Practical approach to ultrasound of soft tissue tumors and the added value of MRI: how I do it

Griffith, James Francis

doi:10.15557/jou.2023.0036

Figures & Tables

63-year-old male with enlarging thigh mass for five months. Transverse A. greyscale and B. color Doppler ultrasound show large moderately hyperemic mass (arrows) partially encasing the femoral (F) cortex. The large size, rapid growth, and moderate hyperemia make sarcoma most likely. No necrosis is evident. C. Axial proton-density weighted image shows that the tumor contacts, but does not infiltrate, the femoral cortex. The femoral neurovascular bundle (NVB) is also not infiltrated (arrowhead). T1-weighed fat-saturated post-contrast D. axial and E. sagittal images show that the central tumor area (*) is non-enhancing, compatible with necrosis. The necrosis cannot be appreciated on ultrasound A., B. Percutaneous biopsy of the tumor margins revealed a pleomorphic rhabdomyosarcoma

56-year-old female with discomfort and swelling in the infrascapular region. A. Clinical photograph shows site of swelling (arrow) marked by the patient prior to US examination. B. Transverse US shows a large mass with alternating hypoechoic bands (which are compatible with fibrous tissue) and hyperechoic bands (which are compatible with fatty tissue) at the inferior tip of the scapula (S). The mass was mildly compressible. No tumor vascularity was present on color Doppler imaging (not shown). This fibrolipomatous-type mass (arrowheads) is consistent with elastofibroma dorsi

4-year-old female with mass, deep to colored birthmark on dorsal aspect of trunk, enlarging over the past two years A. Clinical photograph shows the site of mass (arrow). Transverse B. greyscale and C. color Doppler US shows a medium-sized moderately hyperemic vascular anomaly involving the skin and subcutaneous tissues (arrowheads), most likely either venocapillary vascular malformation or hemangioma. No deep extension present. Follow-up US will be performed in two years to assess for further commensurate growth (favoring vascular malformation) or involution (favoring hemangioma)

75-year-old male with painful abdominal wall lump just cephalad to umbilicus. Transverse A. greyscale and B. color Doppler US show a medium-sized (15 mm long × 7 mm deep) hernia of the linea alba (arrow). The incarcerated hernia contains pre-peritoneal fat, some vascular channels, and no bowel. The linea alba fascial defect (arrowheads) measured 9 mm wide. Surgical reduction and repair were performed

44-year-old male with back lump clinically suggestive of lipoma. A., B. Transverse US shows a well-defined, oval-shaped, mildly compressible, mass (open arrow) with thin linear internal striations paralleling long axis of tumor. There was no demonstrable internal vascularity. The appearances are compatible with a subcutaneous lipoma. In this instance, as the tumor lies close to the investing fascia, the tumor margins (arrow) should be checked to confirm that the tumor is superficial to, rather than just deep to, the investing fascia (arrowheads). Subfascial lipomas have a higher risk of malignancy and, therefore, tend to be monitored and treated more actively than subcutaneous lipomas. An atypical lipoma would show features that look for the most part like a lipoma, though it has areas where the fine linear striations may not be readily apparent, and may have areas of calcification or areas of hyperemia

62-year-old female with slow-growing radial-sided wrist mass for two years. A. Longitudinal, B. transverse greyscale and C. longitudinal color Doppler US show a soft tissue mass (arrowheads) surrounding the 1st extensor compartment tendons (*), compatible with giant cell tumor of tendon sheath (GCTTS). Dynamic ultrasound can help to exclude intratendinous extension. GCTTS was confirmed on surgical excision

47-year-old female with slow-growing distal thigh mass for two years. Longitudinal A. greyscale and B. color Doppler US show a large well-encapsulated mildly hyperemic tumor (arrow) located between the investing fascia and the sartorius muscle (*). The overall appearance favored sarcoma. C. US image obtained during percutaneous biopsy shows sampling from the immediate subcapsular area of tumor (arrowheads). Histology was compatible with synovial sarcoma. D. T2-weighted fat-suppressed coronal MR image shows tumor (arrow) located proximal to medial femoral condyle (C) displacing the sartorius muscle deeply. Wide excision was performed with a 2 mm rim of muscle. No muscle invasion was present

41-year-old male with multiple, occasionally painful, subcutaneous lumps in the abdominal and thigh regions. A., B. Longitudinal US shows three variably-sized small echogenic masses (arrows) consistent with multiple subcutaneous lipomas (Dercum disease). Overall, there were more than twenty such lipomas present. When multiple lipomas exist, such as in this case, the lipomas tend to be more rounded, more echogenic, and have less pronounced internal striation and encapsulation than solitary lipomas

52-year-old male with a three-year history of slow-glowing medial ankle mass. Longitudinal A. greyscale and B. color Doppler US show a medium-sized nerve sheath tumor (NST) (*) arising concentrically from the tibial nerve (arrowheads). No tumoral vascularity was evident. Only 50% of NSTs have discernable neural continuity on US. Neural continuity may not be seen when NSTs arise from very small peripheral nerves

76-year-old female with a self-palpated nodular calf swelling slowly enlarging for one year. A. Longitudinal and B. transverse color Doppler US show a lobulated hypoechoic medium-sized (1.6 mm long × 0.8 mm deep × 3.0 cm wide) subcutaneous mass (*), in contact with, but not extending through, the investing fascia (arrowheads). C. Color Doppler US shows no demonstrable tumor vascularity. Either a solitary fibrous tumor or, less likely, plexiform neurofibroma, or a conglomerate of thrombosed varicose veins were considered the most likely diagnoses. Three months later, excisional biopsy was performed. Histology revealed myxoid dermatofibrosarcoma protuberans. Although the tumor margins were clear, wide local excision of the surgical bed was performed four months later. Three years later, the patient is well, with no evidence of recurrence

72-year-old male with painless lump in the apical pulp space of the index finger, which was slowly enlarging for one year. A. Clinical photograph shows the mass (arrow). Longitudinal B, C. greyscale and D. color Doppler US show a well-defined medium-sized mass (arrowheads) in the apical pulp space. The mass extends to, but does not definitely involve, the distal interphalangeal joint (DIPJ) (*). The mass seems to extend into a small cortical defect (open arrow) of the distal phalanx. No tumoral vascularity was evident. Overall, in view of possible intracortical extension, nerve sheath tumor was considered more likely than giant cell tumor tendon sheath (GCTTS) or glomus tumor. MRI and US-guided biopsy were recommended. MRI will help clarify the extent of the mass and possibility yield more information on the nature of the mass, such as hemosiderin deposition in GCTTS. Biopsy will help confirm the nature of the mass, which will help surgical planning

Schematic diagram showing the approach for percutaneous needle biopsy. The co-axial tip is placed just deep to the capsule, enabling it to be more easily directed to target different tumor areas. For suspected STS, samples should be preferentially obtained from area immediately deep to the capsule as well as any vascular areas rather than the central areas, which tend to be more necrotic

Elastography score based on color map ranging from score 1 (soft) to score 4 (hard)

57-year-old man with known subcutaneous recurrence of high-grade sarcoma (arrow). Shear wave elastography (SWE) shows that the known sarcoma recurrence is nearly entirely blue i.e. comprising hard tissue. Mean SWE modulus was 18.8 kPa. SWE ratio with subcutaneous fat (dashed circle) was 1.49. Elastography measures are not useful at differentiating benign soft tissue masses from sarcoma. Both these SWE modulus and ratio values can be observed in benign tumors, such as epidermoid cysts

Perfusion pattern types seen on CEUS. P1 (no enhancement) is characteristic of benign tumors. P2, P3, and P4 are non-discriminatory. P5 or P6 (marked enhancement) are more common in malignant tumors

63-year-old male following resection of well-differentiated liposarcoma posterior aspect thigh. T1-weighted (T1W) axial MR images thigh A. nine months post-operation shows severe semitendinosus muscle atrophy (*), increased intermuscular fat (arrowhead) between semimembranosus (Sm) and long head biceps femoris B. muscles as well a fatty mass (volume 1.6 ml) (open arrow) posterior to sciatic nerve (arrow). B. Fourteen months post-operation, the fatty mass posterior to sciatic nerve had increased by 143% (volume 3.9 ml). C. Nineteen months post-operation, the fatty mass posterior to sciatic nerve had further increased by another 130% (volume 9 ml), compatible with liposarcoma recurrence. MRI is generally better than US for post-operative surveillance. Volume, rather than linear, measurements provide a more ready appreciation of changing tumor size. In this case, volume measurements were made by formulaic estimation (length × width × depth × 0.52) rather than tumor segmentation

Schematic representation of NVB involvement. The NVB is resectable when it is A. not in contact with or B. just contacts the tumor margin. C. When the NVB is partially encased by tumor it is still usually resectable. D. When the NVB is completely encased by tumor, it is non-resectable, though exceptions may occur in some well-differentiated liposarcomas (Fig. 20)

55-year-old female with biopsy-proven undifferentiated pleomorphic sarcoma of thigh. A. T2-weighted fat-suppressed (T2W FS) axial MR image thigh shows a large soft tissue tumor in the anterior compartment contacting the cortex of the femoral shaft (*). It was uncertain whether the femoral vessels (open arrow) were involved by tumor. B. T2W FS axial MR image thigh with surface coil (inset) shows clearer delineation of femoral vessels (open arrow), which do not seem to be infiltrated by tumor. C. Proton-density-weighted (PDW) axial MR image with microscopy coil (inset) shows femoral artery and vein (open arrow) unequivocally not involved by tumor. Use of different MR techniques enables more confident assessment of NVB infiltration

72-year-old male with biopsy-proven malignant fibrous histiocytoma of the popliteal fossa. A. PDW axial MR image with standard coil shows possible partial encasement of the popliteal artery (open arrow) by tumor (T). A, B. PDW axial MR image with microscopy coil (inset) shows the popliteal artery (open arrow), vein, and tibial nerve to be clearly separated from tumor (T)

78-year-old male with well-differentiated liposarcoma of the thigh. Axial T1W MR image shows A. a high division of the sciatic nerve into the tibial and peroneal nerves (arrows) and B. a large intermuscular liposarcoma (open arrow), between the adductor and hamstring muscle groups, encasing the tibial and peroneal nerves (arrows). C.-E. Clinical photographs of surgically exposed tumor (open arrow) showing the invaginated tibial nerve (arrows) which, for the most part, easily freed from the tumor pseudocapsule. As the tibial nerve was focally tethered in the mid-portion of the tumor, the epineurium in this area was resected. The exposed nerve fibers were not visibly infiltrated by tumor. E. Preserved tibial and peroneal nerves (arrows) after complete tumor resection. Histologically, the tethered small segment of the tibial nerve had epineurial tumor involvement. Three years after resection, the patient has no local recurrence

Features which favor malignancy in soft tissue tumors

1.	Progressive growth of tumor clinically (particularly if growth is rapid and patient has or had known primary tumor)
2.	Middle-aged or elderly patient
3.	Medium to large-sized tumor (>2 cm if superficial), (>3 cm if deep)
4.	Moderate to severe tumor hyperemia (if superficial) Mild to moderate tumor hyperemia (if deep)
5.	More rounded, rather than elongated, tumor shape
6.	Chaotic, rather than organized, tumoral vascular pattern
7.	Lack of similarity with the known US appearances of particular benign soft tissue masses

Based on data compiled from the references Hung et al_4 and Griffith et al_5 The studies employed identical methodology to investigate the accuracy of US when experienced examiners were confident about the US diagnosis of (both neoplastic and non-neoplastic) superficial and deep soft tissue masses_ Masses without histology were followed up clinically_ Of 1,402 soft tissue masses studied, the examiner was confident about the type of mass in 71–75% of cases_ Compared to histology, this confident diagnosis was correct in 95-96% of cases_ Of the nine incorrect diagnoses, eight were benign tumors found to be another type of benign tumor_ The ninth case was considered to be a benign tumor (calcified granuloma) on US, though it was found to be malignant histologically (calcified metastasis)_ Therefore, for patients with a confident US diagnosis, malignancy was overlooked in only <0_1% of soft tissue masses overall and in <0_3% in those with histology

	Superficial masses	Deep masses
Number of masses studied (n = 1402)	823	579
‘Confident diagnosis’ regarding nature of mass	585 (71%)	436 (75%)
Number of masses with subsequent histology	219/823 (27%)	134/579 (34%)
‘Confident diagnosis’ regarding nature of mass in masses with histology	132/219 (60%)	67/134 (57%)
Correct ‘confident diagnosis’ compared to histology	126/132 (95%)	64/67 (96%)
Incorrect confident diagnosis for superficial masses (n = 6): Glomus tumor considered to be nerve sheath tumor Dermoid cyst considered to be infected collection Vascular leiomyoma considered to be vascular anomaly Vascular anomaly considered to be lipoma Neurofibroma considered to be epidermoid cyst Calcified metastatic deposit considered to be calcified granuloma
Incorrect confident diagnosis for deep masses (n = 3): Giant cell tumor of tendon sheath (GCTTS) considered to be ganglion Vascular malformation considered to be intra-fascial lipoma Organized inflammatory mass considered to be lipoma

Suggested further work-up of soft tissue tumors following US assessment in situations where (a) one is confident regarding ultrasound diagnosis, or when the ultrasound diagnosis is not certain, though there is (b) no evidence of malignancy or (c) possibility of malignancy

Confident regarding diagnosis

Indeterminate mass with no evidence of malignancy

Indeterminate mass with possibility of malignancys

Provide definitive diagnosis.

If benign, no need for additional investigation in most instances.

If considered malignant, proceed to: percutaneous biopsy ± MRI.

List three most likely diagnoses ± comment that tumor is much more likely to be benign rather than malignant.

Proceed to either:

percutaneous biopsy
excisional biopsy
MRI examination
follow-up ultrasound

Proceed to:

percutaneous biopsy
± MRI examination

Some soft tissue masses (both neoplastic and non-neoplastic) which tend to have a more distinctive US appearance_ The perceived frequency with which each of these specific tumors can be characterized based on US assessment alone is also provided_

Superficial		Deep
Neoplastic	Non-neoplastic	Neoplastic	Non-neoplastic
Lipoma and variants^A	Epidermoid cyst^B	Lipoma and variants^A	Elastofibroma dorsi^A
Vascular anatomy^B	Inflammatory mass^A	GCTTS^{^B}	Ganglion^{^A}
Nerve sheath tumors^{^C}	Foreign body granuloma^B	Plantar or palmar fibroma^A	Bakers’ cyst^A
Pilomatrixoma^C	Calcified or injection granuloma^A	Fibromatosis (desmoid tumor)^B	Hernia^A
Lymph node^A	Fat necrosis^B	Myxoma^C	Gouty tophus^B
Leiomyoma^C	Rheumatoid nodule^B	Sarcoma^B	Hematoma^B
Subcutaneous lymphoma^C	Panniculitis-like mass^C	Subcutaneous lymphoma^C	Varix, pseudoaneurysm, aneurysm^A
	Lymphocele^B
	Lipohypertrophy/lipomatosis^A		Myositis ossificans^B
	Encysted fluid spermatic cord/canal of Nuck^B		Muscle hypertrophy^A
			Abscess or collection^A
	Intravascular papillary epithelial		Morton’s neuroma^B
	hypertrophy^C		Bursitis^A
	Organizing hematoma^B		Endometriosis^C
	Tumoral calcinosis^B		Xanthoma^C
	Accessory breast issue^A

Potential advantages of MRI over US in the assessment of soft tissue masses

More global, encompassing assessment
Anatomical road map to excision
Appreciation of extent of large ill-defined tumor, such as vascular malformation
Delineation of medium or large deep-seated mass
Delineation of large mass in anatomically complex areas such as the wrist or mid-foot
Delineation of mass in any area where transducer access is limited
Assessment of peritumoral and muscle edema
Delineation of neurovascular infiltration
Delineation of bone and joint involvement
Tumor tissue composition
Tumor characterization occasionally
Monitoring chemotherapy response (functional imaging)
Surveillance for STS tumor recurrence (± functional imaging)

Practical approach to ultrasound of soft tissue tumors and the added value of MRI: how I do it

Figures & Tables

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Features which favor malignancy in soft tissue tumors

Suggested further work-up of soft tissue tumors following US assessment in situations where (a) one is confident regarding ultrasound diagnosis, or when the ultrasound diagnosis is not certain, though there is (b) no evidence of malignancy or (c) possibility of malignancy

Some soft tissue masses (both neoplastic and non-neoplastic) which tend to have a more distinctive US appearance_ The perceived frequency with which each of these specific tumors can be characterized based on US assessment alone is also provided_

Potential advantages of MRI over US in the assessment of soft tissue masses

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