Invasive lobular carcinoma enclosed by a benign phyllodes tumor: A case report

INTRODUCTION AND IMPORTANCE: Phyllodes tumors (PT) account for approximately 1% of all breast tumors. The coexistence of phyllodes tumor and invasive lobular carcinoma in the ipsilateral breast is extremely rare with fewer than six cases reported worldwide in the last 20 years. We hereby present the first in Taiwan. CASE PRESENTATION: A 43-year-old female was presented with a protruding tumor with bleeding tendency over left breast in 2016. Breast sonography revealed highly suspected malignancy (ACR BI-RADS category 5). Computed tomography scan disclosed a protruding mass occupying the left breast. Core needle biopsy showed a fibroepithelial lesion favoring fibroadenoma. Considering clinicopathological discrepancy, a nipple-sparing mastectomy was conducted. Pathology report revealed a benign PT with an incidental finding of invasive lobular carcinoma (pT1cN0) within the tumor. Due to tumor recurrence, the patient received re-operation of total mastectomy in 2017, and is under regular adjuvant hormonal therapy without cancer recurrence to date. CLINICAL DISCUSSION: Physicians could easily overlook carcinomas enclosed by PTs due to its occult property. However, when carcinomatous changes arise from within or along with the PT, the proposed therapeutical course may be altered. Moreover, invasive carcinoma components in PTs possess potential for lymph node metastasis. Multidisciplinary cooperation is key in detecting and managing PT with synchronous carcinomatosis. CONCLUSION: Thorough examination of the excised tumor specimen and ensuring an adequate surgical margin is necessary. Sentinel lymph node biopsy (SLNB) should be considered whenever suspicious clinical features occur in PT patients. This may aid in the detection of microscopic invasive carcinomatous change.