KIT is highly expressed in adenoid cystic carcinoma of the breast, a basal-like carcinoma associated with a favorable outcome

Abstract

Recent biological studies have classified breast carcinomas into HER2-overexpressing, estrogen receptorpositive/luminal, basal-and normal-like groups. According to this new biological classification, the objectives of our study were to assess the clinical, morphologic and immunophenotypic characteristics of adenoid cystic carcinoma of the breast in order to classify this subtype of breast carcinoma. A total of 18 cases of adenoid cystic carcinoma were identified from the Institut Curie files. Clinical information was available for 16 patients with a median follow-up of 6.5 years. Morphologically, all tumors were graded according to the system defined by Kleer and Oberman (histologic and nuclear grade). Immunophenotype was assessed with anti-ER, PR, HER-2, KIT, basal (CK5/6) and luminal cytokeratins (CK8/18) and p63 antibodies. One out of 18 tumors was nuclear grade 1 (16%), nine were nuclear grade 2 (50%) and eight were nuclear grade 3 (44%). All cases were estrogen receptor, progesterone receptor and HER-2 negative. Epithelial cells were strongly positive around glandular lumina with one or both cytokeratins, identifying the coexistence of CK5/6 þ cells, CK5/6 and CK8/18 þ cells, CK8/18 þ cells and p63 þ cells. All cases (100%) were also KIT positive. In all, 15 patients were treated by surgery. Nine of them received adjuvant radiotherapy. Follow-up was available for 16 patients. In all, 14 patients were alive. Two of them, initially treated by surgery only, presented a local recurrence. Two patients died (one of them treated by radiation therapy only died from her disease). Our study shows that adenoid cystic carcinoma of the breast is a special, estrogen receptor, progesterone receptor, HER-2 negative and highly KIT-positive, basal-like breast carcinoma, associated with an excellent prognosis. This highly specific immunophenotype could be useful to differentiate adenoid cystic carcinoma of the breast from other subtypes of breast carcinoma such as cribriform carcinoma.

Secretory breast carcinomas with ETV6-NTRK3 fusion gene belong to the basal-like carcinoma spectrum

“…11 Although most triplenegative tumors with a basal-like immunophenotype are presumed to be high-grade tumors (medullary carcinoma, 16 metaplastic carcinoma 17 and invasive ductal carcinoma, a small subset of invasive cancers of special types such as adenoid cystic carcinomas have also been shown to present a basal-like immunophenotype. 3,18 Assessment of a basal-like immunophenotype in clinical practice further demonstrated that the basal-like spectrum of tumors encompasses various histologic types of tumors associated with different prognoses. The present immunoprofile results show that secretory breast carcinomas are triple-negative and express basal markers.…”

Basal-like and triple-negative breast cancers: a critical review with an emphasis on the implications for pathologists and oncologists

“…18,21,32 The similarity of these features with those of human papilloma virus-induced squamous cell carcinoma of the head and neck has led to the identification of the role of retinoblastoma gene (RB1) in these tumors. 33 However, not all basal-like cancers are of the IDC-NST type; the majority of medullary and atypical medullary, 4,34-36 metaplastic, 4,37,38 secretory, 39 myoepithelial, and adenoid cystic carcinomas 4,40 of the breast also show a basal-like phenotype. 5 More recently, a subgroup of lobular carcinomas has been shown to express high-molecular-weight cytokeratins, 41 however it remains to be determined whether these cases truly show a basal-like transcriptome.…”

“…After the 8-year mark, the hazard rate for patients with grade 2 or ERpositive cancers is actually higher than that of patients with basal-like cancers. Finally, some tumors in the 'basal' group have a favorable prognosis, eg, adenoid cystic carcinomas 40,121 and secretory carcinomas. 39 This emphasizes that basal phenotype and bad behavior are not inextricably linked and serves to highlight the heterogeneous nature of basal-like carcinomas.…”

HER2 status of bone marrow micrometastasis and their corresponding primary tumours in a pilot study of 27 cases: a possible tool for anti-HER2 therapy management?

“…Cytokeratins 8/18 expression was also assessed on these 20 out of 27 primary tumours according to a previously published protocol (Azoulay et al, 2005).…”