F-fluorodeoxy- glucose-positron emission tomography, CT and MRI are associated with a better assessment. The imaging find- ings associated with chest wall lesions are nonspecific

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Received 21.04.2020 Accepted 01.07.2020 Med Ultrason

2021, Vol. 23, No 3, 348-354

Corresponding author: Hyun Kyung Jung, MD Department of Radiology,

Inje University Haeundae Paik Hospital, 875 Haeun-daero, Haeundae-gu, Busan 48108, Republic of Korea Phone: 82-51-797-0363 Fax: 82-51-797-0373 E-mail: [email protected]

Introduction

Anterior chest wall lesions are found incidentally or may present as breast lumps. The categorization of chest wall lesions based on tissue origin is useful in the per- formance of differential diagnosis: fat, bone and soft tis- sue, including nerves, blood vessels, lymphatic vessels, muscles, cartilages and fibrous connective tissues. It is important to identify whether a lesion originates from the chest wall, as this can affect patient management [1].

Oliff et al [2] and Kuhlman et al [3] suggested the use of the radiologic approach for the evaluation of chest wall lesions; however, no protocols have been estab- lished so far. While patients undergo assessments using plain film radiography, US, computed tomography (CT), magnetic resonance imaging (MRI) and

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F-fluorodeoxy- glucose-positron emission tomography, CT and MRI are associated with a better assessment. The imaging find- ings associated with chest wall lesions are nonspecific

and have not been extensively described. Therefore, their evaluation may be challenging for radiologists. Although ultrasonography (US) is not considered the first imaging modality for the evaluation of chest wall lesions, such lesions may be initially encountered during breast US, especially if women complain of a palpable lump. In this pictorial essay, we illustrate the sonographic features of various anterior chest wall lesions that were detected on breast US.

Bilateral whole-breast US examinations in a supine position were performed using high-resolution US equip- ment with 7-12 MHz linear array transducers (iU22;

Philips Healthcare, Bothell, WA). Grayscale images were obtained routinely and additional images such as color Doppler images were obtained if necessary. The US find- ings were evaluated according to the American College of Radiology (ACR) Breast Imaging Reporting and Data System (BI-RADS) lexicon. When needed, US-guided core needle biopsy using a 14-gauge semiautomatic core biopsy needle (Stericut, TSK Laboratory, Tochigi, Japan) was performed.

Benign chest wall lesions Lipoma

In adults, a lipoma is the most commonly observed benign soft-tissue tumor, and does not require treatment until the tumor size is large. Lipoma is a sharply circum- scribed encapsulated mass composed of adipose tissue.

Abstract

Although anterior chest wall lesions rarely occur and the associated imaging findings are nonspecific, various disease pro- cesses can affect the chest wall. It is important for radiologists to understand the anatomic relationship between the chest wall and breast and differentiate the tumor origin. This pictorial essay presents the sonographic features of various anterior chest wall lesions that were detected on breast ultrasonography.

Keywords: chest wall; breast; ultrasonography

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On US, lipoma appears as a well-circumscribed hypere- choic/isoechoic mass compared to adjacent muscle, with fine internal echoes oriented parallel to the long axis of the tumor (fig 1) [4].

Hematoma

Soft-tissue hematoma may occur during direct com- pression trauma or after biopsy and surgery [5]. Clinical history and follow-up imaging studies help in the diag- nosis establishment, as hematomas regress over time [5].

On US, an acute hematoma is observed as a homogeneous echogenic mass with a fluid-fluid level, whereas chronic hematoma appears as a heterogeneous hypoechoic mass (fig 2) [6].

Abscess

Abscess formation in the chest wall is most common- ly observed in intravenous drug users and after trauma or surgery, and requires immediate surgical drainage [7].

Breast abscess is a complication of infectious mastitis.

On US, breast abscess presents as a variable shaped and sized multi-loculated mass, with a thick peripheral wall that has increased vascularity (fig 3) [8].

Injection granuloma related to mammoplasty

In the past, direct injection of liquid silicone or liquid paraffin into the breast was frequently performed for the augmentation of appearance [9]. Injection granulomas can occur after the implantation of various materials and these represent the final stage of inflammation and the wound-healing process. On US, injection granulomas present as multiple variable sized nodules with poste- rior acoustic shadowing (i.e. a snowstorm appearance) (fig 4) or a peripheral hyperechoic rim in the subcuta- neous fat layer, obscuring the underlying breast paren - chyma [9].

Fig 3. A 27-year-old woman with a palpable mass in the right upper chest wall. Transverse sonography of the right breast shows a hypoechoic mass with an irregular shape, microlobu- lated margin, and increased surrounding fat echogenicity (white arrows) (a). Color Doppler image shows increased surrounding vascularity (b). Excisional biopsy was performed and the mass was diagnosed as an abscess.

Fig 2. A 57-year-old woman with left breast pain that aggravat- ed when she lifted her left arm. She had slipped and fallen down 8 days previously. Transverse sonography of the left breast shows an indistinct heterogeneous echoic mass in the left upper chest wall (white arrows) (a), without vascularization (white arrows) (b). The mass disappeared on follow-up sonography after 1 year. This is suggestive of hematoma.

Fig 1. A 65-year-old woman with a palpable mass in the right breast. Mediolateral oblique mammography of the right breast shows a fatty mass in the right upper breast (white arrows) (a).

Transverse ultrasonography of the right breast shows an oval- shaped heterogeneous echoic mass with fine internal echoes in the right upper chest wall (white arrows) (b). These findings are suggestive of lipoma.

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Fat necrosis

Fat necrosis of the breast is a non-suppurative inflam- matory process and may occur after trauma, surgery, bi- opsy, breast reconstruction, fat graft, and radiotherapy.

It is detected incidentally or presents as a lump. On US, its appearance varies from a simple cyst to a hypoechoic or complex cystic and solid mass depending on the time - which is related to inflammation or fibrosis within the lesion (fig 5) [10].

Epidermal inclusion cyst

Epidermal inclusion cysts are commonly occurring cutaneous lesions that represent the proliferation of epi- dermal cells within a circumscribed dermal or subdermal space. Clinically, they present as firm, non-tender lumps and are typically located on the scalp, face, neck, trunk, and back. On US, they are seen as well-circumscribed pre- dominantly hypoechoic masses, with an ovoid or a spher- ical shape (fig 6) [11]. However, if they rupture, they may show variable imaging findings and can mimic infection.

Nodular fasciitis

Nodular fasciitis is a benign mesenchymal tumor characterized by the proliferation of fibroblasts and my-

Fig 5. A 55-year-old woman with a palpable mass in the left

chest wall; status post-left mastectomy and adjuvant chemo- therapy for breast cancer. Transverse sonography shows a complex cystic and solid mass in the left chest wall (white arrows) (a). Color Doppler image shows the absence of vascularity in the mass (b). US-guided core needle biopsy was performed and the diagnosis was fat necrosis with foreign body reaction.

Fig 6. A 56-year-old woman with a palpable mass in the right breast. Longitudinal sonography shows a complex cystic and solid mass in the subcutaneous layer (white arrows) (a). Color Doppler image shows the absence of vascularity in the mass (b).

Excisional biopsy was performed, and the mass was diagnosed as an epidermal cyst.

Fig 4. A 48-year-old woman with a palpable mass in her right chest wall for several months. She had undergone a direct injection of liquid silicone for cosmetic reasons as well as its subsequent removal. Mediolateral oblique mammography shows a fatty mass in the right upper breast (white arrows) and an enlarged lymph node in the right axilla (asterisks) (a). Transverse ultrasonography (US) shows focal fluid collection with two solid nodules (white arrows) (b). US shows diffuse acoustic shadowing by foreign body materials in the right axilla (c). US-guided fine needle aspiration of the fluid was performed and the aspiration was bloody only. The patient subsequently underwent excisional biopsy with right axillary dissection and the diagnosis was silicone granuloma.

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ofibroblasts in the subcutaneous tissues. The most com- monly observed sites are the upper extremities, with chest wall involvement noted in only 9% of all cases [12]. It commonly occurs in adults aged 20-50 years and pre- sents as a rapidly growing mass [12]. Surgical excision is the treatment of choice. On US, it is seen as an inho- mogeneous hypoechoic mass with a non-circumscribed

margin, an irregular shape, and an echogenic rim (fig 7) [13].

Intramuscular myxoma

Myxoma is a rare benign mesenchymal neoplasm that occurs most commonly in an intramuscular compart- ment, especially the thigh. Intramuscular myxoma rarely involves the chest wall [14]. On US, it presents as a well- defined anechoic mass with some internal echoes and a surrounding rim of fat (fig 8).

Myositis ossificans

Myositis ossificans is a benign heterotopic ossifica- tion of a soft-tissue mass that occurs in muscle and rarely in the chest wall. This lesion can be observed after local- ized trauma or neurologic injury [15]. The imaging find- ings are characterized by its stage of development. Calci- fications (osteogenesis) become apparent 3-8 weeks after

Fig 9. A 34-year-old lactating woman with a hard mass in her right chest wall. She had noticed the mass three years before but had not undergone evaluation. The mass had been growing recently. Longitudinal (a) and anti-radial sonography (b) of the right breast shows a hypoechoic mass with internal dense calcification in the right chest wall (white arrows) apart from the adjacent lactating breast (asterisks). Color Doppler image shows peripheral vascularity in the mass (c). US-guided fine needle aspiration was performed and mature fat cell clusters admixed with inflammatory cells were seen. Excisional biopsy was performed, and benign osseous tumor with suspicions of heterotopic ossification was diagnosed.

Fig 8. A 59-year-old woman underwent screening breast ultra- sonography (US). Transverse US of the right breast shows a hypoechoic mass with an oval shape and indistinct margin in the right chest wall (white arrows) (a). Color Doppler image shows indefinite mass vascularity (b). Excisional biopsy diagnosed an intramuscular cellular myxoma.

Fig 7. A 47-year-old woman with a palpable mass in the left breast. Transverse sonography of the left breast shows a hypoechoic mass with an indistinct margin and irregular shape in the left upper chest wall (white arrows) (a). Longitudinal sonography shows that the mass was connected with the skin (white arrow) (b) and has no vascularization (c). Excisional biopsy diagnosed a nodular fasciitis.

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onset, starting peripherally and progressing centrally in a zonal pattern. They evolve from faint irregular floccular calcification to dense calcification and, ultimately, to la- mellar bone with well-defined cortex forms (fig 9) [15].

Malignant chest wall lesions Breast cancer recurrence

Modified radical mastectomy (MRM) is among the surgical treatments for breast cancer. The rate of local recurrence in the chest wall after MRM ranges between 5% and 10%. Chest wall invasion may occur either by direct extension of the tumor through the pectoral fascia and into the pectoral muscles or by indirect extension via interpectoral nodes [16]. Tarja et al [17] reported that the sensitivity of US in the detection of local recurrence is higher than that of a clinical examination. On US, while most recurrent cancers appear as a hypoechoic mass, they may occasionally manifest as a hyperechoic mass (fig 10) [17]. Accurate diagnosis may be achieved with US- guided fine needle aspiration even in superficially located lesions or small lesions [1].

Malignant phyllodes tumor

The Phyllodes tumor is a rare fibroepithelial tumor of the breast. It is typically a large, fast-growing mass, arising from the periductal stroma of the breast. Its oc- currence is most common between the ages of 40 and 60 years, before menopause onset. Although most phyllodes tumors are benign, some are malignant or borderline.

Wide local excision is usually the first choice of treat- ment. Imaging features are similar for benign and ma-

lignant phyllodes tumors but tumor diameter ≥3 cm is associated with a higher likelihood of malignancy devel- opment [18]. On US, it is usually a well-defined heteroge- neous echoic mass without acoustic attenuation (fig 11).

Fig 10. A 52-year-old woman with a hard mass at the sternal area; status post-mastectomy. Anti-radial ultrasonography (US) shows a hypoechoic mass with an oval shape and microlobu- lated margin (thick white arrow) in the chest wall near the previous operation site (thin white arrow) (a). Color Doppler image shows the absence of increased vascularity in the mass (b).

US-guided core needle biopsy showed recurrent invasive ductal carcinoma.

tectomy for a recurrent borderline phyllodes tumor. Transverse sonography shows a large heterogeneous echoic mass with an indistinct margin at the left mastectomy site (a). Color Doppler image shows increased vascularity in the mass (b). The patient underwent modified radical mastectomy and the mass was diagnosed as a malignant phyllodes tumor.

Fig 12. A 36-year-old woman with a palpable mass in the left chest wall and previous ultrasound (US)-guided fine needle aspiration showing a possible spindle cell tumor. Longitudinal US shows a hypoechoic mass with an indistinct margin and irregular shape in the left chest wall, extending into the inter- costal space (white arrows) (a). Color Doppler image shows increased vascularity in the mass (b). Excisional biopsy was performed in our hospital and biphasic-type synovial sarcoma was diagnosed.

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Synovial sarcoma

Synovial sarcoma is a malignant soft-tissue tumor of unknown histogenesis that most commonly occurs near the large joints of the extremities in young adults. Syno- vial sarcoma arising from the chest wall is extremely rare [19]. It is clinically and morphologically a well-defined and slowly enlarging soft-tissue mass. The imaging find- ings associated with this tumor type are nonspecific, showing a heterogeneous and predominantly hypoechoic mass (fig 12).

Malignant fibrous histiocytoma

Malignant fibrous histiocytoma (MFH) is the most commonly observed soft-tissue sarcoma in adults, which has more recently been classified as undifferentiated pleomorphic sarcoma. It shows an aggressive biologi- cal behavior and offers poor prognoses and rarely occurs in the chest wall. There are several histologic subtypes, including the storiform-pleomorphic, myxoid, inflamma- tory, giant cell, and angiomatoid forms [19]. While the US findings associated with this tumor type are not well- known, one case of MFH appearing as a well-defined in- homogeneous low-echoic mass on US has been reported (fig 13) [20].

Conclusion

Although anterior chest wall lesions are uncommon and the imaging findings are nonspecific, various chest wall lesions may be detected on breast US. US can be used as an initial imaging modality for the evaluation of palpable chest wall lesions. It is important for radiolo- gists to understand the anatomic relationship between the chest wall and breast and the imaging findings associated with these disease entities for the appropriate manage- ment of chest wall lesions.

Fig 13. A 64-year-old woman with a palpable mass in the right breast for 3 months. Mediolateral oblique mammography of the right breast shows a high-density mass in the right axilla (white arrows) (a). Transverse sonography shows a large heterogeneous hypoechoic mass in the right chest wall (b). Color Doppler image shows increased vascularity in the mass (c). Excisional biopsy was performed, and the mass was diagnosed as a malignant fibrous histiocytoma.

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