Several IHC markers, including p27, CyclinD1, RB1, BCL2, MDM2, p53, galectin 3, and PGP 9.5, have been studied in parathyroid tumors; however, their use in routine clinical diagnostics is yet to be validated.11,12 The Ki67 labeling index of more than 5% has been associated with malignant behavior.13 In our case, the Ki67 labeling index was overall low, with only a few hotspots showing ~5% positivity. Here, RB1 is linked to tumor of parathyroid gland.