Abstract
Introduction
Aneurysms of the internal mammary artery, also known as the internal thoracic artery, are uncommon. Surgical repair of these aneurysms are crucial, as they may rupture and result in life-threatening hemothorax. Aneurysms of the internal mammary artery are most commonly caused by trauma to the chest, sternotomy, or pacemaker implantation [3]. When none of the aforementioned risk factors can be associated with the development of the aneurysm, a vasculopathy must be ruled out as the underlying etiology. The vascular pathology can either be inflammatory in nature or be secondary to a genetically acquired defect. As such, patients with Marfan’s Syndrome, Ehlers-Danlos, or Neurofibromatosis Type 1 are more prone to develop aneurysms of the internal mammary artery.
This is a case report in which a 56-year-old female presented with a pulsatile breast mass that was initially concerning for malignancy. As far as we know, this is the first case report that describes a peripheral aneurysm of the internal mammary artery. These aneurysms are generally more central rather than peripheral. Furthermore, these aneurysms generally have an attributable cause, whether it is trauma, iatrogenic, or secondary to a vascular abnormality. Our patient exhibited none of these risk factors. As such, this is a highly atypical presentation of an already rare disease.
Case report
A 56-year-old female with history of hypertension, osteopenia, and rheumatoid arthritis presented for surgical consultation secondary to a three-month history of right breast mass. She initially noted a bruise on her breast which was associated with a palpable, tender breast mass. She reported that the size of the mass had been unchanged over the past three months, and that the bruising had resolved. However, the mass itself had remained, so she presented for further evaluation. She denied any history of breast trauma. She had no previous surgeries performed.
In terms of risk factors for breast cancer and gynecologic history, this patient was gravida 1, para 2 and breastfed her twins. She underwent in-vitro fertilization at the age of 44. Her age of menarche was at 13 and her last menstrual period was 8 years ago. She has a negative family and personal history of breast and ovarian carcinoma. She denied use of oral contraceptive pills.
On physical examination, there was a palpable, slightly pulsatile mass in the right breast at the 1 o’clock position in the upper inner quadrant, measuring approximately 1.5–2 cm. There was no axillary or supraclavicular adenopathy and her liver was not palpable.
Her mammogram revealed an indeterminate mass, but the ultrasound images were suggestive of a partially thrombosed aneurysm within the breast. CT angiogram was performed in order to further delineate the origin of the mass, which showed a one-centimeter peripheral aneurysm involving the left internal mammary artery in the superior medial right breast area. A halo was present surrounding the aneurysm, thought to be related to a peripheral thrombus.
The patient was taken to the operating room for definitive excision of the aneurysm. Final pathology showed a false aneurysm with adjacent thrombus formation.
Discussion
The internal mammary artery arises from the subclavian artery and is the primary blood supply to the anterior chest wall and the breasts. Its branches include the superior epigastric artery, musculophrenic artery, pericardiacophrenic artery, as well as thymic, mediastinal, sternal, intercostal, and perforating branches. In certain situations, flow through the vessel can be as high as 175 mL/min [3]. Rupture of this artery can lead to significant hemodynamic instability and hemorrhage/hemothorax. With these complications in mind, repair of internal mammary aneurysms becomes crucial and potentially lifesaving.
When searching for the etiology of this patient’s IMA aneurysm, it is important to consider that she had no history of instrumentation, trauma to the chest wall, or pertinent medical history. There is, of course, also the probability that the patient has an extremely remote history of trauma to the chest that she could not recall. This may be a very late manifestation of previous trauma to the chest wall, although this would be less likely given how slowly the aneurysm would have to grow to present so late. The aneurysm in our patient appears to be idiopathic in nature. Given that there are no published reports of peripheral internal mammary artery aneurysms to our knowledge, data regarding this topic was extremely limited.
From a vascular perspective, these lesions are most common in patients who have a history of vasculitis, such as Kawasaki Disease, or a connective tissue disorder such as Marfan’s Disease [4]. As mentioned, our patient had no history of any vascular disorders and did not show any signs or symptoms of having any on physical exam.
When discussing treatment options, the mainstays of treatment include embolization or ligation. Stent graft exclusion of this aneurysm was not an attractive option given its more peripheral location. However, there have been cases reported in the literature where stent graft repair has been used a viable treatment modality for repair of internal mammary aneurysms [5]. This could be a consideration for future repairs.
There are two other case reports available in the literature in which patients presented with idiopathic internal artery aneurysms [3,6]. However, both these case reports involved central aneurysms and not peripheral. The case report by Piffaretti et al. demonstrated cystic medial necrosis on final pathology, which would explain the cause of the aneurysm [5]. Final pathology on our patient failed to reveal any obvious vascular abnormalities.
There is another case report in the literature that describes a patient with the SMAD -3 mutation who presented with an internal mammary artery aneurysm. While this patient was not tested for the aforementioned mutation, it is possible that she has a mutation in a gene encoding connective tissues. Similarly, there have been case reports describing internal mammary artery aneurysms in patients with Loeys-Dietz Syndrome [1]. This is a condition wherein the patient develops both central and peripheral arterial aneurysms and dissections. In our patient, it may be worthwhile to test for connective tissue disorders.
In conclusion, internal mammary artery aneurysms are exceedingly rare and mandate operative intervention. Generally, an underlying cause can be identified. Furthermore, these lesions are more centrally located versus at the periphery, where they are palpable, pulsatile masses. Our patient presented with a peripheral, idiopathic internal mammary artery aneurysm and underwent successful surgical excision.