Breast Cancer Specificities of Patients With Anti-Ri Paraneoplastic Neurologic Syndromes.

Background And Objectives: Breast cancers (BCs) of patients with paraneoplastic neurologic syndromes and anti-Yo antibodies (Yo-PNS) overexpress human epidermal growth factor receptor 2 (HER2) and display genetic alterations and overexpression of the Yo-onconeural antigens. They are infiltrated by an unusual proportion of B cells. We investigated whether these features were also observed in patients with PNS and anti-Ri antibodies (Ri-PNS).

Methods: Using clinicopathologic data, DNA sequencing, and whole-transcriptome analysis, 28 BCs associated with Ri-PNS were characterized regarding oncological characteristics. Genetic alteration of the onconeural antigens and differential gene expression profiles were analyzed in the 12 available tumor samples and compared with those of 5 Yo-PNS tumors.

Results: Ri-PNS BCs were mainly luminal B invasive carcinomas that did not overexpress HER2 and were a subtype of BCs different from the ones observed in Yo-PNS BCs. They had a low expression of wild-type and deletions of 1p chromosome. Neither overexpression nor genetic alteration of the Ri onconeural antigens was found in Ri-PNS BCs. Conversely, the nature of the antitumor immune reaction in Ri-PNS BCs was similar to the one found in Yo-PNS BCs. Ri-BCs also had a high propension for early nodal regional metastasis.

Discussion: BCs associated with Ri-PNS are uncommon and the tumor subtype and their molecular and oncological characteristics are different from those of Yo-PNS and controls. Overexpression or sequence variation in the gene of the onconeural antigen is not mandatory. Conversely, Ri-PNS-associated and Yo-PNS-associated BCs display the same atypical B-cell-mediated intratumoral immune response, and tumor escape in the lymph nodes is frequent.