Elastofibroma Dorsi in a Patient with Right Breast Carcinoma: A Potential Diagnostic Pitfall

Introduction

Elastofibroma dorsi is a rare, benign soft tissue pseudotumour that typically arises in the infrascapular region, deep to the serratus anterior and latissimus dorsi muscles. 1 It is most commonly observed in elderly individuals, with a distinct female predominance. The lesion is widely considered reactive rather than truly neoplastic in origin. 2

The proposed pathogenesis involves repetitive mechanical friction between the inferior pole of the scapula and the posterior thoracic wall, leading to fibroelastic tissue proliferation interspersed with fatty streaks. 1,2 This explains both the characteristic infrascapular location and the internal architectural pattern observed on imaging studies. A hereditary predisposition has also been suggested in a minority of cases. 3

Despite its benign nature and indolent clinical course, elastofibroma dorsi assumes considerable importance in oncologic imaging. In patients with known malignancies such as breast carcinoma, the lesion may mimic soft tissue metastasis due to its chest wall location and soft tissue density on computed tomography (CT). 4,5 Accurate recognition is therefore crucial to prevent misinterpretation and unnecessary intervention.

Case Report

An 80-year-old female, a known case of right breast carcinoma, was referred for staging evaluation.Contrast-enhanced CT of the thorax revealed an illdefined, non-encapsulated soft tissue lesion in the right infrascapular region. \

The lesion was located deep to the latissimus dorsi muscle and serratus anterior muscle, and superficial to the ribs and intercostal muscles. Its anatomical relations were as follows:

• Anterior relation: Serratus anterior muscle
• Posterior relation: Latissimus dorsi muscle
• Medial relation: Rib cage and intercostal muscles
• Lateral relation: Subcutaneous fat plane

The lesion demonstrated a lenticular configuration with poorly defined margins and showed internal linear streaks of fat attenuation within a soft tissue matrix, producing a characteristic “striated” appearance. 6,7 No calcification, necrosis, or adjacent bony erosion was noted. Given its typical location, morphology, and internal fat streaks, a diagnosis of elastofibroma dorsi was favoured over metastatic disease.

Discussion

Elastofibroma dorsi is a benign pseudotumour with characteristic imaging features that allow confident diagnosis in the majority of cases. 7 It is most commonly located in the infrascapular region, typically unilateral, though it may be bilateral in up to 60% of cases when both sides are systematically imaged. 4 On CT, the lesion appears as a poorly defined soft tissue mass with attenuation similar to skeletal muscle, interspersed with linear fat densities, reflecting its internal fibroelastic architecture. 6,7 On magnetic resonance imaging (MRI), it demonstrates alternating fibrous (low signal intensity) and fatty (high signal intensity) components on both T1and T2-weighted sequences, producing a layered or striated appearance.

These imaging features directly reflect the histological composition of the lesion:

• Fat streaks: Entrapped adipose tissue within fibrous proliferation
• Poor margins: Reactive, non-encapsulated growth pattern
• Typical location: Repetitive scapulothoracic friction leading to fibroelastic hyperproliferation

Histologically, the lesion is composed of abnormal elastic fibres embedded in a collagenous stroma with interspersed adipose tissue. 2 Immunohistochemically, it demonstrates a non-neoplastic, reactive phenotype. 9

In oncologic patients, particularly those with breast carcinoma, this lesion may be misinterpreted as a soft tissue metastasis owing to its chest wall location and soft tissue density. 5,10 However, metastases can be distinguished by the following features:

• More aggressive or infiltrative margins
• Possible adjacent bone destruction or cortical erosion
• Absence of internal fat streaks
• Variable or intense contrast enhancement without fat signal

Recognition of elastofibroma dorsi is essential to avoid unnecessary biopsy, incorrect oncological staging, and overtreatment. 11,12 When imaging features are pathognomonic, no further investigation or intervention is required. Surgical excision is reserved for symptomatic cases only.