Review of metaplastic carcinoma of the breast: imaging findings and pathologic features

Abstract

Metaplastic carcinoma (MPC), an uncommon but often aggressive breast cancer, can be challenging to differentiate from other types of breast cancer and even benign lesions based on the imaging appearance. It has a variable pathology classification system. These types of tumors are generally rapidly growing palpable masses. MPCs on imaging can present with imaging features similar to invasive ductal carcinoma and probably even benign lesions. The purpose of this article is to review MPC of the breast including the pathology subtypes, imaging features, and imaging pathology correlations. By understanding the clinical picture, pathology, and overlap in imaging characteristics of MPC with invasive ductal carcinoma and probably benign lesions can assist in diagnosing these difficult malignancies.

Keywords: Metaplastic carcinoma; invasive ductal carcinoma; spindle cell.

Figure 1

A 58-year-old female with palpable mass in the right breast diagnosed as spindle cell type metaplastic carcinoma: (a) Photomicrograph (H and E, high-power magnification) shows a moderately cellular spindle lesion with elongated spindle cells, bland cytologic features, and squamous cell nest (red arrow)indicating differentiation. (b) Photomicrograph (immunoperoxidase AE1/AE3).

Figure 2

A 64-year-old patient with palpable left breast mass diagnosed as squamous cell type metaplastic carcinoma: Photomicrograph (H and E, high-power magnification) shows large pleomorphic cells (short arrow) with squamous differentiation and keratin pearls (long arrow).

Figure 3

A 51-year-old female with palpable mass in the left breast with pathology of metaplastic carcinoma, with osseous metaplasia. Photomicrograph (H and E, low-power magnification) shows spindle cells with osteoid formation (arrow).

Figure 4

Mammographic appearance of metaplastic carcinoma in two patients, both having metaplastic carcinoma mixed with invasive carcinoma. (a) A 49-year-old female called back from screening mammogram shows a circumscribed mass with partially defined (thin arrow) and partially spiculated (thick arrows) border on spot compression craniocaudal mammogram view of her right breast. (b) A 51-year-old female called back from screening shows a circumscribed mass with partially spiculated border (thin arrows) with adjacent circumscribed satellite mass (thick arrow) on spot compression mediolateral oblique mammogram view.

Figure 5

A 64-year-old female presented with a palpable mass in her left breast. (a) mediolateral oblique mammogram view and (b) craniocaudal mammogram view show an irregular mass (long arrows) with pleomorphic calcifications (short arrows). Final histopathologic diagnosis was metaplastic carcinoma, squamous subtype.

Figure 6

Ultrasound images of three patients with metaplastic carcinoma, all show posterior acoustic enhancement. (a) A 49–year-old female with a palpable mass in her right breast. Transverse gray-scale imaging shows an irregular hypoechoic mass with posterior acoustic enhancement (arrows). (b) A 49-year-old female called back from screening for a mass in her right breast. Transverse gray-scale imaging demonstrates a hypoechoic mass with irregular margins (long arrows) and posterior acoustic enhancement (short arrows). (c) A 52-year-old female who presented with a palpable mass in her right breast. Ultrasound gray-scale imaging shows a large mass with partially circumscribed margins (long arrows) in her area of palpable concern and posterior acoustic enhancement (short arrows).

Figure 7

A 40-year-old patient who presented with palpable left breast: Ultrasound image shows hypoechoic microlobulated mass with parallel orientation (wider than tall) (arrows) which can be seen with probably benign features. This lesion was biopsied due to the palpable presentation and microlobulated borders and pathology diagnosis showed metaplastic carcinoma.

Figure 8

A 57-year-old female with a palpable mass in her right breast: Sagittal and transverse gray-scale ultrasound images show a solid hypoechoic mass with internal cystic component (thin arrow), partially defined and partially irregular margins, and posterior acoustic enhancement (think short arrows). Pathology showed metaplastic carcinoma, spindle type with osseous metaplasia.

Figure 9

A 49-year-old female with newly diagnosed metaplastic carcinoma, matrix-producing subtype mixed with invasive ductal carcinoma in her right breast: (a) Axial T2-weighted MR image shows a hyperintense mass (arrow), (b) Axial T1-weighted MR image shows the mass is hypointense (arrow), (c) Axial T1-weighted fat suppressed subtracted post-contrast MR imaging shows the mass is heterogeneously enhancing mass with irregular margin (arrow).

Figure 10

A 57-year-old female with newly diagnosed metaplastic carcinoma, spindle cell subtype with osseous metaplasia in her right breast: (a) Axial fat suppressed T2-weighted MRI MRI shows hyperintense region with central cystic necrosis (arrow), (b) Axial T1-weighted MRI shows hypotense regions, and (c) T1-weighted fat suppressed subtracted post-contrast image shows heterogeneously enhancing regions with irregular margins and central cystic necrosis.

Figure 11

A 47-year-old female who presented with a palpable lump in her left breast (a) Mediolateral oblique mammogram shows an irregular large mass in the left upper breast (arrow). (b) Transverse gray-scale image shows an irregular hypoechoic mass (double lined arrows) with internal anechoic cystic components (thin arrows) and posterior acoustic enhancement (short thick arrows). (c) Sagittal fat suppressed subtracted post-contrast T1-weighted MR image shows irregular peripheral rim enhancing large mass in the left breast. (d) Photomicrograph (H and E, high-power magnification) shows abnormal cells with increased cytoplasm, cells undergoing mitosis (arrows), and larger pleomorphic cells (short thick arrow). Final histopathologic diagnosis was metaplastic carcinoma, squamous subtype which often correlates with metaplastic carcinoma containing more cystic components.