MIMICS OF SOFT-TISSUE SARCOMA: PSEUDOTUMORS

INTRODUCTION

NODULAR FASCIITIS

• Benign proliferation of fibroblasts
• Most common lesion of fibrous tissue
• Generally presents as a rapidly growing solitary mass
• Most common in age group 20-35 years
• Males = Females
• Occurs in upper extremity (forearm), chest wall, back
• Head and neck site more common in children
• Generally < 3 cm in size, rarely larger size
• Occurs in subcutaneous, intramuscular, fascial locations
• Treated by local excision, spontaneous regression possible

Click on image(s) to view JPEG image(s).
	Patient 1 39-year-old male with surgically proven nodular fasciitis of right upper arm.
1.	T1W MR image reveals heterogenous intermediate signal intensity mass (arrow on JPEG image) in posterior right upper arm.
2.	T2W MR image reveals high signal intensity mass mimicking sarcoma. MRI findings in nodular faciitis are nonspecific and biopsy is necessary to establish diagnosis. Proliferative myositis or fasciitis may also present as masses.
3.	Contrast enhanced CT scan reveals mass with central low attenuation. Low attenuation on CT scan in nodular fasciitis has been attributed to myxomatous tissue component.
4.	Representative photomicrograph from cellular portion of tumor reveals haphazardly arranged proliferation of spindle shaped fibroblastic cells. (Original magnification, X160 H-E stain)
5.	Representative photomicrograph from central portion of tumor reveals loose connective tissue with a myxoid background. The histological characteristics grossly correspond to the signal intensity changes noted on the MR images. (Original magnification, X120 H-E stain).
6.	Photograph of histological cut section reveals cellular periphery and cystic central region (arrow on JPEG image).