The microscopic character of secretory carcinoma in situ. a, The tumor cells were arranged in cystic and microcystic pattern, and formed a honeycomb-like appearance (HE, × 100). b, Tumor cells were mild-to-moderate atypia, with granular or vacuolated cytoplasm and vesicular nuclei containing small nucleoli (HE, × 200). c, In some areas, tumor cells were arranged in a papillary pattern within an dilated duct (HE, × 40). d, PAS-positive material in ductal lumina and in intracytoplasmic vacuoles
(PAS, × 100).