For this case I have not any doubt this is a solid papillary carcinoma.

SPC defined by Maluf sndf Koerner (Solid papillary ca of the breast: a form of intraductal carcinom with endocrine differentiation frequently associated with mucinous carcinoma. Am J Surg Pathol. 1995;19:1237-1244). : These tumors had the characteristic appearance showing nodular proliferations of neoplastic cells in which each nodue appeared to represent a distendeed well-cricumscribed duct with a thickened fibrous wall. Broad bands of dense fibrotic stroma with no or little intervening breast tissue separated individual nodule.  The cellular proliferation solid in architecture but supported in all cases by hyalinized fibrovascular cores. Often it is a diagnosis in  low power. We can appreciate some fibrovascular cores in fig 1, 3, 4. above case. Myoepithelial cells in periphery can be present or absent in SPC.

DCIS with solid growth pattern and PSC are not the same terminology.  PSC has its charateristic appearance as mentioned above.

Lack of myoepithelial cells around the periphery of the neoplastic nodules in some cases raise the possibility that some of SPCs may represent circumscribed nests of invasive ca rather than variant of DCIS.

In this case myoepthelial cell in the periphery are present. So it is just a variant of DCIS. Clinical prognosis  is similar to DCIS.

Abin: I will appreciate if you can translate this part into Chinese. Thanks, cqzhao

abin译：

本例我毫无疑问地认为它是SPC。
1995年Maluf等提出SPC(Solid papillary ca of the breast: a form of intraductal carcinom with endocrine differentiation frequently associated with mucinous carcinoma. Am J Surg Pathol. 1995;19:1237-1244)。SPC特征性的表现为：肿瘤细胞结节状增生，每个结节呈界清的扩张导管结构，围绕厚的纤维壁。致密的纤维性间质，呈宽束状，其中有少量或无乳腺组织穿插，这些乳腺组织由单个结节分隔的。在所有病例，这些富于细胞的增生呈实性结构，但有透明变性的纤维血管轴心支持。这种特征通常以低倍镜下即可诊断。我们可以在图1、3、4中辨认一些纤维血管轴心。SPC中结节周围的肌上皮细胞可以存在也可能缺失。
实性生长型DCIS和SPC不是同义词。SPC有自己特征性的表现，如上所述。
部分病例中，肿瘤结节周围缺乏肌上皮细胞，这一现象提出一种可能性：部分SPC可能是界清的浸润性癌巢，而不是DCIS的亚型。
本例，结节周围存在肌上皮细胞。因此这例只是DCIS的一种变型。临床预后与DCIS相似。

（abin附：晚上要飞到青岛去，我得在离开前完成任务，呵呵。谢谢Dr.Zhao详细讲解）