Histology:
On macroscopy GCTBs are firm, solitary masses, some of them circumscribed, with a capsule, but they frequently show an infiltrative growth pattern with non-circumscribed margins [14]. They are typically homogenous with a color ranging from white to tan [14]. They can be associated with fibrosis in 40% of cases [43]. When non-encapsulated, they may infiltrate into the surrounding tissues like fibrous tissue, adipose tissue and pectoralis major muscle [14]. Due to this growth pattern, GCTBs may resemble invasive breast carcinomas [12,16]. On microscopy GCTBs show an infiltrative growth pattern in nests, cords, or sheets of large polygonal and occasionally spindled cells with abundant eosinophilic, finely granular cytoplasm and small nuclei surrounded by sclerotic stroma [14,32]. GCTs have Pustulo-ovoid bodies of Milian, which are large granules with clear halos [14,32]. The granules are strongly period acid-Schiff (PAS) positive, and they represent lysosomes. Nuclei have dense chromatin, are relatively small, and are centrally placed [1].