Soft Tissue, Nodular fasciitis [LMP18721]

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Diagnostic Modality: 
Whole Slide Image
Disease Category: 
Neoplasia
Diagnosis: 
Nodular fasciitis
Species: 
Human
Organ System: 
Bones, Joints, and Soft-Tissue Tumours
Gender: 
Female
Age: 
19 years
Diagnosis Code: 
ICD-10: M72.4
Slide Contributor Information
Gao, A., Kiehl, TR.

Keywords

pseudosarcomatous fasciitis

Clinical History

19-year-old woman with left lateral clavicular mass.

Clinical Discussion

Nodular fasciitis is a benign, self-limited (myo)fibroblastic neoplasm characterized in most cases by USP6-MYH9 fusion, t(17;22). It occurs most commonly in young adults; intravascular and cranial variants occur in younger patients. Fascial surfaces and subcutaneous tissue of the upper extremity, trunk, and head/neck are common sites of involvement. Microscopically, the lesion is well-circumscribed with plump, spindled (myo)fibroblasts in short fascicular and loose storiform patterns. The cellularity varies widely; stroma may be collagenous or myxoid. Extravasated red blood cells, stromal lymphocytes, osteoclast-like giant cells are also common features. Mitoses may be numerous. Immunohistochemistry is diffusely positive for SMA; CD68 highlights intratumoural macrophages; desmin may be focally positive. This case was positive for the UPS6-MYH9 fusion.