic site is an important prognostic factor. The sclerosing and inflammatory variants tend to arise in the retroperitoneum, thus, excision with negative margins is more difficult than in the limbs and the recurrence is significantly higher.
→Well-differentiated liposarcomas have four recognized variants: lipoma-like, sclerosing, inflammatory and spindle cell.
→The sclerosing and inflammatory variants tend to arise in the retroperitoneum and thus, are hard to resect completely and more likely to recur.
Fletcher CDM, ed. Diagnostic Histopathology of Tumors. 3rd Ed. Philadelphia, PA: Elsevier; 2007: 1534-1539..
Folpe AL, Inwards CY. Bone and Soft Tissue Pathology: Foundations in Diagnostic Pathology Philadelphia, PA: Elsevier; 2010: 108-112.