PMC9750768_01
Cut surface of the ovary shows three cystic lesions which are well-demarcated from the remaining ovarian parenchyma (asterisk). The largest locule has nodular white lining with focal hemorrhage, whereas the other two locules show smooth internal surface.
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fig1
The cut surface showed three abutting cystic lesions, which were well-demarcated from the remaining rim of ovarian parenchyma (Figure 1).
Microcystic stromal tumor (MST) of the ovary. (a) Solid nodule with infiltrative border, separate from a mucinous cyst (asterisk) by thick fibrous stroma (H&E, 1.25x). The cyst is lined with benign mucinous epithelium (inset) (H&E, 20x). (b) The irregular infiltrative-like border of MST (H&E, 10x). (c) Solid pattern with microcysts of variable caliber and the diffuse presence of bizarre cells. Large spaces containing blood and fibrin are also observed (H&E, 10x). (d) Bizarre cells with epithelioid features and pleomorphic hyperchromatic nuclei (H&E, 40x). (e) Aggregates of signet ring-like cells (H&E, 40x). (f) Typical MST features of cellular areas with hyalinized fibrous bands (H&E, 10x). Monotonous tumor cells with bland nuclei punctuated by relatively uniform microcystic spaces (inset) (H&E, 40x).
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fig2
These components were separated by ovarian stroma without mixed or transitional area (Figure 2(a)). This component had an irregular border characterized by an infiltrative-like interface with surrounding fibrous ovarian stroma (Figure 2(b)). Tumor cells were arranged in predominant solid pattern with occasional microcystic spaces of variable caliber (Figure 2(c)). Bizarre cells with enlarged hyperchromatic nuclei or multinucleation were diffusely distributed and were present in approximately 80% of tumor areas (Figure 2(d)). Cells with intracytoplasmic vacuoles (signet ring-like) were also mingled with these bizarre cells (Figure 2(e)). MST were focally observed, characterized by microcystic architecture with hyalinized fibrous stroma (Figure 2(f)) and uniform bland, round-to-oval tumor nuclei with fine chromatin and pale to eosinophilic cytoplasm (Figure 2(f), inset). Mitotic figures were not detected. The two cystic locules with smooth internal surface were lined by benign mucinous epithelium (Figure 2(a), inset).
Immunohistochemical stains of MST. (a) Diffuse, strong nuclear and cytoplasmic expression of beta-catenin (20x). (b) Diffuse, strong cytoplasmic positivity for CD10 (20x). (c) Patchy positivity for WT-1 (20x). (d) EMA negativity in MST (arrow). Note the positive staining in mucinous cystadenoma (lower) (1.25x).
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Immunohistochemically, tumor cells in the largest locule showed diffusely strong nuclear and cytoplasmic reactivity for beta-catenin (Figure 3(a)), diffuse positivity for CD10, patchy positivity for WT-1 (Figures 3(b) and 3(c)), and focal expression of CK (AE1/AE3), whereas the immunostains for inhibin, calretinin, AFP, CK7, and EMA were negative (Figure 3(d)). The mucinous component was positive for CK, CK7, and EMA (Figure 3(d), arrow) and showed normal membranous staining for beta-catenin.