SPCs show solid growth patterns, while encapsulated papillary carcinoma reveals a complex expansible partially cystic mass with filiform branching papillae lined by columnar cells without neuroendocrine differentiation. SPCs also commonly show a luminal phenotype and are typically estrogen and progesterone receptor immunopositive and HER2/neu negative. This evidence concerns the gene PGR and thyroid gland papillary carcinoma.