Synchronous bilateral phyllodes tumors with discordant grades and false-positive axillary 18F-FDG PET-CT uptake: a case report and literature review

Rationale Phyllodes tumors are uncommon fibroepithelial breast neoplasms with variable biologic behavior. Synchronous bilateral phyllodes tumors are exceptionally rare, and the interpretation of 18 F-fluorodeoxyglucose positron emission tomography/computed tomography ( 18 F-FDG PET-CT) may be confounded by tumor necrosis and inflammation, leading to false-positive nodal staging. Patient concerns A 44-year-old Korean woman presented with a rapidly enlarging, painful, ulcerated left breast mass for 3 months. She had no nipple discharge, fever, or weight loss. A right breast lesion was clinically occult. Diagnoses Ultrasound showed a right breast hypoechoic nodule (BI-RADS 4A) with scant vascularity and an elastography score of 2, and a giant heterogeneous hypervascular left breast mass with enlarged axillary lymph nodes and an elastography score of 4. 18 F-FDG PET-CT revealed intense uptake in the left breast mass (SUV max 11.5) and markedly FDG-avid ipsilateral axillary nodes (SUV max 9.0), suspicious for metastasis; mild uptake was seen in the right breast nodule (SUV max 1.7) without definite distant metastasis. Core needle biopsy supported a fibroepithelial neoplasm favoring phyllodes tumor. Final pathology confirmed a left borderline phyllodes tumor and a right benign phyllodes tumor; all 21 axillary lymph nodes showed reactive hyperplasia with sinus histiocytosis and no metastasis. Interventions After multidisciplinary review, the patient underwent excision of the right breast mass with frozen-section margin assessment, left total mastectomy including the nipple-areola complex and ulcerated skin to achieve negative margins, and level I-II axillary lymph node dissection because sentinel lymph node biopsy was considered unreliable in the setting of massive ulceration and severe axillary edema. Outcomes Recovery was uneventful. Ceftriaxone sodium 2.0 g was given intravenously once daily from 1 day before surgery through postoperative day 5. No wound infection, seroma, fever, or unexpected adverse events occurred. At 1 month, CA125, CA15-3, and CA19–9 had normalized. Lessons In phyllodes tumors, marked axillary FDG avidity may reflect reactive inflammation rather than true nodal metastasis, particularly in giant ulcerated tumors with necrosis. Management should emphasize complete excision with negative margins and cautious axillary surgery guided by clinicopathologic correlation.