Findings: The mammogram shows a 3 x 2.5 cm lobulated, circumscribed mass in the right breast. The breasts are otherwise mostly fat replaced. To ensure that the radiographic finding corresponded to the palpable abnormality, a metallic BB was placed in the region of palpable abnormality. An ultrasound performed in conjunction with the mammogram demonstrates a complex cystic mass. A mostly anechoic structure is present but there is a focal area of wall thickening with a mural projection.

Diagnosis: An excisional biopsy revealed intracystic papillary carcinoma with focal invasion into the fibrous capsule of the surrounding cyst wall, forming a mass 2.0 cm in greatest dimension.

Discussion: In an elderly patient even a well-circumscribed mass should be viewed with suspicion, especially if it is palpable. The ultrasound findings of a complex mass also raise concern. The differential diagnosis of a complex cyst is cyst with debris/hemorrhage, papillary lesion (benign and malignant), necrotic cancers and mucinous/colloid carcinomas.

Intracystic papillary carcinomas when small are not evident mammographically. They do not produce the fibrotic proliferation associated with other forms of ductal carcinoma. As the intracystic carcinomas enlarge, they tend to form fairly well-circumscribed masses.

Pathologically intracystic papillary carcinoma is an unusual variant of ductal carcinoma in situ. In the past it had been used to describe a heterogenous group of sharply demarcated cyst-like carcinomas. In current practice it should be reserved for ductal carcinoma in situ, usually of the papillary type, that involves a grossly visible dilated duct. They can vary in size from 1.0 to 14 cm. The inner wall of the dilated duct/cyst may be smooth or granular. It is frequently tan or brown - reflecting recent hemorrhage. Tumor cells are found along the cyst lining or float free in the fluid.

References:
Kopans DB. Breast Imaging. J. B. Lippincott, 1989.

Fechner RE, Mills SE. Breast Pathology Benign Proliferations,
Atypias and In Situ Carcinomas. ASCP Press 1990.

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