The authors present a case of a neuroendocrine carcinoma in an asymptomatic 75-year-old woman, detected in routine breast screening. The lesion was visible at mammography as a well circumscribed, medium density nodule, with no associated microcalcifications, and at ultrasonography as a hypoechoic nodule, with irregular shape and ill-defined margins. Magnetic resonance imaging revealed findings consistent with malignancy.

Keywords: Carcinoma; Neuroendocrine; Breast; Imaging.

OBJECTIVE: To review the imaging features of granular cell tumors of the breast (on mammography, ultrasound, and magnetic resonance imaging), establishing a pathological correlation, in order to familiarize radiologists with this entity and make them aware of the differential diagnoses, other than malignancy, of lesions with spiculated margins. MATERIALS AND METHODS: We reviewed the medical records (from a clinical-pathology database and picture archiving and communication system) of five patients with a pathologically confirmed diagnosis of granular cell tumor of the breast, treated at the Portuguese Oncology Institute of Lisbon, in the city of Lisbon, Portugal, between January 2012 and December 2018. RESULTS: All five tumors exhibited imaging features highly suggestive of malignancy (BI-RADS 5 lesions), namely spiculated margins, significant depth, and posterior acoustic shadowing (on ultrasound). One tumor showed a kinetic curve indicative of washout on magnetic resonance imaging, two were adherent to the pectoralis muscle, and one was accompanied by skin retraction. Pathology provided the definitive diagnosis in all cases. CONCLUSION: Granular cell tumors of the breast pose a diagnostic challenge because they can present with clinical and imaging features mimicking malignancy, and the diagnosis is therefore provided by pathology. Radiologists should be familiarized with this entity, so they can be aware of the fact that breast lesions with spiculated margins can be indicative of diagnoses other than malignancy.

Keywords: Granular cell tumor; Breast neoplasms; Schwann cells.