None. Everyone, especially Dr. Mitchell for helping me find cases!

Sagittal T1

Coronal T1

Axial T1

Sagital T1, Axial T1+, Axial T2

Axial CT +, thorax

Axial T1

Within the muscle, not connected to a nerve or vessel Faint internal enhancement on T1+ (not shown) Axial T1 Axial T2

Review a systematic approach for work up of a soft tissue mass. Highlight key points of some of the more common entities.

Soft tissue arises from the mesenchyme. Which differentiates to: fat skeletal muscle peripheral nerves Blood vessels Fibrous tissue Figure 1: Soft tissue layers. <http://radiologykey.com/superficial-soft-tissues-masses/>

1. Adipocytic 2. Fibroblastic/myofibroblastic 3. Fibrohistiocytic 4. Smooth muscle 5. Pericystic (perivascular) 6. Skeletal Muscle 7. Vascular 8. Chondro-osseous 9. Uncertain differentiaion

Review a systematic approach for work up of a soft tissue mass. Highlight key points of some of the more common entities.

Characterization of these soft-tissue lesions remains problematic, despite advances in imaging. Let s go over an approach, while highlighting some of these lesions.

Chan WP. Magnetic resonance imaging of soft-tissue tumors of the extremities: A practical approach. World Journal of Radiology. 2013;5(12):455-459. doi:10.4329/wjr.v5.i12.455.

Chan WP. Magnetic resonance imaging of soft-tissue tumors of the extremities: A practical approach. World Journal of Radiology. 2013;5(12):455-459. doi:10.4329/wjr.v5.i12.455. Determinate Lesions imaging features allowing a diagnosis without biopsy Indeterminate Lesions one that must be biopsied to ensure an accurate diagnosis

Chhabra and Soldatos. Soft-Tissue Lesions: When Can We Exclude Sarcoma? American Journal of Roentgenology. 2012;199: 1345-1357. 10.2214/AJR.12.8719

Wu JS, Hochman MG. Soft-tissue tumors and tumorlike lesions: a systematic imaging approach. Radiology 2009; 253:297 316

1. Clinical History 2. Location 3. Does it arise from something? 4. What does the radiograph show? 5. Is it hyperintense on T1? 6. Is it hypointense on T2? 7. Is it hyperintense on T2?

Important information: Age (eg: liposarcomas are rare in children) Hx of trauma (hematoma, myositis ossificans) History of malignancy or familial syndromes (metastasis, radiation induced sarcoma, NF type 1) Mass characteristics (rapid growth, size fluctuation, mobile,etc).

1. Clinical History 2. Location 3. Does it arise from something? 4. What does the radiograph show? 5. Is it hyperintense on T1? 6. Is it hypointense on T2? 7. Is it hyperintense on T2?

Some masses occur in specific locations. You just have to know them. - Let s look at some!

Axial CT +, thorax

Subscapular mass deep to serratus anterior. 99% in subscapular region. 10-66% bilateral Mean age: 65-70 years. F > M Slow growth, no malignant degeneration CT imaging findings: Poorly defined, lenticular, heterogeneous soft tissue mass Linear low-attenuation streaks from internal fat Majority of lesion has attenuation similar to muscle

(distal fingers) Coronal T2 Coronal T1

Mesenchymal neoplasm of smooth muscle cells similar to glomus body cells Propensity to subungual region. Fingers and toes most common 99% benign, but often painful. MR imaging findings: Isointense to nail bed or muscle on T1 Hyperintense on T2

Case reports of other locations:

(Metatarsals) Coronal T1 Coronal T1 post gad Coronal T2

Painful, benign fibrosing process of plantar digital nerve between 3rd and 4th metatarsal heads. most common. F>M MR imaging findings: Hypo to Isointense on T1 Iso to Hyperintense on T2 Variable enhancement

Sagittal T1

Benign discrete nodule along plantar fascia. Ages 30-80 years M:F = 1:1 MR imaging findings: Isointense on T1 Hypo to isointense on T2

1. Clinical History 2. Location 3. Does it arise from something? 4. What does the radiograph show? 5. Is it hyperintense on T1? 6. Is it hypointense on T2? 7. Is it hyperintense on T2?

Only a few things arise from a nerve: PNSTs (schwannomas and neurofibromas) If fat, consider Neural fibrolipoma/fibrolipomatous hamartoma

Sagital T2, elbow

Neurofibromas Schwannoma Malignant Peripheral Nerve Sheath Tumors

Benign PNST with neoplastic tissue inseparable from normal nerve Localized NF: 90% of cases, primarily affect superficial cutaneous nerves, can affect larger deeper nerves Diffuse NF: Ill-defined plaque-like in the subcutaneous tissue Plexiform NF: Long segments of diffusely and irregularly enlarged nerves. Multilobulated. Pathgonomic for NF1.

Arises in 2nd to 3rd decade of life Low risk of malignant transformation (though higher risk with the deeper lesions). Painless, slowly growing nodule

Iso to mildly hyperintense (Hypointense also possible) on T1 Split-fat sign = peripheral rim of fat Hyperintense on T2 Variable heterogeneity Target sign = central low signal focus Fascicular sign = multiple small ring-like structures + enhancement, most prominent centrally

Coronal T1 Coronal T2 Coronal T1+

In contrast to schwanomas, neurofibromas incorporate many cell types in addition to Schwann cells May be impossible to differentiate from a neurofibroma from a schwanoma via imaging.

Encapsulated benign peripheral nerve sheath tumor typically located eccentrically on normal nerve Upper and lower extremity flexor surface nerves Well-defined, solitary fusiform mass Most common in 2nd to 5th decades of life Painless, slowly growing

Iso to hyperintense on T1 Split-fat sign = thin peripheral rim of fat May have subtle muscle atrophy distal to lesion Hyperintense on T2 Target sign = central low signal region Fascicular sign = multiple small ring-like structures Diffuse enhancement (often greater than neurofibroma) is typical.

Sagital T1, Axial T1+, Axial T2

Infiltrative, often invasive, fusiform mass > 5 cm Large to medium deep nerves (Sciatic nerve > brachial plexus, sacral plexus) Proximal extremities, retroperitoneum, posterior mediastinum Malignant spindle cell sarcoma of neural origin. 25-70% associated with NF1 10-20% radiation-induced 5-year survival rate: 23-44%

Heterogeneously hypo- to hyperintense on T1WI MR Heterogeneously hyperintense on fluidsensitive MR ± hemorrhagic fluid-fluid levels Intense heterogeneous enhancement Diffuse, peripheral or nodular patterns

Sagittal T2 and Axial T1.

Does it arrive from a vessel? Hemangioma would be the most common Other possibilities include lymphangiomas and angiosarcomas. If there is a Hx of trauma, consider a pseudoaneurysm.

Does it arrive from a tendon sheath? Most commonly would be a Giant Cell Tumor of the tendon sheath. Nonetheless, ganglia, lipomas and fibromas can all arise from tendon sheaths.

nodular tenosynovitis, tenosynovial giant cell tumor, Benign synovial proliferation within tendon sheath same pathologic entity as pigmented villonodular synovitis (PVNS)

85% in fingers. Hand > wrist > ankle/foot > knee > elbow > hip 30-50 years. M:F = 2:1 Local recurrence in 4-44% Radiographs: Nonspecific soft tissue fullness. Cortical erosion in 10-28%

Inhomogeneous low to intermediate signal intensity on T1 and T2 "bloom" on gradient-echo imaging Intense enhancement ± inhomogeneity

Axial T1, Axial T2 and Gradient Echo

1. Clinical History 2. Location 3. Does it arise from something? 4. What does the radiograph show? 5. Is it hyperintense on T1? 6. Is it hypointense on T2? 7. Is it hyperintense on T2?

They should be assessed for: distortion of tissue planes, radiolucent fat indolent or aggressive remodeling of the bone soft-tissue calcifications or ossification.

Heterotopic formation of bone and cartilage in soft tissue At the site of injured muscle (quads/arms most common). Classic appearance: Mature bone formation within soft tissues. Early stages can be confusing and non specific.

Myositis is misleading May also be found in fascia, tendons, & fat. "Heterotopic ossification" is more correct term

0-2 weeks: Soft tissue mass with indistinct surrounding soft tissue planes 3-4 weeks: Amorphous osteoid forms within mass; adjacent periosteal reaction may be seen 6-8 weeks: Sharper cortex begins to form about lacy central osseous mass 5-6 months: Mature bone formation

Axial T2, Radiograph and Sagittal CT

1. Clinical History 2. Location 3. Does it arise from something? 4. What does the radiograph show? 5. Is it hyperintense on T1? 6. Is it hypointense on T2? 7. Is it hyperintense on T2?

MRI is the most effective for tissue characterization. As usual, the signal intensity of T1 and T2 weighted images are compared to muscle

This isn t useful, too many lesions with these signal characteristics.

1. Clinical History 2. Location 3. Does it arise from something? 4. What does the radiograph show? 5. Is it hyperintense on T1? 6. Is it hypointense on T2? 7. Is it hyperintense on T2?

Consider this flow chart:

Benign adipocytic tumors Intermediate adipocytic tumors Malignant adipocytic tumors

Lipoma Lipomatosis Nerve Lipomatosis Lipoma Arborescens, Knee Lipoblastoma (pediatrics) Hibernoma Parosteal Lipoma

Benign Adipocytic tumors Same signal as fat Only thin septa (< 2mm) No nodules While calcification can occur, it should raise suspicion. Axial T1

Benign Adipocytic tumors Same signal as fat Disorganized and poorly circumscribed fat overgrowth Associated with various syndromes Axial T1

Benign Adipocytic tumors 78-96% in upper extremity (80% in median nerve distribution) Collection of enlarged cylindrical fascicles along course of nerve, like a coaxial cable Axial T1

Benign Adipocytic tumors Most common in suprapatellar recess of knee joint Frond-like or globular pattern of fat proliferating from synovial membrane Treat w/synovectomy Sagital T2

Benign Adipocytic tumors Rare, benign tumor of brown adipose tissue Needs biopsy, because imaging alone can t exclude non benign lipomatous lesions More complex then a lipoma, multiple septa and prominent vascularity Axial T1

Benign Adipocytic tumors Fatty lesion arising from bone surface Approximately 33% adjacent to femur Internal calcifications, septa, ossifications Adjacent bone shows osseous excrescence and bone cortex changes, such as thicknening

Atypical lipomatous tumor or Well-differentiated liposarcoma

Intermediate Adipocytic tumors or Intermediate, locally aggressive neoplasm predominantly composed of fat typically composed of > 75% fat with septa and variable nodularity Does not metastasize. 0% mortality for lesions in extremities 80% mortality for retroperitoneal lesions

Intermediate Adipocytic tumors or Axial T1

Liposarcoma

Malignant Adipocytic tumors Typically ages 40-60. In extremities or retroperitoneum. 5 types: Well-differentiated commonest, low grade, Myxoid - intermediate grade Round Cell/de-differentiated, high grade Pleomorphic, high grade Mixed

Malignant Adipocytic tumors Low grade lesions are almost entirely fat signal with thick septa, nodules +/- evidence of local invasion. The higher grade lesions are often devoid of macroscopic fat and have appearances similar to other sarcomas.

Malignant Adipocytic tumors Axial CT Sagital T1

Axial PD FatSat

Axial PD Fatsat Axial T1 Axial T1 FatSat Axial T1 FatSat +

1. Clinical History 2. Location 3. Does it arise from something? 4. What does the radiograph show? 5. Is it hyperintense on T1? 6. Is it hypointense on T2? 7. Is it hyperintense on T2?

Divide the differential into 3 categories: 1. Fibrosis 2. Hemosiderin 3. Calcification

Can still be hyperintense on T2!

Benign neoplasm originating from smooth muscle Punctate, plaque-like, or "popcorn" calcifications Iso to slightly hyperintense T1 Hypo to hyperintense on T2. Excision, rare recurrence Subcutaneous lesions are small <2cm Deep lesions are larger

Axial T1 Axial T2 Axial T1+

Malignant fibroblastic/myofibroblastic neoplasm Often in deep soft tissues of extremities Commonly 3-8 cm at presentation Variable appearance depending on cellular content. Thus heterogenous appearance that can be low to high signal intensity on T1 and T2 Estimated 39-54% 5-year survival Metastases in 9-63%

Axial T2 Axial T1+

1. Clinical History 2. Location 3. Does it arise from something? 4. What does the radiograph show? 5. Is it hyperintense on T1? 6. Is it hypointense on T2? 7. Is it hyperintense on T2?

Look at the enhancement pattern. Is it rim enhancing, or demonstrate internal enhancing components?

Axial T1 Axial T2 Rare benign type of soft tissue myxoma 40 to 70 years. F>M homogeneous low T1, high T2, mild internal enhancement Simple excision is curative

Fibroblastic soft tissue sarcoma involving elderly patients. 60-80 years. Low grade: homogeneous low T1, high T2, mild internal enhancement High Grade: heterogeneous intermediate T1, high T2, intense enhancement ± hemorrhage, necrosis High local recurrence rate (38-79%). Even with lowgrade tumors

Malignant soft tissue tumor of uncertain differentiation. 95% in the extremities, Often in the knees. 15-40 years of age Does not arise from synovium. 5-year survival rate: 27-76% Metastases in up to 41%

Imaging findings are not pathognomonic. Iso to slightly hyperintense on T1 and heterogeneous Mostly hyperintense on T2. Markedly heterogeneous. Calcification in 1/3 but extent variable "Triple" sign = multiple signal intensities due to hemorrhage, necrosis, solid tissue, and calcification "Bowl of grapes" sign = multiloculated appearance of mass with internal septa Fluid Fluid levels = Intra-tumoral hemorrhage Enhancement is usually prominent and can be diffuse, heterogeneous or peripheral.

Due to variable appearance any soft tissue mass near a joint, especially containing calcification, should not be dismissed as being benign.

Coronal T1 Coronal T2 Fatsat

Axial PD Axial T1+

Sagittal and Axial T2 Fluid Fluid levels and Triple Sign Coronal T2 Bowl of Grapes sign

1. Clinical History 2. Location 3. Does it arise from something? 4. What does the radiograph show? 5. Is it hyperintense on T1? 6. Is it hypointense on T2? 7. Is it hyperintense on T2?

While a systematic approach can narrow a differential, it is not comprehensive. If a lesion can not be confidently diagnosed then it is an intermediate lesion.

According to WHO soft tissue masses that do not demonstrate tumor-specific features on MR images should be considered indeterminate and biopsy should always be obtained to exclude malignancy.

1. Clinical History 2. Location 3. Does it arise from something? 4. What does the radiograph show? 5. Is it hyperintense on T1? 6. Is it hypointense on T2? 7. Is it hyperintense on T2?

Sagittal T1

Coronal T1

Axial T1

Sagital T1, Axial T1+, Axial T2

Axial CT +, thorax

Axial T1

Axial T1 or

Within the muscle, not connected to a nerve or vessel Faint internal enhancement on T1+ (not shown) Axial T1 Axial T2

Axial T1 Axial T2

1. Clinical History 2. Location 3. Does it arise from something? 4. What does the radiograph show? 5. Is it hyperintense on T1? 6. Is it hypointense on T2? 7. Is it hyperintense on T2?

Question 5 quiz: Walker, C. Elastofibroma https://app.statdx.com/document/elastofibroma/7b872a86-912f-455c-99c5-5be315bd63a2?searchterm=elastofibroma Slide 62: Roberts, C. Glomus Tumor https://app.statdx.com/document/glomustumor/82f6482a-26a9-43eb-8d97-98fdcc9330cd Slide 65: Blankenbaker, D. Morton Neuroma https://app.statdx.com/document/morton-neuroma/0ffb1062-4d8c-442c-bbdbfdcf0d719402 Slide 67: Unknown author. Plantar Fibroma http://www.bonetumor.org/plantarfibroma-foot-and-ankle?page=2 Slide 88: Roberts, C. Schwannoma https://app.statdx.com/document/schwannoma/be99bba5-0506-4125-9f26-54792a0b69f9 Slide 91: Chen, K., Zhou, M., Yang, H., Qian, Z., Wang, G., Wu, G.... Sun, Z. (2013). Pre-operative embolization facilitating a posterior approach for the surgical resection of giant sacral neurogenic tumors. Oncology Letters, 6, 251-255. http://dx.doi.org/10.3892/ol.2013.1328 Slide 95: Roberts, C. Giant Cell Tumor of the Tendon Sheath https://my.statdx.com/document/giant-cell-tumor-tendon-sheath/55c34321-d2b1-4da7-b5cc-5a2eba5908ab Slide 97: Wan, J., Magarelli, N., Peh, W. et al. Giant Cell Tumor of the Tendon Sheath Radiol med (2010) 115: 141. doi:10.1007/s11547-010-0515-2

Slide 101: Roberts, C. Hemangioma https://my.statdx.com/document/hemangiomasoft-tissue/2dce9ded-ed4f-481f-86e3-8c0f2f1d753c Slide 103 and 107: Banaster, M. Myositis Ossificans https://my.statdx.com/document/myositis-ossificans-heterotopic-os-/d041548b-0dc9-4042-b056-3ebea0c7c3d1 Slide 118: Roberts, C, Lipoma https://my.statdx.com/document/lipoma-softtissue/24a2442e-f539-483e-af31-33db5c3f8a66 Slide 119: Roberts, C. Lipomatosis https://my.statdx.com/document/lipomatosis/a7ef3528-5c36-4595-a693-68966edac95c Slide 120: Roberts C. Lipomatosis of a nerve https://my.statdx.com/document/lipomatosis-nerve/d217207e-8933-4997-b884- b759d6caf025 Slide 121: Weerakkody et al. Lipoma Arborescens http://radiopaedia.org/articles/lipoma-arborescens-1 Slide 122: Goel, A at al. Hibernoma http://radiopaedia.org/articles/hibernoma Slide 123: Lawson, A. Parosteal lipoma http://radiopaedia.org/cases/parosteal-lipoma Slide 126: Nicoletti, D. Atypical lipomatous tumor http://radiopaedia.org/cases/atypical-lipomatous-tumor-well-differentiatedliposarcoma Slide 130: Di Muzio, B. and Gaillard et Al. Liposarcoma http://radiopaedia.org/articles/liposarcoma Slide 181: Roberts, C. Leiomyoma https://my.statdx.com/document/leiomyomasuperficial-and-deep/af4f8dc7-ea3b-44b6-a2f9-01cf915073c0?searchterm=leiomyoma Slide 183: Roberts, C. Fibrosarcoma, Soft Tissue https://my.statdx.com/document/fibrosarcoma-soft-tissue/d729ce6a-6cf8-4969-86ef- 346745391f5e?searchTerm=fibrosarcoma

Slide 188: Weerakkody et al. Intramuscular Myxoma http://radiopaedia.org/articles/intramuscular-myxoma Slide 190: Roberts, C. Myxofibrosarcoma https://my.statdx.com/document/myxofibrosarcoma/571b7935-5854-442a-933fbccd59a40b83?searchterm=myxofibrosarcoma Slide 194-196: Di Muzio, B. and Gaillard, F. et al. Synovial Sarcoma http://radiopaedia.org/articles/synovial-sarcoma

Chan WP. Magnetic resonance imaging of soft-tissue tumors of the extremities: A practical approach. World Journal of Radiology. 2013;5(12):455-459. doi:10.4329/wjr.v5.i12.455. Chen, K., Zhou, M., Yang, H., Qian, Z., Wang, G., Wu, G.... Sun, Z. (2013). Pre-operative embolization facilitating a posterior approach for the surgical resection of giant sacral neurogenic tumors. Oncology Letters, 6, 251-255. Chhabra and Soldatos. Soft-Tissue Lesions: When Can We Exclude Sarcoma? American Journal of Roentgenology. 2012;199: 1345-1357. 10.2214/AJR.12.8719 Wu JS, Hochman MG. Soft-tissue tumors and tumorlike lesions: a systematic imaging approach. Radiology 2009; 253:297 316 Wan, J., Magarelli, N., Peh, W. et al. Giant Cell Tumor of the Tendon Sheath Radiol med (2010) 115: 141. doi:10.1007/s11547-010-0515-2 Roberts, C. Glomus Tumor https://app.statdx.com/document/glomus-tumor/82f6482a- 26a9-43eb-8d97-98fdcc9330cd Roberts, C. Neurofibroma https://app.statdx.com/document/neurofibroma/4e6e518c-3828-429a-8552-7a56e41700d2 Roberts, C. Giant Cell Tumor of the Tendon Sheath https://my.statdx.com/document/giant-cell-tumor-tendon-sheath/55c34321-d2b1-4da7-b5cc-5a2eba5908ab Roberts, C, Lipoma https://my.statdx.com/document/lipoma-soft-tissue/24a2442ef539-483e-af31-33db5c3f8a66 Roberts, C. Lipomatosis https://my.statdx.com/document/lipomatosis/a7ef3528-5c36-4595-a693-68966edac95c Roberts C. Lipomatosis of a nerve https://my.statdx.com/document/lipomatosisnerve/d217207e-8933-4997-b884-b759d6caf025

Roberts, C. Leiomyoma https://my.statdx.com/document/leiomyoma-superficial-anddeep/af4f8dc7-ea3b-44b6-a2f9-01cf915073c0?searchterm=leiomyoma Roberts, C. Fibrosarcoma, Soft Tissue https://my.statdx.com/document/fibrosarcomasoft-tissue/d729ce6a-6cf8-4969-86ef-346745391f5e?searchterm=fibrosarcoma Roberts, C. Myxofibrosarcoma https://my.statdx.com/document/myxofibrosarcoma/571b7935-5854-442a-933fbccd59a40b83?searchterm=myxofibrosarcoma Walker, C. Elastofibroma https://app.statdx.com/document/elastofibroma/7b872a86-912f-455c-99c5-5be315bd63a2?searchterm=elastofibroma Di Muzio, B. and Gaillard, F. et al. Synovial Sarcoma http://radiopaedia.org/articles/synovial-sarcoma Banaster, M. Myositis Ossificans https://my.statdx.com/document/myositis-ossificansheterotopic-os-/d041548b-0dc9-4042-b056-3ebea0c7c3d1