Breast Hamartoma Case Study: 49-Year-Old Female Presenting for Breast Cancer Screening

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 Breast Hamartoma Overview

Cause and Etiology

  • Breast hamartomas are benign, tumor-like malformations composed of normal breast elements—glandular, fibrous, and fatty tissue—in a disorganized arrangement.
  • The exact cause is unknown, but they are believed to result from developmental anomalies during breast tissue formation.
  • They are non-neoplastic and not caused by external factors like trauma or infection.

Pathophysiology

  • Hamartomas arise from an abnormal proliferation and organization of native breast tissue components.
  • They contain varying proportions of adipose, fibrous, and glandular tissue, often surrounded by a thin pseudocapsule formed by compressed surrounding tissue.
  • Some variants may contain:
    • Smooth muscle (myoid hamartomas)
    • Cartilage or bone (very rare)
  • Despite the benign nature, rare malignant transformation has been reported (e.g., ductal carcinoma in situ arising within a hamartoma), although extremely uncommon.

Epidemiology

  • Occurs in adult women, predominantly between the 4th and 6th decades of life.
  • Incidence is low: it represents about 0.7–4.8% of all benign breast tumors.
  • More frequently found in postmenopausal women, but can occur in younger patients.
  • It can be underdiagnosed, especially in dense breasts or when small.

Clinical Presentation

  • Most hamartomas are asymptomatic and discovered incidentally on imaging.
  • When symptomatic:
    • Painless, soft to firm, mobile breast mass
    • May grow slowly
    • Occasionally, breast asymmetry or local distortion
  • Usually non-tender and not associated with nipple discharge or skin changes.

Imaging Features

🔍 Mammography (most characteristic imaging modality):

  • Well-circumscribed, oval or round mass
  • “Breast within a breast” or “slice of salami” appearance
    – due to the mixture of fat and soft tissue density
  • A thin radiolucent halo may be present (compressed surrounding tissue)

🔍 Ultrasound:

  • Heterogeneous echotexture with well-defined margins
  • Hypoechoic or isoechoic relative to the surrounding tissue
  • May show internal fat and fibrous septa

🔍 MRI (less commonly needed):

  • Well-circumscribed lesion with signal intensity reflecting fat and fibroglandular tissue
  • Useful in complex or equivocal cases

Treatment

  • No treatment is required if the diagnosis is certain and the lesion is asymptomatic.
  • Surgical excision may be considered in:
    • Rapid growth
    • Atypical imaging features
    • Diagnostic uncertainty
    • Patient anxiety
    • Suspicion of malignancy or atypia within the lesion

Prognosis

  • Excellent prognosis; breast hamartomas are benign with no inherent malignant potential.
  • Recurrence is rare after excision.
  • Surveillance is sufficient in most cases.
  • Malignant transformation is extremely rare, but histopathological confirmation is essential in atypical cases.
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Case study: 46-Year-Old Female Presenting for Breast Cancer Screening - Breast Hamartoma

History and Images

  1. A 46-year-old female presented for breast cancer screening.

  2. Several years ago, a mass was discovered in the left breast, and a biopsy was performed.

  3. Mammography and tomography were conducted.

  4. The bilateral craniocaudal (CC) and mediolateral oblique (MLO) images are shown below.

Quiz 1:

  1. Where is the prominent finding located?
    (1) Upper outer quadrant of the left breast
    (2) Upper inner quadrant of the left breast
    (3) Lower outer quadrant of the left breast
    (4) Lower inner quadrant of the left breast

  2. The mass contains internal fat.
    (1) True
    (2) False

  3. The mass is oval-shaped with defined borders.
    (1) True
    (2) False

  4. What is the next step in management?
    (1) Ultrasound
    (2) Short-term follow-up
    (3) Request prior imaging for comparison
    (4) Biopsy

Additional History and Images

  1. Previous screening images were obtained.

  2. The mass has remained stable on mammography for several years.

  3. The previous breast ultrasound images are shown below.


Quiz 2:

  1. What is the most appropriate description of the mass's echotexture?
    (1) Anechoic
    (2) Hypoechoic
    (3) Isoechoic
    (4) Hyperechoic
    (5) Heterogeneous

  2. What is the most likely diagnosis?
    (1) Hamartoma
    (2) Fat necrosis
    (3) Lipoma
    (4) Galactocele

Findings and Diagnosis

Findings

Mammography: Areas of dense fibroglandular tissue are scattered in the left breast. An oval-shaped mass with well-defined borders is present in the upper outer quadrant of the left breast, with an associated biopsy clip. This mass contains both fat and fibroglandular tissue.

Ultrasound: An oval-shaped, well-defined heterogeneous mass, measuring approximately 3.4 x 1.2 x 3.4 cm, was observed in the left breast at the 3 o'clock position, about 10 cm from the nipple. The mass contains both breast parenchymal and fat tissue.

Differential Diagnosis

  • Breast lipoma

  • Fibroadenoma

  • Phyllodes tumor

  • Fat necrosis

  • Intramammary lymph node

  • Breast hamartoma

Diagnosis: Breast hamartoma

Discussion

Breast Hamartoma

Pathophysiology
Breast hamartomas, also known as fibrolipomas, are benign, slow-growing tumors composed of both fat and fibroglandular tissue. The size of a hamartoma typically ranges from 2 to 5 cm. The pathogenesis remains unclear, but certain genetic conditions, including PTEN mutations and Cowden syndrome, are associated with an increased risk of developing breast hamartomas.

Epidemiology
The reported incidence is less than 1%, and hamartomas primarily occur in premenopausal and perimenopausal women, with an average age of diagnosis around 45 years. Hamartomas are very rare in men and account for approximately 5% of benign breast tumors.

Clinical Presentation
Patients are often asymptomatic; however, larger breast hamartomas may present as a palpable mass. Hamartomas are typically painless.

Imaging Features

  • Mammography: The mass appears as an oval-shaped, well-defined lesion containing both fat and glandular tissue. It often has a pseudocapsule, and the localized area may contain components similar to normal breast tissue, giving it a characteristic "another breast within the breast" appearance.

  • Ultrasound: While mammography is often useful for diagnosis, ultrasound plays a crucial role in differentiation. In young patients with palpable breast hamartomas, ultrasound may be performed as an initial examination. On ultrasound, hamartomas appear as oval-shaped, well-defined masses with heterogeneous echotexture. The pseudocapsule may sometimes appear subtle and thin with an echogenic border.

Management
Although hamartomas are benign, rare cases of breast cancer may develop within them due to the presence of fibroglandular tissue. Therefore, if there are suspicious calcifications, masses, or other abnormal findings within the hamartoma, or if the mass grows significantly, further investigation through regular monitoring or biopsy is recommended. If symptomatic, hamartomas can be surgically excised.

References

(1)      Sevim Y, Kocaay AF, Eker T, et al. Breast hamartoma: A clinicopathologic analysis of 27 cases and a literature review. Clinics (Sao Paulo). 2014;69(8):515-523.

(2)      Tazeoğlu D, Dağ A, Arslan B, Berkeşoğlu M. Breast hamartoma: Clinical, radiological, and histopathological evaluation. Eur J Breast Health. 2021;17(4):328-332.

(3)      Tse GM, Law BK, Ma TK, et al. Hamartoma of the breast: A clinicopathological review. J Clin Pathol. 2002;55(12):951-954.

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