An uncommon rapid growing breast tumour: phyllodes tumour

Clinical History

A 61-year-old woman came for follow-up of a left sided breast tumour. One year earlier biopsy of the lesion showed findings suggestive for a sclerosed fibroadenoma. However tissue sample was rather small, ultrasound was non-specific and MRI findings (from another hospital) suspicious for malignancy. For this reason the gynaecologist asked a follow-up MRI.

Imaging Findings

On inversion recovery T2-weighted imaging (WI) the mass was hyperintense with hypointense areas and hypointense septa. The maximum diameter was 3.5 cm. (Eleven months earlier the lesion was composed of multiple small nodular masses with total diameter of 2 cm) On dynamic contrast enhanced T1-WI the mass showed a marked inhomogeneous enhancement (Fig. 1). Kinetic curves displayed a quick intensity rise with wash-out. Because of these malignant characteristics we categorised the mass BI-RADS 4c. A new diagnostic mammography and ultrasound were performed. Mammography showed a lobulated well-circumscribed nodule with heterogeneous density medial in the left breast (Fig. 2). A septated heterogeneous mass was seen on sonography with solid and cystic components (Fig. 3). Solid components were vascularised as seen on colour Doppler imaging. Core biopsies were compatible with benign phyllodes tumour. The tumour was surgically removed and histopathology showed a borderline phyllodes tumour (Fig. 4).

Discussion

Phyllodes tumour represents less than 1% of all breast tumours. The peak incidence is between 35 and 55 years. The tumour has characteristic leaf-like stromal projections in cystic cavities. The malignancy grade is categorised as benign, borderline or malignant based on tumour margins, stromal cellularity and overgrowth, stromal cell atypia and mitotic activity.
Patients typically present with a painless rapid growing breast mass for which imaging is requested.
Mammography shows a non-specific well-circumscribed mass. On ultrasound a phyllodes tumour presents as a lobulated well-defined heterogeneous echogenic mass with internal cystic alterations and septations. Vascularisation is usually present in the solid components. Magnetic resonance imaging (MRI) shows a well-defined, lobulated mass with internal septations. The cystic components are hyperintense on T2-WI. The solid components enhance after contrast administration, shown as hyperintensity on T1-WI. Kinetic curve pattern can be gradual slow or rapid enhancement [1].
Primary differential diagnosis consists of fibroadenoma, which is the most frequent fibroepithelial tumour. Clinical arguments for phyllodes are peak incidence at the age of 45 years compared with fibroadenoma before 30 years. Rapid growth is also suspicious for phyllodes tumour. Mammography and ultrasound are insufficient to differentiate phyllodes tumour from fibroadenoma [2]. The presence of fluid-filled, elongated spaces or clefts within a solid mass are characteristic, but not pathognomonic for phyllodes tumour. MRI for differentiation has been suggested in literature with conflicting results [3, 4]. MRI can be useful for evaluation of internal structure, enhancement pattern and kinetic curve assessment when differentiating with other well-circumscribed malignant tumours as intracystic / invasive papillary carcinoma or metaplastic carcinoma [5]. Preoperative MRI studies [2, 6] describe various phyllodes tumour characteristics to correlate with histological grade: tumour size, internal non-enhanced septations, silt-like changes in enhanced images, signal changes from T2-weighted to enhanced images, irregular wall, tumour SI lower than or equal to normal tissue on T2-WI and low ADC (equals stromal hypercellularity).
Diagnosis is nevertheless based on anatomopathology and pre-operative tissue sampling is necessary. Fine needle aspiration is inaccurate and even core biopsy has moderate sensitivity due to tumour heterogeneity causing inadequate sampling [7]. These factors render pre-operative diagnosis challenging.
Surgery is the only therapeutic option since phyllodes tumour is not proven to be sensitive to radio- or chemotherapy. Wide resection margin of at least 1 cm is advocated to prevent local recurrence. Breast conservative surgery is preferred if possible [7]. The prognosis is good; the tumour rarely metastasises.

Differential Diagnosis List

Final Diagnosis

Borderline phyllodes tumour

URL:	https://www.eurorad.org/case/9265
DOI:	10.1594/EURORAD/CASE.9265
ISSN:	1563-4086