Triple-negative breast cancers (TNBC), as a group of tumours, have a worse prognosis than stage-matched non-TNBC and lack the benefits of routinely available targeted therapy. However, TNBC is a heterogeneous group of neoplasms, which includes some special type carcinomas with a relatively indolent course. This review on behalf of the European Working Group for Breast Screening Pathology reviews the literature on the special histological types of BC that are reported to have a triple negative phenotype and indolent behaviour. These include adenoid cystic carcinoma of classical type, low-grade adenosquamous carcinoma, fibromatosis-like metaplastic carcinoma, low-grade mucoepidermoid carcinoma, secretory carcinoma, acinic cell carcinoma, and tall cell carcinoma with reversed polarity. The pathological and known molecular features as well as clinical data including treatment and prognosis of these special TNBC subtypes are summarised and it is concluded that many patients with these rare TNBC pure subtypes are unlikely to benefit from systemic chemotherapy. A consensus statement of the working group relating to the multidisciplinary approach and treatment of these rare tumour types concludes the review.

Percutaneous core biopsy (CB) has been introduced to increase the ability of accurately diagnosing breast malignancies without the need of resorting to surgery. Compared to conventional automated 14 gauge needle core biopsy (NCB), vacuum-assisted needle core biopsy (VANCB) allows obtaining larger specimens and has recognized advantages particularly when the radiological pattern is represented by microcalcifications. Regardless of technical improvements, a small percentage of percutaneous CBs performed to detect breast lesions are still classified, according to European and UK guidelines, in the borderline B3 category, including a group of heterogeneous lesions with uncertain malignant potential. We aimed to assess the prevalence and positive predictive values (PPV) on surgical excision (SE) of B3 category (overall and by sub-categories) in a large series of non-palpable breast lesions assessed through VANCB, also comparison with published data on CB. Overall, 26,165 consecutive stereotactic VANCB were identified in 22 Italian centres: 3107 (11.9%) were classified as B3, of which 1644 (54.2%) proceeded to SE to establish a definitive histological diagnosis of breast pathology. Due to a high proportion of microcalcifications as main radiological pattern, the overall PPV was 21.2% (range 10.6%-27.3% for different B3 subtypes), somewhat lower than the average value (24.5%) from published studies (range 9.9%-35.1%). Our study, to date the largest series of B3 with definitive histological assessment on SE, suggests that B3 lesions should be referred for SE even if VANCB is more accurate than NCB in the diagnostic process of non-palpable, sonographically invisible breast lesions.

The purpose of this study was to evaluate the reliability of image-guided 14-gauge needle core biopsy in the diagnosis of radial scar without associated atypical epithelial proliferation, by comparison with definitive histological diagnosis on surgical excision. The records of 8792 consecutive image-guided 14-gauge needle core biopsy of the breast performed from January 1996 to December 2009 were reviewed. Forty-nine cases of radial scar without associated atypical epithelial proliferation were identified and compared with definitive histological diagnosis on surgical excision. The definitive histological diagnosis on surgical excision confirmed the results of image-guided 14-gauge needle core biopsy in 36 of 49 cases (73.5%), in 9 cases (18.3%) radial scar was associated with atypical epithelial proliferation, while 4 cases out of 49 cases were upgraded to carcinoma (3 cases of ductal carcinoma in situ and one case of invasive lobular carcinoma), with an underestimation rate of 8.2%. A diagnosis of radial scar without associated atypical epithelial proliferation on image-guided 14-gauge needle core biopsy does not exclude a malignancy on surgical excision; consequently during the multidisciplinary discussion further assessment by surgical excision or vacuum-assisted excision, as recently reported, needs to be considered to obtain a definitive histological diagnosis.