Breast metastases from extramammary malignancies: typical and atypical ultrasound features

Abstract

Breast metastases from extramammary malignancies are uncommon. The most common sources are lymphomas/leukemias and melanomas. Some of the less common sources include carcinomas of the lung, ovary, and stomach, and infrequently, carcinoid tumors, hypernephromas, carcinomas of the liver, tonsil, pleura, pancreas, cervix, perineum, endometrium and bladder. Breast metastases from extramammary malignancies have both hematogenous and lymphatic routes. According to their routes, there are common radiological features of metastatic diseases of the breast, but the features are not specific for metastases. Typical ultrasound (US) features of hematogenous metastases include single or multiple, round to oval shaped, well-circumscribed hypoechoic masses without spiculations, calcifications, or architectural distortion; these masses are commonly located superficially in subcutaneous tissue or immediately adjacent to the breast parenchyma that is relatively rich in blood supply. Typical US features of lymphatic breast metastases include diffusely and heterogeneously increased echogenicities in subcutaneous fat and glandular tissue and a thick trabecular pattern with secondary skin thickening, lymphedema, and lymph node enlargement. However, lesions show variable US features in some cases, and differentiation of these lesions from primary breast cancer or from benign lesions is difficult. In this review, we demonstrate various US appearances of breast metastases from extramammary malignancies as typical and atypical features, based on the results of US and other imaging studies performed at our institution. Awareness of the typical and atypical imaging features of these lesions may be helpful to diagnose metastatic lesions of the breast.

Keywords: Breast; Extramammary; Metastasis; Ultrasound.

Fig. 1

55-year-old woman with metastatic pancreatic head cancer. A, B. Breast ultrasound images show well circumscribed, oval-shape hypoechoic masses in superficial area of right breast (A) and in middle of left breast (B), suggesting metastasis. C, D. Contrast enhanced abdomen CT scan shows ill-defined low density mass in pancreatic head (arrow in C) with multiple liver metastases (D).

Fig. 2

47-year-old woman with metastatic diffuse large B cell lymphoma. A, B. US of right mid outer breast (A) and lower outer breast (B) show multiple circumscribed hypoechoic masses of metastatic lymphoma confirmed by US-guided core needle biopsy. US = ultrasound

Fig. 3

44-year-old woman with metastatic signet ring cell carcinoma from stomach. A, B. Craniocaudal and mediolateral oblique mammograms show skin thickening (arrows), coarse trabecular pattern and thickening of Cooper's ligaments (arrowheads) in right breast. C. Ultrasound of right breast shows diffuse parenchymal heterogeneity with skin thickening and lymphatic dilatation. D. Barium study of stomach reveals large ulceroinfiltrative mass (arrows and arrowheads) from upper body to prepyloric antrum.

Fig. 4

34-year-old man with metastatic NK/T cell lymphoma. A. US shows diffuse hyperechoic infiltrations with thickening of skin and subcutaneous fat tissue and dilated lymphatic channels. B. PET-CT shows increased FDG uptake in corresponding area. US-guided core needle biopsy of right lower outer breast area revealed NK/T cell lymphoma. US = ultrasound

Fig. 5

58-year-old woman with metastatic adenocarcinoma from lung. A. Mediolateral oblique mammogram shows palpable irregular mass (arrow below skin marking) and two round masses in upper outer quadrant of left breast (arrows) with enlarged lymph nodes in axilla (arrowheads). B, C. US of left upper outer breast shows irregular mass with marked hypoechogenicity, microlobulated margins, and peritumoral infiltration, similar to those of invasive ductal carcinoma (B), and smaller masses with similar features in peripheral side of main mass (C). D. US of left axilla reveals several enlarged lymph nodes with ill-defined margins, and obliteration of normal fatty hilum, suggesting metastasis. E. Chest CT scan shows irregular spiculated mass in left lower lobe, suggesting lung cancer. US = ultrasound

Fig. 6

59-year-old woman with metastatic rectal cancer. A. Transverse US image of left axillary tail area shows heterogeneous hyperechoic mass-like lesion with ill-defined margins (arrows). B. Ray-sum image reformed from CT colonography reveals abnormal wall thickening and infiltration (arrows) involving distal rectum, suggesting rectal cancer.

Fig. 7

41-year-old woman with metastatic hepatocelluar carcinoma. A. Craniocaudal mammogram shows lobular mass with relatively circumscribed margins (arrows). B. Ultrasound of left upper outer breast shows large, solid mass with microlobulated margin and internal tubular anechoic areas (arrowheads). C. Abdomen CT scan reveals hepatic mass with contrast enhancement in arterial phase, suggesting hapatocelluar carcinoma (arrow).

Fig. 8

53-year-old woman with metastatic insular carcinoma of thyroid gland. A. Mediolateral oblique mammogram shows focal asymmetry in left upper outer breast (arrows). B. US of left upper outer breast shows circumscribed benign-looking mass with multifocal cystic changes, mimicking resolving hematoma in middle of breast parenchyma. C. Contrast enhanced neck CT scan reveals large heterogeneous low density mass in left thyroid gland (arrow). D. Follow-up US after 4 months shows markedly enlarged hypoechoic mass with circumscribed margins and multiple small internal cystic portions (arrows). US = ultrasound

Fig. 9

58-year-woman with multiple myeloma. A. Mediolateral mammogram shows relatively well-circumscribed hyperdense mass. B. US of right upper center breast shows heterogeneous hypoehoic mass with microlobulated margins and bulging contour to subcutaneous layer. C. Color Doppler US shows increased vascularity within tumor. US = ultrasound

Fig. 10

13-year-old girl with acute myeloid leukemia. A. US of left upper outer breast shows large, well-circumscribed oval shape mass with marked hypoechogenicity with nodular hyperechoic portion. This feature mimics intracystic solid mass. B. On color Doppler US, marked hypoechoic area was revealed to be solid tumor with increased vascularity. C. Very hypoechoic area was high cellular area of chloroma as revealed by core needle biopsy specimen (hematoxylin & eosin staining, × 400) (B). US = ultrasound

Fig. 11

40-year-old woman with metastatic lung cancer. A. US of left breast shows multiple hypoechoic masses with segmental distribution from nipple and dilated segmental ducts with irregular wall thickening, mimicking DCIS or intraductal papillary lesions. B. US of left axilla shows enlarged lymph nodes, mimicking metastasis from breast cancer. C. Chest CT scan revealed multiple masses and consolidations in left upper lobe with large amount of pleural effusion caused by pleural seeding. Biopsy from breast masses revealed metastatic adenocarcinoma from lung which was positive for TTF-1 and negative for BRST-2. US = ultrasound, DCIS = ductal carcinoma in situ, TTF = thyroid transcription factor-1, BSRT = Gross Cystic Disease, Fluid Protein-15 (GCDFP-15)