Unknown Case: Middle-aged Woman With a Large Partially Calcified Breast Mass

History

A 46-year-old woman presented with a palpable painless right breast mass. She first noticed the lump five years previously, but it rapidly increased in size over the last three months. Bilateral diagnostic mammogram (Figure 1), breast US (Figure 2), and chest CT (Figure 3) were performed.

Imaging Findings

On mammography (Figure 1), a large dense mass with indistinct margins occupying almost the entire right breast was seen. Coarse heterogeneous and popcorn-like calcifications were seen within the mass. Diagnostic US (Figure 2) showed a large irregular heterogeneous mass with indistinct margins, cystic areas, and internal vascularity on power Doppler US. Chest CT (Figure 3) did not show signs of chest wall infiltration or evidence of pulmonary metastatic disease.

Differential Diagnosis

In this case, invasive ductal carcinoma, fibroepithelial lesions, sarcoma, and lymphoma should be considered in the differential diagnosis. The absence of enlarged axillary lymph nodes slightly favors the possibility of a fibroepithelial lesion, without ruling out the possibility of primary breast sarcoma or invasive ductal carcinoma. Suspicious calcifications should raise suspicion for invasive ductal carcinoma, phyllodes tumors with or without osteosarcomatous components, metaplastic carcinoma with osteosarcomatous differentiation, and, less likely, primary or metastatic osteosarcoma.

The patient underwent US-guided core-needle biopsy of the mass, which showed increased epithelial and stromal components suggestive of a fibroepithelial lesion, with moderate stromal cellularity and scarce mitosis. Subsequently, mastectomy was performed. Pathology showed connective tissue protruding into cleft-like spaces that were covered by ductal and myoepithelial cells. Stromal cells that showed moderate atypia without a heterologous malignant element were also seen.

Diagnosis: Borderline Phyllodes Tumor

Discussion

Phyllodes tumors are uncommon fibroepithelial lesions and constitute less than 1% of all mammary tumors (1). They appear in women with a mean age of 45 years. Affected patients present with a large painless breast mass with rapid growth. Sometimes, however, patients may present with smaller masses that are indistinguishable from fibroadenomas (2). These tumors can be classified as benign, borderline, or malignant, depending on index of mitosis, tumor cellularity, tumor borders, stromal atypia, and stromal overgrowth (1,3,4).

Mammographically, these entities appear as high-density oval masses with circumscribed to indistinct margins. Although calcifications are uncommon, they could be seen in benign subtypes because of slower growth rate. Malignant subtypes with osteosarcomatous differentiation can also exhibit calcifications (3).

Sonographically, phyllodes tumors are seen as oval hypoechoic masses. Other features, such as cleft-like cystic components, hyperechoic septa, marked vascularity, and posterior acoustic enhancement, are also described (5,6)

On MRI, phyllodes tumors may present with internal hemorrhage and infarcted areas seen as T1 high signal intensity areas. Stromal hypercellularity correlates with low T2-weighted signal intensity and restricted diffusion (7)

Since phyllodes tumors present with internal heterogeneity, it is difficult to distinguish them from fibroadenoma based on core-needle biopsy samples. Furthermore, malignant subtypes can develop heterologous components that can be mistaken as sarcomas or metaplastic carcinomas with sarcomatoid differentiation. As a result, surgical excision is often advised in these cases (8)

Local recurrences are more frequent in borderline and malignant subtypes, with recurrence rates reported as high as 65% (5).

Conflict of Interest Statement

None declared.

References