Pathology: inflammatory myofibroblastic tumour

Circumscribed; cellular; fascicles of spindle-epithelioid cells

Pale amphophilic cytoplasm

Monomorphic ovoid nuclei with prominent nucleoli; occasional mitotic activity

Mild chronic inflammatory infiltrate

IHC: ALK1

RNA-seq: EML4::ALK gene fusion

Circumscribed; cellular; fascicles of spindle-epithelioid cells

Pale amphophilic cytoplasm

Monomorphic ovoid nuclei with prominent nucleoli; occasional mitotic activity

Mild chronic inflammatory infiltrate

IHC: ALK1

RNA-seq: IGFBP5::ALK gene fusion

Circumscribed; cellular; spindle cell fascicles

Eosinophilic cytoplasm

Monomorphic ovoid nuclei with prominent nucleoli; occasional mitotic activity

Mild chronic inflammatory infiltrate

RNA-seq: TNS1::ALK gene fusion

Cellular; spindle cell fascicles

Abundant pale amphophilic cytoplasm

Round-ovoid nuclei with prominent nucleoli and mild pleomorphism; occasional mitotic activity

Chronic inflammatory infiltrate

IHC: ALK1

RNA-seq: FN1::ALK gene fusion

Spindle-stellate-epithelioid cells in vague fascicules and clusters

Pale amphophilic cytoplasm

Ovoid-round nuclei with prominent nucleoli and mild pleomorphism; mitotic activity

Collagenous-myxoid stroma

Mixed inflammatory infiltrate, including lymphocytes, plasma cells, eosinophils and histiocytes

IHC: ALK1

RNA-seq: EML4::ALK gene fusion

Variable cellularity; spindle-stellate-epithelioid cells in vague fascicules and clusters

Pale amphophilic cytoplasm

Ovoid-round nuclei with prominent nucleoli and mild pleomorphism; conspicuous mitotic activity

Collagenous-myxoid stroma

Mixed inflammatory infiltrate, including lymphocytes, plasma cells, neutrophils, eosinophils and histiocytes

IHC: ALK1

RNA-seq: RRBP1::ALK gene fusion

PMID: 21164297