Pipe bearer’s lump: Post-traumatic pseudolipoma of bilateral shoulder

INTRODUCTION

Pseudolipomas are painless, unencapsulated adipose tissue masses, considered either localized subcutaneous fat hypertrophy or benign tumors. When associated with acute or prolonged blunt trauma, they are termed post-traumatic pseudolipomas (PTPLs) or lipohypertrophy.^[1,2] The leading pathogenic theory is the inflammatory proliferation model, where trauma-induced cytokines stimulate pre-adipocyte differentiation into mature adipocytes.

The role of trauma in the development of lipoma was first reported by Adair et al. in 1932, citing two trauma-induced cases.^[3] We present a patient with bilateral shoulder pseudolipomas due to the repetitive load secondary to his occupation.

CASE REPORT

A 28-year-old male presented with painless, symmetric shoulder swelling persisting for 5 years [Figure 1]. He had discontinued his daily work involving heavy pipe carrying due to the lesions. Examination showed firm, non-tender masses over the acromioclavicular joints with normal, stretched skin, no redness or warmth, and unrestricted shoulder movements.

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Figure 1:

Photographs of the patient showing symmetrical swellings in the acromioclavicular regions bilaterally (black arrows).

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Ultrasound revealed ill-defined hyperechoic thickening of subcutaneous fat without a discrete mass or definable capsule and with no vascularity [Figure 2].

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Figure 2:

(a) Ultrasound image shows thickening of the subcutaneous fat plane (asterisk) with heterogeneous echotexture, minimal internal vascularity, and internal septations. (b and c) show subcutaneous fat thickening at the site of lesion compared to adjacent normal region (asterisks).

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Magnetic resonance imaging (MRI) and computed tomography revealed subcutaneous lesions above the acromioclavicular joints with signal intensity and density consistent with fat [Figures 3 and 4]. On MRI, the lesions were hyperintense on T1-weighted (T1w) images with signal suppression on fat-suppressed sequences. Fibrous septae and fat stranding were noted without a definitive capsule. Differential diagnoses included lipomatous tumors, lipodystrophy, subcutaneous fat necrosis, resolving hematoma, and pseudolipoma. The patient reported frequent carrying of heavy metallic pipes on his shoulders, corresponding to the lesion sites.

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Figure 3:

(a) Axial, (b) coronal and (c) sagittal non-contrast computed tomography images show moderately well-defined subcutaneous fat density lesions (asterisks) with internal soft tissue stranding bilaterally superior to the acromioclavicular region with no definite capsule.

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Figure 4:

(a) Coronal T2 weighted, (b) sagittal T1 weighted and (c) sagittal fat suppressed T1 weighted magnetic resonance imaging images reveal a moderately well-defined subcutaneous lesion (asterisks) with fat signal intensity and internal septations superior to the acromioclavicular region. There is no evidence of a capsule.

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A diagnosis of bilateral symmetric PTPLs in the shoulder regions secondary to repetitive microtrauma caused by carrying heavy loads was made.

DISCUSSION

PTPLs can develop after acute or chronic trauma and are frequently linked to repetitive load and strain. These lesions are most commonly found on the lower extremities, gluteal, and trochanteric regions. The location of the lesion in the shoulders in this patient is not a very common presentation and is due to the repetitive load of bearing the weight of pipes linked with his occupation.

Galea et al., in a review of 124 PTPL cases, found a female predominance (female-to-male ratio 3.8:1) and a predilection for the lower limbs. Reported causes included motor vehicle accidents, blunt trauma, falls, and iatrogenic factors such as injections and liposuction.^[4,5]

Similar cases have been linked to occupational activities. Athletes and laborers may develop lipomas in the nuchal region from repetitive strain, such as tar barrel rolling or weightlifting.^[6,7] Abnormal fat accumulation on the shoulders has been noted in festival participants in Japan and Italy, wine porters, brewery workers, and heavy handbag carriers.^[8-10] Ramoutar et al. also described large ventral abdominal pseudolipomas in a surfer.^[11]

Madelung disease/Launois–Bensaude syndrome, or benign symmetric lipomatosis, is a rare metabolic disorder characterized by symmetric, non-encapsulated fat deposits around the neck, shoulders, and upper trunk. First described by Benjamin Brody in 1846, it resembles pseudolipomas.^[12]

PTPLs typically appear as non-enhancing, unencapsulated subcutaneous fatty masses. On MRI, they resemble mature adipose tissue, appearing hyperintense on T1w, intermediate-hyperintense on T2-weighted (T2w), and suppression on short tau inversion recovery (STIR) sequences.^[13] They lack a true capsule, blending with surrounding tissues. Reactive fibrous tissue or septa within the mass appear hypointense on T1w and T2w images and hyperintense on STIR.^[14] Their typical location over pressure points, such as the acromioclavicular joints, aids in diagnosis.

Differential diagnosis includes benign and malignant fat-containing lesions, such as atypical lipomatous tumors.^[8] A detailed clinical history, including trauma or occupational factors, is crucial. Deep-seated lesions, like those in the retroperitoneum or thigh musculature, may require biopsy to exclude potential liposarcoma, whereas subcutaneous lesions over bony prominences, likely pseudolipomas, are usually monitored with imaging.

PTPL is typically managed conservatively, with surgical excision or liposuction considered for cosmetic concerns. While the natural course of untreated PTPL is unclear, malignant transformation to liposarcoma has not been reported.

CONCLUSION

“Pipe bearer’s lump” describes localized shoulder pseudolipomas caused by repetitive microtrauma from carrying heavy loads such as pipes or rods. Their rarity and unpredictable occurrence highlight the importance of a detailed clinical history for appropriate clinico-radiological correlation.