PMC10399263_01
Biphasic histologic features in alveolar adenoma. Hematoxylin & eosin histology examination shows a well-circumscribed (A, 10x magnification) multi-cystic lesion with ecstatic spaces (B, 50x magnification; C, 100x magnification) lined by cytological bland flat to cuboidal cells (arrow) and filled with eosinophilic granular materials (star) (D, 400x magnification). The interstitium contains cytological bland spindle cells (arrowhead) and inflammatory cells (D, 400x magnification). Immunohistochemistry staining shows (400x magnification) (E) CK7 is diffusely/strongly positive for cystic lining cells (cytoplasmic staining) and negative for stromal cells; (F) TTF1 is diffusely/strongly positive for cystic lining cells (nuclear staining) and negative for stromal cells; CD34 is diffusely/strongly positive for stromal cells and negative for cyst lining cells (G); S100 (H), smooth muscle actin (I), and Human Melanoma Black 45 (J) are negative for both cyst lining and stromal components.
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PMC10399263_01_10.1177_23247096231181959-fig1.jpg
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Microscopically, the mass was well demarcated (Figure 1(A)) and showed varying sized cystic spaces filled with eosinophilic acellular and granular materials (Figure 1(B)-(D)). No atypia, mitoses, or necrosis was identified (Figure 1(D)). The cyst lining cells were diffusely positive for cytokeratin 7 (CK7; Figure 1(E)) and thyroid transcription factor-1 (TTF-1; Figure 1(F)). The stromal cells were strongly and diffusely immunoreactive for clusters of differentiation 34 (CD34; Figure 1(G)). Immunostains for S100 (Figure 1(H)), smooth muscle actin (SMA; Figure 1(I)) and Human Melanoma Black 45 (HMB45; Figure 1(J)) were negative for the stromal cells.