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Abstract
Parosteal lipomas are typically seen in adults and affect mostly the diaphysis of the long bones of the upper and lower limbs. Only a few cases have been reported in children until now and none were reported involving ribs. A female adolescent patient presented with swelling on the left upper back over the scapular region for the past 4 years without any neurological deficit. MRI revealed a hyperintense lesion on the left paravertebral region extending from D5 to D12 and into the intercostal space, causing it to widen. The patient underwent surgical excision. The lipomatous mass was seen entering in to the intercostal space, causing it to widen. However, the pleura was not breached. In this report, we have performed a literature review compiling all cases of parosteal lipoma affecting the ribs.
- Paediatric Surgery
- General surgery
- Radiology
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Background
Parosteal lipomas are rare, solitary, slow-growing benign tumours, arising from the mature adipose tissue that is contiguous with the underlying periosteum of bones, without originating from it. They account for less than 0.3% of all lipomatous lesions.1 2 They are typically seen in patients above 40–60 years of age and mostly affect extremities. Only a few cases of parosteal lipoma have been reported in children until now. Here, we reported a case of parosteal lipoma of rib, which is an unusual location, in a child and reviewed the literature.
Case presentation
A female child in her adolescence presented with swelling on the left upper back over the scapular region for the past 4 years. The swelling was noticed insidiously and was gradually increasing in size, not associated with pain, no loss of function or history of any neurological deficit. There was no history of previous trauma. On clinical examination, a single swelling measuring about 12×11 cm was observed over the left scapular region extending 6 cm below the head of humerus superiorly, medially extending up to the midline, laterally up to the posterior axillary line, and inferiorly up to the seventh intercostal space. The swelling was firm in consistency and non-tender, had smooth overlying surface and was immobile. Distal pulse and neurological examination of the left upper extremity were normal.
Investigations
Plain radiograph of the right chest revealed normal study. MRI of the left scapula revealed a hyperintense lesion (12×1.7×12 cm) on the left paravertebral region extending from D5 to D12, which is suppressed on STIR sequence (figure 1). The lesion was also extending into the fifth intervening intercostal space, causing its widening due to mass effect. Visualised vertebral bodies showed normal signal intensity and morphology. The final impression of MRI was lipoma. Tru-cut biopsy was performed which was suggestive of lipoma.
Axial T1WI (A) and T2WI (B) showing hyperintense lesion (marked by white arrow) in the left paravertebral region extending from D5 to D12 levels, which is suppressed on fat suppressed sequence, that is, stir (C). Corresponding coronal (D) and sagittal (E) T2WI showing the extent of the lesion. Protrusion of lipoma causing intercostal widening is marked by yellow arrow (WI—weighted image, STIR—short τ inversion recovery sequence).
Differential diagnosis
Based on clinical examination, lipoma, lipoblastoma and liposarcoma were considered as differential diagnosis. However, radiology and histopathology confirm the diagnosis of lipoma only.
Treatment
The patient underwent complete surgical excision. The mass was excised from the surrounding soft tissues and underlying periosteum to which it was densely adhered. The fifth intercostal space was widened and the mass was seen entering into the intercostal space but the pleura was not breached (figure 2).
Intraoperative photograph showing adhesions to periosteum of rib (marked by multiple white arrows) and widening of intercostal space (marked by yellow arrow) after removal of the lipomatous mass.
Outcome and follow-up
Histopathology of the excised specimen was given as lipoma. The patient recovered without any complication and returned to school 2 weeks after the surgery. She was doing well at 6 months follow-up and is still asymptomatic.
Discussion
The term ‘periosteal lipoma’ was first used by Seering in 1836 and was initially thought to arise from periosteum. Power first used the term ‘parosteal lipoma’ in 1888 to underline that the lesion is near the bone but does not necessarily develop from it because the periosteum does not contain fat cells.1 Parosteal lipomas have been reported in patients with age ranging from 3 months to eighth decade; however, they are typically seen in middle-aged patients above 40 years of age and affect both sexes equally.3 They usually affect extremities and develop in the diaphysis of long bones, and the most common sites are the femur, radius, tibia and humerus.1 2 However, the lesion has been reported to originate in the spine, scapula, ribs, clavicle, metacarpals, metatarsals, pelvis, mandible and skull.3 4
Clinical presentation depends on the site of origin and the patients typically present with a slow-growing mass that is painless, non-tender and immobile.2 When compared with other lipomatous lesions, patients with parosteal lipomas are more likely to develop motor or sensory abnormalities and muscle atrophy due to nerve compression, and these deficits are most typically linked to forearm lesions that damage the posterior interosseous nerve.5
Parosteal lipomas typically have distinctive radiological characteristics. It demonstrates intimate association with the periosteum and osseous reaction is present in the underlying bone in up to 60% of cases.6 Typically, the reaction is hyperostotic and manifests as cortical thickening, sclerosis, calcification and osseous excrescence.6 Less commonly, the reactive bone change can manifest as smooth cortical scalloping or bowing, but bone destruction has not been reported.6 7 These cortical anomalies show no medullary or cortical continuity with the underlying bone. A juxtacortical radiolucent lipomatous mass with varying degrees of septation, along with surface bone productive changes ranging from very subtle to obvious cortical thickening and variably sized ossific protuberances or excrescences, is the main radiographic feature of parosteal lipoma.1
MRI is considered superior to CT for preoperative planning. The tumour is identified as a juxtacortical mass with signal intensity identical to that of subcutaneous fat, regardless of pulse sequence. These lesions almost always have heterogeneity, which is consistent with the pathogenic elements of the lesion. The cartilaginous components in parosteal lipoma are areas with moderate signal intensity on T1-weighted images and high signal intensity on T2-weighted images.1 Osseous components are represented as hypointense T1- and T2-weighted regions. The cartilaginous parts of the parosteal lipoma are areas with moderate signal intensity on T1-weighted images and high signal intensity on T2-weighted images.1 With low signal intensity strands on T1-weighted images that grow stronger in signal intensity on the long TR images, fibrovascular septa may cause a lobulated appearance of the fat component, especially with fat suppression. Increased fat striations in the afflicted muscle are a sign of adjacent muscular atrophy, which is brought on by concomitant nerve entrapment.1
Pathologically, a parosteal lipoma is usually a multilobulated mass circumscribed by a thin fibrous capsule and is usually well encapsulated with broad based attachment to the underlying bone. Histologically, they consist of mature adipocytes without cellular atypia. There are no reports of malignant transformation.
The treatment of choice for parosteal lipoma is surgical excision, especially in situations where nerve entrapment is present. Complete surgical excision is to be performed before irreversible muscle atrophy occurs. Particularly at sites with osseous proliferation, parosteal lipomas are strongly adhered to the underlying periosteum. Subperiosteal dissection or if required, segmental resection of bone may be necessary for complete removal.
We reviewed the English literature through PubMed search and found only nine studies describing parosteal lipoma affecting the ribs in 10 patients (table 1).8–16 All were adults (ranging from 20 years to 64 years) except in one case, where the lesion was present since childhood and slowly increasing in size. Males and females were affected equally with duration of the mass ranging from 2 months to 14 years. Additionally, both side ribs were affected equally with the third and fourth ribs being more commonly affected. Surgical excision was curative in all cases without any recurrence. Ours is the first case of parosteal lipoma of ribs to be reported in a child that was managed successfully with surgical excision.
Reports of parosteal lipoma of ribs in English literature
Learning points
Parosteal lipoma has been rarely reported in childhood. The rib is an extremely rare site for developing parosteal lipoma especially in children.
High index of suspicion should be observed for all lipoma cases on the chest or back.
MRI is helpful in evaluating the extent of the tumour and the relationship of the tumour with adjacent bone and to the surrounding structures which may not be involved but possibly displaced structures confirming the benign nature.
Complete surgical excision remains the main stay of treatment.
Ethics statements
Patient consent for publication
Footnotes
Contributors The following authors were responsible for drafting of the text, sourcing and editing of clinical images, investigation results, drawing original diagrams and algorithms, and critical revision for important intellectual content: MT, SKM, TPT. The following authors gave final approval of the manuscript: SKM.
Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.
Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.