Granular Cell Tumor Mimicking Breast Carcinoma: A Report of Two Cases

Granular cell tumor (GCT) of the breast is a rare neoplasm that can mimic the clinical and radiological features of breast carcinoma. This paper presents two case reports - a rare male case and a more common female case - to underline the diagnostic challenges posed by GCT in the breast. The male patient was initially suspected of having a breast tumor based on mammography and ultrasound findings. The female patient also exhibited radiological signs suggestive of breast cancer. In both cases, the mammograms showed irregular lesions, while ultrasounds revealed solid masses with posterior shadowing and echogenic halos, mimicking carcinoma. Dynamic contrast-enhanced magnetic resonance imaging (MRI) suggested benign patterns in both cases, but only histopathologic examination post-core needle biopsy confirmed the diagnosis of GCT. These cases highlight the variability of GCT imaging presentations and the potential for misdiagnosis as breast carcinoma. The tumors exhibited distinct histopathological features, such as large polygonal cells with granular eosinophilic cytoplasm and S100 protein, differentiating them from breast carcinoma. However, imaging alone proved insufficient for diagnosis, emphasizing the need for histopathologic confirmation. The report discusses the importance of including GCT in differential diagnoses and utilizing core needle biopsy for accurate evaluation. Both cases had no recurrence during follow-up after wide resection, indicating a favorable prognosis for GCT when properly managed.