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Posterior Chest Wall

Clinical Summary

A 59-year-old woman presents with a newly identified back mass. She denies any tenderness or recent trauma. A firm, immobile mass is palpated in the deep soft tissue at the inferior angle of the left scapula. ​O​verlying skin changes are absent. Intraoperatively, the mass is noted to be firm and indistinct, extending from the scapula to the underlying rib. Gross examination of the mass reveals a poorly demarcated 10 cm area of firmness that has a variegated grey and yellow color. A Verhoeff–Van Gieson stain highlights microscopic fibers.  

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Master List of Diagnoses 

Amyloidoma
Desmoid-type fibromatosis
Elastofibroma
Nuchal-type/Gardner fibroma
Spindle cell lipoma 

Archive Case and Diagnosis

This case first appeared as Performance Improvement Program in Surgical Pathology (PIP) 2022, Case 06, and is elastofibroma of the posterior chest wall. The information provided in this case was accurate and correct at the time of publication in 2022. Any changes in terminology since the time of publication may not be reflected in this case.  

Criteria for Diagnosis and Comments

Microscopically, the tumor comprises short, bland spindle cells in a smooth collagenous matrix infiltrating through mature adipose tissue. Scattered brightly eosinophilic fibers of varying sizes are noted, some with prominent serrated borders. These elastic fibers are key to the diagnosis of elastofibroma.

Elastofibroma was originally described by Järvi and Saxén in 1961 as a lesion of the subscapular region consisting of a mixture of collagen, adipocytes, and an abundance of abnormal-appearing elastic fibers. Although most cases arise in the deep soft tissue at the inferior aspect of the scapula, it can arise in other locations, such as in the soft tissue near the olecranon. There is a strong female predominance, and the peak incidence is in the 7th to 8th decades, although rare cases are identified in children. A familial predisposition is recognized to play a role in some cases. In both imaging and autopsy case series that have looked at tissue from the inferior aspect of the scapula, elastofibromas or early elastofibroma-like changes are identified in a significant proportion of asymptomatic individuals. Excision is curative, even if incomplete.

The characteristic elastic fibers of elastofibroma are seen on H&E-stained sections as deeply eosinophilic glassy fibers, but they can be subtle and difficult to distinguish from collagen. Compared to normal elastic fibers, they are thick, can form globules that may string together forming a beaded appearance, and frequently have irregular serrations. Histochemical stains that highlight elastic fibers, such as the Verhoeff–Van Gieson​ (VVG)​ stain, will help to identify them and highlight their morphology. Fibroblasts within the lesion can be positive for CD34 by immunohistochemistry.

The etiology of elastofibroma is not well established. The fact that they arise in areas of high mechanical stress and​ may be bilateral​ has led many to suggest they are reactive in nature. However, both non-random X chromosome gene inactivation and recurrent chromosomal changes have been identified, suggesting a clonal nature.

Amyloidoma histologically shows a well-circumscribed localized deposition of amyloid forming a mass with the potential to mimic an elastofibroma. It is often associated with T lymphocytes, plasma cells, and granulomatous reaction with calcification and ossification. Some patients have an underlying factor predisposing them to develop amyloid deposition, such as a chronic inflammatory condition. The lack of elastic fibers and positive staining with Congo red will reliably separate this from elastofibroma.

Desmoid-type fibromatosis is a benign tumor with infiltrative borders and a propensity for local recurrence. Desmoid-type fibromatosis occurring in patients with familial adenomatous polyposis is known as Gardner syndrome. Histologically, desmoid-type fibromatosis is generally more cellular and has a more well-organized appearance than elastofibroma. Long fascicles of spindle cells with intervening vessels that have a stretched-out appearance and mild surrounding edema are typical. The spindle cells have a myofibroblastic appearance with slightly basophilic cytoplasm and inconspicuous nucleoli. Some cases contain keloid-type collagen that may mimic elastic fibers but are negative with an elastic stain. Nuclear beta-catenin staining is seen in most cases, and abnormal elastic fibers are absent. CTNNB1 or APC mutations may be seen.  

Nuchal-type and Gardner fibromas are morphologically similar lesions with dense collagen and scattered bland-appearing fibroblasts. Artifactual cracking of the collagen is sometimes appreciated in these lesions. Typically, nuchal-type fibromas are seen in middle-aged adults in the posterior lower neck or upper back, while Gardner fibromas are found in children in the back or paraspinal region. Although they usually arise superficial to the fascia, they may infiltrate the underlying muscle. Both of these lesions lack the abnormal elastic fibers of elastofibroma, and some cases of Gardner fibroma will show nuclear positivity with a beta-catenin immunohistochemical stain.

Spindle cell lipomas comprise a mixture of bland spindle cells and adipocytes set in a collagenous and myxoid background. They most often present as subcutaneous nodules in the back, shoulder, or posterior neck. There is a strong male predilection, with peak incidence in the 5th to 7th decades. The collagen fibers of spindle cell lipoma are described as having a “ropey” appearance. Spindle cell lipomas lack the abnormal elastic fibers of elastofibroma. By immunohistochemical staining, they are positive for CD34 and show loss of nuclear Rb1 staining, the latter a result of a monoallelic 13q14 deletion (the location of the RB1 gene), which may help in the distinction. 

Educational Questions

  1. Which of the following molecular alterations are seen in spindle cell lipomas? 

    1. Amplifications of MDM2 (12q15) 

    2. Gene fusions involving HMGA2 (12q14.3) 

    3. Gene fusions involving NAB2 (12q13.3) and STAT6 (12q13.3) 

    4. Monoallelic deletions of RB1 (13q14.2)

    5. Point mutations in codon 41 or 45 of CTNNB1 (3p22.1) 

  2. Which of the following stains is the most useful to confirm a diagnosis of elastofibroma?

    1. Beta-catenin 

    2. CD34 

    3. PAS 

    4. RB1 

    5. Verhoeff–Van Gieson 

  3. Which of the following features is required for diagnosis of elastofibroma? 

    1. Abundant normal-appearing elastic fibers 

    2. Cytogenetic abnormalities 

    3. Elastic fibers with abnormal morphology 

    4. History of repetitive motion

    5. Tumor location at the inferior angle of the scapula 

View Answer Key

References

  1. Brandser EA, Goree JC, El-Khoury GY. Elastofibroma dorsi: prevalence in an elderly patient population as revealed by CT. AJR Am J Roentgenol. 1998;171(4):977-980.
  2. Hernández JL, Rodríguez-Parets JO, Valero JM, et al. High-resolution genome-wide analysis of chromosomal alterations in elastofibroma. Virchows Arch. 2010;456(6):681-687.
  3. Goldblum JR, Folpe AL, Weiss SW, eds. Enzinger and Weiss's Soft Tissue Tumors. 7th Edition. Elsevier. 2020;235-237.
  4. Hisaoka M, Hashimoto H. Elastofibroma: clonal fibrous proliferation with predominant CD34-positive cells. Virchows Arch. 2006;448(2):195-199.
  5. Järvi OH, Länsimies PH. Subclinical elastofibromas in the scapular region in an autopsy series. Acta Pathol Microbiol Scand A. 1975;83(1):87–108.
  6. Järvi O, Saxén E. Elastofibroma dorsi. Acta Pathol Microbiol Scand Suppl. 1961;51(Suppl 144):83–84.
  7. Nagamine N, Nohara Y, Ito E. Elastofibroma in Okinawa. A clinicopathologic study of 170 cases. Cancer. 1982;50(9):1794-1805. 

Answer Key

  1. Which of the following molecular alterations are seen in spindle cell lipomas? 
    A. Amplifications of MDM2 (12q15) 
    B. Gene fusions involving HMGA2 (12q14.3) 
    C. Gene fusions involving NAB2 (12q13.3) and STAT6 (12q13.3) 
    D. Monoallelic deletions of RB1 (13q14.2)
    E. Point mutations in codon 41 or 45 of CTNNB1 (3p22.1) 
  2. Which of the following stains is the most useful to confirm a diagnosis of elastofibroma?
    A. Beta-catenin 
    B. CD34 
    C. PAS 
    D. RB1 
    E. Verhoeff–Van Gieson 
  3. Which of the following features is required for diagnosis of elastofibroma? 
    A. Abundant normal-appearing elastic fibers 
    B. Cytogenetic abnormalities 
    C. Elastic fibers with abnormal morphology 
    D. History of repetitive motion
    E. Tumor location at the inferior angle of the scapula 
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