Papillary Breast Carcinoma

Papillary breast carcinoma is a group of low grade, ER-positive breast cancers with a papillary architecture of fibrovascular cores covered by neoplastic epithelium. The group includes intraductal papillary carcinoma, encapsulated papillary carcinoma, solid papillary carcinoma and invasive papillary carcinoma.

Together they account for under 2% of breast cancers. Patients are mostly postmenopausal, in their 60s to 70s, and the lesion is often retroareolar.

Encapsulated and solid papillary carcinomas lack a myoepithelial layer and behave as indolent in situ like neoplasms unless a true invasive component is present.

Pathophysiology. Most are luminal A-like, ER and PR positive, HER2 negative, with low proliferation. Solid papillary carcinoma often shows neuroendocrine differentiation (synaptophysin, chromogranin) and mucin production.

Invasion. Invasion is present only when tumour cells breach the capsule or infiltrate stroma. Pure encapsulated and solid papillary carcinomas without invasion have a very low risk of nodal metastasis or distant disease.

Outcome. Prognosis is excellent. Local recurrence after excision is under 5%, and invasive papillary carcinoma behaves as low grade ductal cancer.

• Palpable retroareolar mass, or bloodstained or serous single duct nipple discharge, both common.
• Most are older women with a slowly growing painless lump, often with a cystic feel.
• Axillary nodes are rarely involved.

• Ultrasound: well defined complex cystic and solid mass, or an intracystic nodule. Mammography: well circumscribed retroareolar density. MRI: enhancing nodule within a cystic structure. Ductography is rarely needed.
• Core biopsy shows papillary fronds with fibrovascular cores. Absent myoepithelial cells (p63, calponin and smooth muscle myosin negative) around the lesion supports encapsulated or solid carcinoma. Core biopsy can understage, so complete excision is advised for any papillary lesion with atypia or a diagnosis of carcinoma.
• ER, PR and HER2 testing. Axillary ultrasound. Systemic staging only when invasive disease is large, node positive or symptomatic.

Differential diagnosis.

• Intraduct papilloma, with or without atypia
• DCIS arising in a papilloma
• Papillomatosis
• Invasive micropapillary and mucinous carcinoma
• Cystic phyllodes tumour
• Metastasis from papillary thyroid or ovarian carcinoma

Surgery. Complete excision with clear margins, which removes the lesion for pathological assessment of invasion. Mastectomy for extensive or multifocal disease.

Axilla. Sentinel node biopsy is not needed for pure encapsulated or solid papillary carcinoma without invasion. It is performed for invasive papillary carcinoma, for mastectomy, or when invasion is suspected.

Radiotherapy. Whole breast 40 Gy in 15 fractions after conservation for invasive disease or an extensive intraductal component. Radiotherapy can be omitted after discussion for small, completely excised encapsulated or solid papillary carcinoma without invasion.

Endocrine therapy for ER-positive invasive disease:

• Tamoxifen: 20 mg orally once daily for 5 years; maximum 20 mg daily; monitoring: ask about abnormal vaginal bleeding at each visit, thromboembolic symptoms, annual gynaecological review; adjustment: no renal adjustment, avoid strong CYP2D6 inhibitors (paroxetine, fluoxetine, bupropion), avoid in severe hepatic impairment and pregnancy, caution with prior venous thromboembolism.
• Anastrozole (postmenopausal women): 1 mg orally once daily for 5 years; maximum 1 mg daily; monitoring: bone mineral density at baseline then every 1 to 2 years, calcium and vitamin D, arthralgia; adjustment: none in mild to moderate renal or hepatic impairment.

Chemotherapy. Not needed for pure papillary carcinoma. Invasive disease with a ductal component is assessed by size, grade, nodes and recurrence score.

Monitoring. Annual mammography and clinical review every 6 to 12 months for 5 years.

Referral and escalation.

• Breast multidisciplinary review for any papillary lesion with atypia or carcinoma.
• Urgent assessment of new bloodstained nipple discharge.

Special groups.

• Men: rare, managed by the same principles with mastectomy more often.
• Older adults: endocrine therapy alone is sometimes used for frail patients with small ER-positive tumours.