Is the CPC a mass party? Yes.

Credit to /u/mughal_emperor on reddit:

Sources:

• CPC members exceed 90 million
• Long term survey reveals Chinese government satisfaction

The Communist Party of People's Republic of China have 93 million members who are mostly proletariat with 1/3rd of them being Farmers, Fishers and Herders which enabled people from lower strata to voice their problem.

CPC members by their occupation

If we assume that each member of the party have a husband/wife and at least one child then it sums up to 279 million (93*3) which is roughly 1 in every 5 citizens of PRC (279/1394 = 0.2). If we add their parent, grandparent, cousin etc.. the number will much higher.

Hence one can say that CPC is very people and people are CPC. Add to the fact that CPC have some 99% approval rate among the proletariat which undoubtedly makes PRC a Proletariat state.