Invasive Lobular Carcinoma Mimicking Papillary Carcinoma: A Report of Three Cases

Abstract

Encapsulated and solid papillary carcinomas (EPCs and SPCs) are considered historically as a special form of ductal carcinoma in situ. Invasive lobular carcinoma (ILC) is characterised by a discohesive growth pattern. There are several variants of ILC, but, as yet, no papillary subtype has been identified. Here we report 3 cases of ILC presenting as papillary carcinoma (PC) with a typical solid papillary growth pattern. One case was reported on core biopsy as EPC (B5a). The 3 ensuing resection specimens showed features typical of SPC with a circumscribed malignant epithelial proliferation containing fibrovascular cores and surrounded, at least focally, by a thick fibrous capsule. The lobular nature of these tumours was confirmed on the resection specimens by the absence of E-cadherin and β-catenin membrane expression. The invasive nature was confirmed by the presence of entrapped fat cells, the absence of myoepithelial cells and focal merging of the solid papillary areas with classic ILC at the periphery. Of note, 1 case was a recurrent carcinoma without an in situ component. Conclusion: This study provides further evidence that EPC and SPC represent a unique growth pattern of breast carcinomas rather than reflecting the in situ or invasive nature of the tumour, and that ILC can acquire a papillary growth pattern.

Subclonal analysis in a lobular breast cancer with classical and solid growth pattern mimicking a solid‐papillary carcinoma

“…However, the use of this term is not without controversy . Rakha et al have considered but rejected complete overgrowth of an intraductal papilloma by LIN as a possible explanation for this unusual growth pattern in the mammary gland . With regard to our case, we concur with Rakha's view because of the complete absence of a myoepithelial cell layer, which is usually retained in a papilloma with overgrowth by LIN.…”

“…Recently, Rakha et al have described a new ILBC variant which mimics a solid-papillary growth pattern and resembles EPBC [19]. The present work confirms this recently described ILBC variant with solidpapillary-like growth pattern and provides further evidence that it evolves from classical ILBC by subclonal evolution.…”

“…Both cases featured a main tumour with a fibrous capsule or pseudocapsule and a peculiar form of altered solid growth mimicking a solid‐papillary‐like growth pattern. Rakha et al , pointed out that the well‐defined margin, the capsule, intratumoural cystic areas, and supporting fibrovascular cores distinguish this growth pattern from the solid variant of ILBC as described by Fechner et al . In the present case, enhanced tumour vascularisation was also noted clinically on pre‐operative Doppler ultrasound and CNB sampling was associated with significant bleeding.…”

“…The present work confirms this recently described ILBC variant with solidpapillary-like growth pattern and provides further evidence that it evolves from classical ILBC by subclonal evolution. The first of the three cases described by Rakha et al and the mammary carcinoma characterized here have several features in common [19]. Both cases were initially considered as EPBC on CNB.…”

“…The first of the three cases described by Rakha et al and the mammary carcinoma characterized here have several features in common . Both cases were initially considered as EPBC on CNB.…”