Pathology: nodular fasciitis

Nodular fasciitis

  • Circumscribed; spindle cells with fascicular-storiform pattern

  • Pale amphophilic cytoplasm

  • Ovoid nuclei with minimal atypia and small nucleoli; occasional mitotic activity

  • Myxoid stroma with broad bands of collagen; mild chronic inflammation; extravasion of erythrocytes

  • IHC: smooth muscle actin

  • RNA-seq: MYH9::USP6 gene fusion

Nodular fasciitis

  • Circumscribed; spindle cells with fascicular-storiform pattern

  • Pale amphophilic cytoplasm

  • Ovoid nuclei with minimal atypia and small nucleoli; occasional mitotic activity

  • Myxoid stroma with broad bands of collagen; mild chronic inflammation; extravasion of erythrocytes

  • IHC: smooth muscle actin

  • RNA-seq: COL1A2::USP6 gene fusion

Nodular fasciitis

  • Lobulated; spindle cells with storiform pattern

  • Pale amphophilic cytoplasm

  • Ovoid nuclei with minimal atypia and small nucleoli; occasional mitotic activity

  • Mild chronic inflammation; focal myxoid degeneration

  • RNA-seq: MYH9::USP6 gene fusion

Nodular fasciitis

  • Circumscribed; spindle cells with vague fascicular-storiform pattern

  • Pale amphophilic cytoplasm

  • Ovoid elongated nuclei with minimal atypia and small nucleoli; occasional mitotic activity

  • Broad bands of collagen with focal myxoid degeneration; mild chronic inflammation

  • RNA-seq: MYH9::USP6 gene fusion

Nodular fasciitis

  • Circumscribed; spindle cells with fascicular-storiform pattern

  • Pale amphophilic cytoplasm

  • Ovoid elongated nuclei with minimal atypia and small nucleoli; occasional mitotic activity

  • Broad bands of collagen with focal myxoid degeneration; mild chronic inflammation

  • RNA-seq: MYH9::USP6 gene fusion

Nodular fasciitis

  • Spindle cells with storiform pattern

  • Pale amphophilic cytoplasm

  • Ovoid nuclei with minimal atypia and small nucleoli; occasional mitotic activity

  • Mild chronic inflammation; focal myxoid degeneration; focal extravasation of erythrocytes

  • RNA-seq: MYADM::USP6* gene fusion

* To date "MYADM-" is unreported in this context