Disclosed herein is a crystalline Form C of 1-((R)-3-(4-amino-3-(4-phenoxyphenyl)-1H-pyrazolo[3, 4-d]pyrimidin-1-yl)piperidin-1-yl)prop-2-en-1-one, wherein the crystalline form has an X-ray powder diffraction (XRPD) pattern comprising 2-Theta peaks at about 7.0? about 14.0? about 15.7? about 18.2? about 19.1? about 19.5? about 20.3? about 22.1? and about 22.9? Also disclosed is a crystalline Form C of 1-((R)-3-(4-amino-3-(4-phenoxyphenyl)-1H-pyrazolo[3, 4-d]pyrimidin-1-yl)piperidin-1-yl)prop-2-en-1-one, wherein the crystalline form has a differential scanning calorimetry (DSC) thermogram having an endotherm having an onset at about 134 癈 to about 135 癈 with a peak at about 137 癈 to about 139 癈. Further disclosed are pharmaceutical formulations and medical uses of crystalline Form C.