Giant left breast hamartoma in a 45-year-old woman

Abstract

This is a case of a woman in her fifth decade of life who presented with a lump in her left breast. The patient underwent extensive breast investigations which did not confirm one particular diagnosis. The lesion was excised, and histological findings confirmed the diagnosis of a giant breast hamartoma. This case is interesting due to the largeness. As well as this, giant breast hamartomas are uncommon, and this case highlights the difficulty in their diagnosis and frequent misdiagnoses, potentially contributing to their reported low incidence rates. Diagnosis is difficult due to the complex appearance of the mass on imaging, raising the possibility of malignancy. Core biopsy is unremarkable, with the final diagnosis only possible on histological examination of the resected mass.

Background

This case describes a 45-year-old woman who developed a large hamartoma in her left breast.

WHO defines breast hamartomas as ‘a well demarcated, generally encapsulated mass, composed of all components of breast tissue’.¹ Giant breast hamartomas can vary considerably in their composition. This makes diagnosis of these lesions difficult; frequently giant breast hamartomas are misdiagnosed as fibroadenomas both on clinical and imaging assessment. Correct diagnosis relies on combining the results of clinical, radiological and histopathological investigations. One special investigation alone can often be misrepresentative. In this instance, the diagnosis was not confirmed until histological findings after the lesion was completely excised. Core biopsy is non-diagnostic—revealing normal breast tissue. Indeed, a core biopsy with this result may raise the suspicion of hamartoma. The complexity of the imaging findings can suggest possible soft-tissue malignancy.

Additionally, this report is notable as hamartomas are uncommon and giant types are rare, only representing about 0.7% of benign breast tumours in women.¹ It is thought that this figure is low due to underdiagnosis and under-reporting.

Case presentation

A 45-year-old woman was referred by her general medical practitioner regarding a palpable lump in her left breast. She reported it as present for 10 days and had never had a mammogram.

On examination, there was a discrete lump in her left upper outer quadrant of the left breast. The left breast was larger than the right. There was no tenderness and there were no palpable axillary nodes.

Investigations

Mammograms showed an enlarged left breast containing an encapsulated mass of mixed fat/soft-tissue density with lobulated serpiginous areas of opacity centrally (see figure 1). Additionally, there was an ill-defined spiculated area of increased density deep and medial to the left nipple measuring 3×2 cm.

Figure 1.

Lateral oblique mammogram of right and left breast, showing an encapsulated mass of soft tissue/fat density within the left breast.

Ultrasound confirmed the area medial and deep to the left nipple, appearing as a poorly defined area of reduced echogenicity. It also revealed an unusual branching network of tubular avascular hypoechoic structures with echogenic walls extending throughout the left breast corresponding to the palpable abnormality in the upper left breast (see figure 2).

Figure 2.

Ultrasound of left breast mass showing a complex encapsulated mass (black arrows show anterior capsule) of mixed texture—echogenic/fatty containing tubular hypoechoic structures (white arrows).

The patient underwent an ultrasound-guided core biopsy from the area of altered texture deep and medial to the left nipple; this was reported as benign breast tissue. At one edge of the core biopsy, a focus of mild chronic inflammation surrounding ducts was identified. There was no evidence of ductal carcinoma in situ or invasive malignancy.

The patient proceeded to contrast enhanced MRI (figures 3 and 4). This demonstrated a complex and encapsulated mass within the left breast (figure 3), containing soft tissue and fatty components and no definite evidence of malignancy or pathological enhancement.

Figure 3.

MRI axial T1-weighted image of the breasts. MRI confirms an encapsulated mass within the left breast (white arrows show the capsule), of mixed signal, mainly fat density, but containing mixed signal foci.

Figure 4.

Axial postcontrast fat-saturated MR image of the breasts, confirms the same internal foci of enhancement within the left breast mass.

Treatment

The consensus opinion at the multidisciplinary team meeting was that while the lesion did not look overtly malignant, it was however unusual and warranted excision for definitive diagnosis.

Outcome and follow-up

The mass was excised completely and intact via a medial incision (see figure 5). Histology reported a circumscribed fatty tissue mass weighing 382 g and measuring 10 cm×6 cm×5 cm. Multiple histological sections taken from this breast tissue show features in keeping with hamartoma; the tissue consists predominantly of mature fat mixed with varying proportions of breast parenchyma showing nodular aggregate of lobular breast tissue with occasional stromal fibrosis (figures 6 and 7). There was no evidence of ductal carcinoma in situ, lobular carcinoma in situ or invasive malignancy.

Figure 5.

The left breast during surgical excision. The mass can be seen extruded via a medial incision. It is encapsulated and intact.

Figure 6.

Histological findings: demonstrates the nodular aggregates of lobular breast tissue. H&E staining of 20 magnification. Arrow A shows mature adipose tissue. Arrow B shows benign glandular tissue.

Figure 7.

Demonstrate distorted breast ducts accompanied by fibrotic stroma. H&E staining of 40 magnification. Arrow shows dilated breast duct.

The patient was reviewed once in clinic with the histology results; she was reassured of the benign nature of the lesion and discharged.

Discussion

Giant breast hamartomas are rare and usually occur in perimenopausal women during the fourth or fifth decades of life.¹ However, they can occur at any age with a case reported by Venkatesh and Harish in a 14-year-old girl.² Typical presentation is of a painless, palpable breast mass which may vary in firmness; there may or may not be significant associated breast asymmetry.³

Although widely regarded as benign, there have been cases reported of invasive ductal carcinoma⁴ and invasive lobular carcinomas⁵ arising within hamartomas. This increases the importance of correct diagnosis and treatment.

As demonstrated by this case, giant breast hamartomas can reach large sizes. Cazorla and Arentz reported two cases of particularly large giant breast hamartomas measuring 15 cm×13 cm and 20 cm.⁶ The resulting breast asymmetry may impact on the patient’s self-esteem and psychological well-being, as well as causing physical pain and discomfort due to the weight and compression of surrounding structures.

Giant breast hamartomas can be difficult to diagnose. Findings on mammograms, ultrasound and MRI are often not specific and can mimic soft-tissue malignancy. The diagnosis was only confirmed after histological examination of the excised mass. This is in keeping with other published cases.³

Histologically, hamartomas were originally defined as a clinically discrete nodule consisting of varying amounts of epithelial elements in a fibrofatty stroma. It has suggested that the presence of fat and lobular distribution is the distinguishing features between a hamartoma and a fibroadenoma.⁷ Ninety per cent of hamartomas contain adipose tissue, making up 10%–20% vol within the hamartoma. The mass may contain pseudoangiomatous stroma and epithelial changes including hyperplasia, cystic changes or metaplasia.³ Core biopsy is typically not diagnostic, often finding normal breast tissue.

The mammographic appearance varies due to the varying proportions of fat, glandular and fibrous tissue within the mass. If a mammogram reveals a well-circumscribed mass of uniform fat density, the most likely differential diagnosis is a lipoma or a hamartoma.⁸ Characteristic features of giant breast hamartomas on mammograms include a non-homogenous compressible mass with dense nodules of fibrous connective tissue. These lesions are often pseudoencapsulated as a result of displacement of breast parenchyma. Typical mammographic appearance is often described as a ‘slice of salami’, in reference to lobular densities within surrounding fat. Malignancy may be suspected if pleomorphic calcification or spiculated opacities are seen.⁹

Ultrasound can be used to help differentiate whether the mass is a simple cyst, fat based or a complex mass or a solid mass.⁸ Ultrasound of hamartomas shows echogenic fibrous components and sonolucent fat. There is often a mixed internal echo pattern, and sharp borders with the displacement of surrounding structures; findings are however non-specific.³

MRI supports this pattern, showing a mixed mass, internal fat, a well-defined, smooth, pseudoencapsulated hypoechoic rim. This is in keeping with the structure of a hamartoma with no pathological or malignant-type enhancement.³

In summary, giant breast hamartomas can be difficult to diagnose despite the use of multiple breast imaging modalities and core biopsy. Early diagnosis is preferred to confirm no evidence of malignancy. Treatment usually entails surgical excision.

Learning points.

• Breast hamartomas have varying imaging features and can be difficult to diagnose with imaging and core biopsy, usually requiring excision for definitive diagnosis.

• Although widely regarded as benign, there have been published cases of carcinoma arising within hamartomas, making correct diagnosis and excision paramount.

• Giant breast hamartomas can reach very large sizes potentially leading to physical and psychological discomfort to the patient.