MUC1 and granular cell tumor: Histologically, pituicytomas consist of bipolar spindle cells in fascicles; granular cell tumors show polygonal cells with PAS-positive, diastase-resistant cytoplasmic granules; spindle cell oncocytomas display oncocytic change and abundant mitochondria; and ependymal pituicytomas exhibit perivascular pseudorosettes and EMA positivity in apical or dot-like patterns.