RB1 and parathyroid gland adenoma: Furthermore, the addition of other biomarkers including Bcl-2a, parafibromin, Rb, and p27 may play an important role in identifying atypical parathyroid adenomas which do not present with all the classic histologic features (unequivocal angioinvasion, perineural, and gross local invasion) that we associate with parathyroid carcinoma [40].