Pathology: NTRK-rearranged spindle cell neoplasm

NTRK-rearranged spindle cell neoplasm

• Lobulated; spindle-stellate-epithelioid with fascicular-patternless arrangement

• Pale amphophilic cytoplasm

• Ovoid-round nuclei with mild pleomorphism and occasional multinucleation; occasional mitotic activity

• Variable myxoid-collagenous stroma; prominent ramifying capillary vasculature

• IHC: CD34, S100

• RNA-seq: LMNA::NTRK1 gene fusion

• PMID: 32050835

NTRK-rearranged spindle cell neoplasm

• Spindle cells with herringbone-storiform pattern

• Eosinophilic cytoplasm with long tapering processes

• Ovoid and elongated nuclei with mild atypia; mitotic activity

• Scant myxoid-collagenous stroma and a prominent ectatic thin-walled vasculature

• IHC: CD34, S100

• RNA-seq: TPM3::NTRK1 gene fusion

NTRK-rearranged spindle cell neoplasm

• Lobulated; spindle-epithelioid cells with vague fascicular pattern

• Abundant eosinophilic cytoplasm with indistinct cell borders

• Ovoid and elongated nuclei with a tapering end, prominent small nucleoli, marked pleomorphism and frequent multinucleation; mitotic activity

• Fibromyxoid stroma with occasional bundles of collagen and a mildinfiltrate of lymphocytes and eosinophils

• IHC: panTRK (negative)

• RNA-seq: HDGFRP3-NTRK3 gene fusion*

* To date unreported in the literature

NTRK-rearranged spindle cell neoplasm

• Infiltrative; spindle-stellate cells with fascicular-storiform pattern

• Pale amphophilic cytoplasm

• Ovoid-round nuclei with minimal pleomorphism; inconspicuous mitotic activity

• Myxoid-collagenous stroma; prominent capillary-like vasculature

• RNA-seq: LMNA::NTRK1 gene fusion