Diagnosis of fibroadenoma in breast fine needle aspirates devoid of typical stroma

Mammary mesenchymal and fibroepithelial lesions: An illustrated cytomorphologic update with differential diagnoses

The Uniform Approach to Breast Fine Needle Aspiration Biopsy was put forward by a learned group of breast physicians in 1997. This landmark manuscript focused predominantly on diagnosis and reporting of mammary epithelial lesions. Today, most American practitioners turn initially to core biopsy rather than aspiration biopsy for the first line diagnosis of solid breast lesions; however, recent efforts from the International Academy of Cytology have produced a system called the Standardized Reporting of Breast Fine Needle Aspiration Biopsy Cytology (colloquially labeled in 2017 as the "Yokohama System"), suggesting a new interest in breast fine needle aspiration (FNA), especially in resource limited settings or clinical practice settings with experienced breast cytopathologists. Fibroepithelial lesions of the breast comprise a heterogeneous group of biphasic tumors with epithelial and stromal elements. Mesenchymal lesions of the breast include a variety of neoplasms of fibroblastic, myofibroblastic, endothelial, neural, adipocytic, muscular, and osteo-cartilaginous derivations. The cytology of mesenchymal breast lesions is infrequently described in the literature and is mainly limited to case reports and small series. This illustrated review highlights the cytologic features of fibroepithelial and mesenchymal mammary proliferations and discusses differential diagnoses and histomorphologic correlates.

A Diagnostic Approach to Fibroepithelial Breast Lesions

Fibroepithelial breast lesions encompass a heterogeneous group of neoplasms that range from benign to malignant, each exhibiting differing degrees of stromal proliferation in relation to the epithelial compartment. Fibroadenomas are common benign neoplasms that may be treated conservatively. Phyllodes tumors are relatively rare lesions, and classified as benign, borderline, or malignant based on histologic evaluation of various parameters. The diagnostic interpretation of "gray-zone" fibroepithelial lesions often imposes formidable demands on a pathologist's skills. This article offers practical recommendations for the diagnostic workup of these lesions, including the appropriate utilization of ancillary investigations and the approach to core needle biopsies.

Diagnostic dilemmas and pitfalls in ThinPrep® cytology of breast fine needle aspiration biopsy:: Report of Six Cases with Histological Correlates

Fine needle aspirations (FNA) of the breast for primary diagnoses have become less popular in the USA and are usually performed for lesions with low or extremely high clinical suspicion. They are also performed for lesions in close proximity to a breast implant. Liquid-based cytological preparations, such as ThinPrep^® (TP), provide a practical alternative to clinicians who are performing FNA. Using a selection of cases that represent challenging diagnoses, we describe common diagnostic pitfalls of breast FNA that are specifically associated with this preparation. Well known breast cytology pitfalls, such as fibroadenoma, when solely examined using a TP slide can be even more challenging since the usual stripped bipolar cells seen in the background of smeared slides, can appear singly dispersed with preserved cytoplasm, resembling carcinoma. We describe that large fragments of solid papillary carcinoma are represented by mostly singly dispersed cells with plasmacytoid features that mimic those of a lobular carcinoma. Since nuclear features are more pronounced in TP, prominent nucleoli and cytological atypia can potentially be overcalled. TP processing might also lead to clumping of epithelioid histiocytes that appear atypical, which increases the suspicion of malignancy. The presence of atypical cells in a TP slide of a peri implant seroma should always undergo additional testing, especially in patients with a prior history of breast carcinoma, to determine if it represents recurrent carcinoma or an implant associated anaplastic large cell lymphoma. Familiarity with the aforementioned artifacts associated with TP is essential to avoid diagnostic misinterpretations. Diagn. Cytopathol. 2017;45:655-661. © 2017 Wiley Periodicals, Inc.