Granular cell tumor presenting as subcutaneous nodule mimicking local recurrent breast cancer: A diagnosis by fine needle aspiration cytology

Abstract

Granular cell tumor (GCT) is rare and shows neuroectodermal differentiation. GCT in most cases arises from the tongue and dermis. Herein, we report a case of GCT diagnosed by fine needle aspiration cytology (FNAC). A woman in her 50s underwent left total mastectomy and rectus abdominis myocutaneous flap owing to left breast cancer. Ten years later, ultrasonography of the reconstructed breast showed a low-echoic mass of 12 mm diameter, and FNAC was performed. In the FNAC specimens, there were numerous granular materials in the background, and ovoid to polygonal atypical cells appeared singly or in clusters. The atypical cells showed a low N/C ratio, bland nuclei, small nucleoli, and cytoplasm with abundant eosinophilic granules. The cytodiagnosis of GCT was carried out. Core needle biopsy of the mass showed atypical cells with the same morphology as the atypical cells seen in the FNAC specimens, which formed nests with a syncytial appearance. Immunohistochemistry demonstrated that the atypical cells were positive for S100, calretinin, and inhibin, consistent with GCT. In the present case, FNAC plays an important role in the diagnosis of GCT.