Table 1.

Developmental stage of spheroids and the corresponding morphological hallmarks of UDH

Stage of development of spheroid	Morphological hallmark of UDH
Freshly formed spheroid (Fig. 1A)	Mosaic-like staining pattern CK14/CK8 (16)
Two-zone spheroid (Fig. 1B)	Maturation phenotype, irregular nuclear spacing, syncytia, streaming, nuclear shape (12), mosaic-like pattern CK14/CK8
Concentric layers formed by cell cords without lumen (Figs. 2 and 3)	Concentric growth of solid-cell cords (12), mosaic-like pattern of CK14/CK8 (16)
Multilayered epithelium with lumen (Fig. 4)	Fenestrations (slit-like lumina) with peripheral epithelium and convex border with myoepithelial layer (18), apocrine tufts or snouts (9), basal myoepithelial layer, continuous lumina (19)

All: nuclear indentation (12).