Endocrine-responsive breast cancer special types: who cares?

So, who actually cares about endocrine-responsive special types? At least the expert panel of the St Gallen consensus does [1]. Their recommendations for systemic treatment made in March 2011 were based on six subtypes; five from a simplified version of the intrinsic biological classification [2] and the sixth combining 'special histological types'. This last group represents up to 25% of all breast cancers [3] and can be subdivided into an endocrine-responsive group and an endocrine-non-responsive group. The publication from the European Institute of Oncology (EIO) of Milan published in this issue of the journal concentrates on a large series of endocrine-responsive tumours [4]. This publication has many strengths. It presents a large series of 1665 special-type cancers, out of 7372 invasive ductal luminal breast cancers accrued in a single institution, over a short period of time (9 years), and with 5.8 years of follow-up. All cases were re-evaluated independently by two of the pathologists and the criteria used to define the special types are provided in the publication. A detailed description of systemic adjuvant treatment is provided. Based on these strengths, this publication brings important data on the associations between special types and prognosis. The EIO series confirms the excellent prognosis of two special types, the tubular and cribriform types, accounting for 4.5% of all luminal breast cancers (333/7372), with a 5-year disease-free survival for the pooled analysis of these two groups of 98.7% compared with 87.4% for invasive ductal carcinoma (IDC). This group (n = 83) confirms the excellent prognosis of tubular carcinoma previously reported, e.g. in a recently published series of 102 tubular carcinomas from a single institution (the Nottingham series) with long follow-up [5]. In this series, none of the patients with a tubular carcinoma developed distant metastasis. The only discordant series that reported no differences between tubular carcinoma and grade 1 IDC was from a cancer registry database without central pathology review [6]. Regarding the cribriform group in the EIO series (n = 250), 22 tumours were T2, 48 presented with nodal involvement and 6 were HER2 positive. Interestingly, the authors divided this special type according to two immunohistochemically defined tumour subtypes, luminal A and B. Although 24% (59/250) of cribriform carcinomas were classified as luminal B cancers, their prognosis remained excellent (Figure 1, panel luminal B). This excellent prognosis remains in the multivariate analysis with hazard ratios (HRs) of 0.48, 0.35 and 0.57 for disease-free, …