Uncommon subtype of ductal carcinoma

Clinical History

A 66-year-old woman got a screening mammography that showed a new focal asymmetry in her left breast not present on previous mammograms. She was referred to the Breast Unit at our institution to complete work-up and undergo a core needle biopsy.

Imaging Findings

A high density spiculated mass was detected in the screening mammograms (not shown) which on ultrasound appeared as an irregular, spiculated and hypoechoic nodule of 10x9mm of size with partial posterior acoustic shadowing that was located in the lower outer quadrant (LOQ) of the left breast (Fig. 1). Surgery (Fig. 2) and sentinel lymph node biopsy were performed. The histologic examination revealed breast carcinoma composed of small glands or tubules and desmoplastic stroma with low-grade cells (Fig. 3). Immunohistochemical markers were positive for CK 19 and negative for vimentin. The value of Ki-67 was 20% (Fig. 4). The pathological stage of the breast cancer was pTNM IA (pT1cN0M0), and after surgery it was treated with radiotherapy. The patient continued follow-up every year for the past 4 years at the Breast Unit, without any signs of recurrence until the present date.

Discussion

Tubular carcinoma of the breast is an uncommon histological subtype of ductal carcinoma that is associated with an excellent prognosis. Mean age of presentation is 50 years, slightly younger than ductal carcinoma [1]. Its prevalence has been estimated to be 1.2% according to a 1997 analysis of the Surveillance, Epidemiology and End Results database. Around 65% of the patients present with a non-palpable, mammographically detected mass and it accounts for 10% of screen-detected cancers. It is the most frequent carcinoma with radial scars and can be associated with a low grade DCIS [2].

Mammography usually shows a small spiculated mass with associated microcalcifications in up to 24% of the patients; other possible radiological appearances are architectural distortion or asymmetry. Ultrasound most commonly shows hypoechoic masses with ill-defined margins and posterior acoustic shadowing [3]. The typical MRI findings include irregular, spiculated, enhancing mass. It can be T1W iso- to slightly hypointense with heterogeneous enhancement [4]. Multifocality is seen in 20% of the patients, with ipsilateral multicentric involvement in 20-50% of the cases. Hormone receptors levels are: ER(+) 80-90%, PR(+) 68-75%, and HER2(-) with a low Ki-67 (<10%) [5, 6].

Microscopically it is composed of small glands or tubules of relatively uniform calibre. There is usually a single layer of neoplastic epithelial cells arranged in tubules glands that may show irregular shapes and angular contours [2]. In the ‘pure form’ subtype the proportion of tubular structures is equal or more than 90% or mixed when 50-89% of the tubular pattern is present. The cells are low-grade, with also low mitotic rate.

This well differentiated variant shows low rates of lymph node involvement and local recurrence, and high overall survival rates when compared to standard invasive ductal carcinoma. The treatment of choice is breast-conserving surgery with clear margins, which can be adequate except for multicentric disease. Sentinel node biopsy is recommended and the use of radiation and chemotherapy is controversial, due to the low risk of local recurrence without radiation, 4% at median 5-year follow-up. Thus adjuvant therapy may not provide significant benefit, especially in the older population, although this has only been reported in one series [1, 7].

Take home message: This variant can be mammographically stable or slow-growing for years. It can even appear only as a subtle distortion, spiculated mass or be a one-view-only finding. As radiologists we should consider tomosynthesis for further evaluation in these cases.

Differential Diagnosis List

Final Diagnosis

Tubular carcinoma

URL:	https://www.eurorad.org/case/13280
DOI:	10.1594/EURORAD/CASE.13280
ISSN:	1563-4086