PMC8592773_01
Scan shows a pedunculated neoplasm confined to the dermis that is composed of mixed areas of hypercellularity and hypocellularity. The stroma varies with predominantly myxoid areas and other foci that are more collagenous.
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fig1
Histopathological examination features an exophytic, pedunculated intradermal neoplasm abutting the epidermis extending through the papillary and reticular dermis (Figure 1) without involvement of the subcutis. Rare mitotic figures are identified (<1/10 HPFs), necrosis is absent, and no pleomorphic lipoblasts are identified.
(a) Low power demonstrates a neoplasm abutting the epidermis composed of a hypocellular myxoid area overlying a more cellular area containing numerous univacuolar lipoblasts (H&E, 40x). (b) Sheets of spindle-shaped pleomorphic cells with enlarged hyperchromatic nuclei beneath the epidermis (H&E, 400x).
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fig2
There is variable cellularity (Figure 2) composed of multiple cell types, including adipocytes with marked variation in size, spindle cells exhibiting nuclear atypia ranging from mild to severe (Figures 2(b), 3, and 4(a)), a few multivacuolated lipoblasts (Figure 3), focally abundant univacuolar lipoblasts (Figure 3(b)), and atypical multinucleated cells.
(a) Multivacuolated lipoblast surrounded by lipocytes that vary markedly in size and shape (H&E, 400x). (b) Area where univacuolar lipoblasts with scalloped nuclei predominate amid spindle cells with ovoid nuclei and the presence of ropey collagen (H&E, 400x). (c) Multinucleated giant cells with hints of ropey collagen (H&E, 400x). (d) Strikingly "bizarre" pleomorphic cell (H&E, 400x).
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fig3
There is variable cellularity (Figure 2) composed of multiple cell types, including adipocytes with marked variation in size, spindle cells exhibiting nuclear atypia ranging from mild to severe (Figures 2(b), 3, and 4(a)), a few multivacuolated lipoblasts (Figure 3), focally abundant univacuolar lipoblasts (Figure 3(b)), and atypical multinucleated cells. Multinucleated giant cells are identified (Figure 3(c)) as well as areas of "ropey" collagen (Figure 4(b)). The intercellular matrix is variable and includes both myxoid and collagenous areas. "Bizarre" pleomorphic cells are readily identified (Figure 3(d)).
(a) Confluence of pleomorphic cells within the papillary dermis (H&E, 400x). (b) Thickened ropey collagen with myxoid stroma, pleomorphic cells, and variable lipoblasts (H&E, 400x).
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fig4
Multinucleated giant cells are identified (Figure 3(c)) as well as areas of "ropey" collagen (Figure 4(b)).
(a) S100 demonstrates prominent staining of univacuolar lipoblasts (100x). (b) Immunohistochemistry for Rb demonstrates absence of reactivity for Rb in the majority of tumor cells.
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fig5
The neoplastic cells fail to display reactivity with immunostains for AE1-AE3, CD34, Desmin, MDM2, and CDK4, but in some small foci, labelling with S100, particularly among univacuolar lipoblasts, stain is present (Figure 5). There is significant loss of Rb expression (Figure 5(b)).