TBX1 and Histiocytosis: However, it is important to consider interosseous lipoma as a potential differential diagnosis during histopathological examination. Immunohistochemical studies are useful in ruling out other differential diagnoses, including metastasis from renal cell carcinoma (positive for epithelial markers like cytokeratins AE1/AE3), histiocytosis (positive for histiocytic markers such as CD68 and CD163), and chordoma (positive for brachyury).