CCND3 and splenic diffuse red pulp small B-cell lymphoma: CCND3 mutations have been identified in 20–24% cases of SDRPL and almost invariably comprise missense variants in the negative regulatory proline, glutamic acid, serine, and threonine (PEST) domain, involving the amino acids T283, P284, and I290 which are part of a phosphorylation motif that regulates cyclin D3 phosphorylation and stability [64,140].