Postneoadjuvant Pure and Predominantly Pure Intralymphatic Breast Carcinoma: Case Series and Literature Review

Locally advanced breast cancer is typically treated with neoadjuvant chemotherapy to decrease tumor size and optimize surgical results. Cases of pathologic complete response, are associated with favorable long-term outcomes. The American Joint Committee on Cancer (AJCC) defines pathologic complete response as a lack of residual invasive disease in the breast or lymph nodes or only residual ductal carcinoma in situ. Three studies have examined the unique pattern of postneoadjuvant pure or predominantly pure intralymphatic carcinoma. These studies are small and the prognosis associated with this disease pattern is still unclear. The current study aims to describe clinicopathologic findings associated with pure and predominantly pure intralymphatic carcinoma postneoadjuvant chemotherapy. Electronic medical records were searched to identify patients treated with postneoadjuvant mastectomy between 2010 and 2017. Cases were included if they met the previously defined definitions for pure or predominantly pure intralymphatic carcinoma. Of 479 postneoadjuvant mastectomies, 5 patients had pure intralymphatic carcinoma and 6 patients had predominantly pure. Overall, 50% (3/6) of patients with predominantly pure pattern died of metastatic disease within 14 months of mastectomy, whereas 1 patient with pure intralymphatic carcinoma (ypN0) died of metastatic disease 25 months postmastectomy, revealing a better prognosis associated with pure intralymphatic carcinoma when compared with predominantly pure. The diligent gross examination is required to identify patients with both patterns of residual disease. A standardized approach to incorporating lymphovascular invasion into postneoadjuvant staging may be useful from both a clinical and research perspective. The published case numbers remain small and understanding the true clinical significance still depends on additional studies.