Answer: Tubular carcinoma

Histology: This needle biopsy shows a proliferation of tubules in and amongst benign breast tissue as well as infiltrating adipose tissue. Many of the tubules had an angulated (boat-shaped) morphology. Cytologically, these tubules lack significant atypia.

Discussion: Radial scars are characterized by a central hyalinized acellular scar with entrapped tubules which at the periphery merge in with more typical fibrocystic changes. In the current case, the stroma differs from that seen within radical scar. Furthermore, the small tubules infiltrate in and around normal breast lobules rather than merge in with florid duct hyperplasia. One would not see in the radical scar tubules infiltrating adipose tissue. Furthermore, within the tubules within a radical scar, one may often make out a two-cell layer which is lacking in the current case. Microglandular adenosis is one of the few benign entities may see tubules infiltrating adipose tissue. Microglandular adenosis, however, has a classic histology composed of rounded tubules containing dense eosinophilic secretions. In microglandular adenosis the stroma shows no reaction. These features are lacking in the current case. Sclerosing adenosis has a typical low appearance histology where the tubules have a more compressed appearance centrally opening up to more dilated tubules peripherally. In the current case there is no organization to the tubules but rather they infiltrate haphazardly throughout the stroma. The lesion, on needle biopsy, lacks any suggestion of a lobular growth pattern. A definitive diagnosis of tubular carcinoma cannot be made on needle biopsy as there may be more poorly differentiated areas that have gone unsampled. Rather, we sign these cases out as infiltrating ductal adenocarcinoma of the breast with tubular features.