Figure 2. Histological findings of uterine dedifferentiated MLA. (A) Low-power magnification showed destructive myometrial invasion of MLA. (B) In contrast to MLA (left half), UC (right half) showed no glandular differentiation or organized pattern. (C) The transition (purple arrows) from MLA (left upper corner) to UC was readily identifiable. (D-F) MLA showed predominantly small tubular and glandular growth architecture. The tubules consisted of a single layer of cuboidal cells that were closely packed, with no intervening stroma, forming a back-to-back or cribriform appearance. Intraluminal eosinophilic colloid-like materials (E; blue arrows) were frequently identified. In several foci, comedonecrosis-like pattern (F), showing central necrosis filling the dilated glandular lumina and partially surrounded by tumor glands, was noted. (G) Examination of MLA under high-power magnification demonstrated glandular crowding and focal cribriform architecture. The tumor cell nuclei displayed mild-to-moderate pleomorphism. (H) UC consisted exclusively of sheets of discohesive, variable-sized pleomorphic cells possessing abundant eosinophilic cytoplasm, large vesicular nuclei, and prominent, deeply eosinophilic nucleoli. Mitotic figures (green arrows) were frequently observed. (I-J) In some areas of the UC component, severe nuclear pleomorphism and multinucleated giant cells (J; yellow arrows) were noted. Staining method: A–J, hematoxylin and eosin staining. Original magnification: A–B, 20×; C, 40×; D–E, 100×; F, 80×; G–J, 400×.