Figure 2:

Low-grade serous tumors with histologic transformation to TP53-mutated high-grade carcinoma components. (A,B) Case 26, composed of low-grade serous carcinoma (left) and high-grade serous carcinoma (right), separated by dashed line (A, 200X magnification). LG - low-grade; HG - high-grade. Immunohistochemical analysis of p53 shows a wildtype (wt) expression pattern in the low-grade area and aberrant (abn) cytoplasmic expression in the high-grade area (B, 200X magnification). (C) Case 14, with the higher-grade component showing moderate (Gr. 2) nuclear atypia, but aberrant diffuse p53 expression (inset), consistent with a high-grade carcinoma (400X magnification). (D-F) Case 18, with high-grade carcinoma (delineated by dashed lines) emerging from a background of low-grade serous carcinoma (D, 200X magnification). Immunohistochemical stain for p53 shows a subclonal aberrant pattern, with foci of overexpression, corresponding with the morphologically more atypical areas (E, 100X magnification). Higher magnification of high-grade focus, with marked nuclear atypia. Representative “large” (red arrowheads) and “small” nuclei (blue arrowheads) demonstrate >3:1 nuclear size variation (F, 400X magnification). (G-I) Case 24. Immunohistochemical staining for p53 reveals a heterogeneous subclonal aberrant expression pattern. (G, 40X magnification). Morphologically, there are areas of low-grade and high-grade tumor, separated by dashed line (H, 200X magnification). These areas correspond to wildtype and aberrant diffuse p53 expression patterns, respectively (I, 200X magnification).