Mass-forming papillary carcinomas in situ - Intracystic papillary carcinoma
Intracystic papillary carcinoma of the breast has provoked controversy as to whether it is truly in situ or in fact invasive disease. The issue revolves around the absence of a discernible myoepithelial layer at the interface with the adjacent stroma. Most practitioners now believe that even in the absence of invasion it is an invasive lesion but with a low potential for metastatic spread and therefore should in the first instance be managed as in situ disease. If an invasive focus is found in a subsequent excision then appropriate further treatment should be considered.
Intracystic papillary carcinoma.
Mass-forming papillary carcinomas in situ - solid papillary carcinoma
Solid papillary carcinomas of the breast are uncommon and cause considerable diagnostic difficulty, particularly on core biopsy. The key to diagnosis is the recognition of a vascular network running through the tumour - a feature that is not seen in invasive carcinomas. The tumour may be circumscribed or, less commonly, more dispersed and nodular. The presence of invasive carcinoma arising from these lesions is much more common than in intracystic papillary carcinomas.
Papillary pattern DCIS
This is uncommon. I include an example for completeness.