Pathology: desmoid fibromatosis

Desmoid fibromatosis

• Fascicles of spindle-stellate cells

• Eosinophilic cytoplasm 

• Ovoid nuclei with pinpoint nucleoli; inconspicuous mitotic activity

• Keloid-like collagenous matrix with prominent small vessels 

• IHC: beta-catenin 

• DNA-seq:  CTNNB1 mutation (c.121A>G; p.T41A)

Desmoid fibromatosis

Familial adenomatous polyposis 

• Spindle-stellate cells with storiform pattern

• Eosinophilic cytoplasm 

• Ovoid nuclei with pinpoint nucleoli; inconspicuous mitotic activity

• Collagenous matrix with prominent small vessels

• IHC: smooth muscle actin, beta-catenin 

Desmoid fibromatosis

• Spindle-stellate cells with storiform pattern

• Eosinophilic cytoplasm 

• Ovoid nuclei with pinpoint nucleoli; inconspicuous mitotic activity

• Collagenous matrix with prominent small vessels 

• DNA-seq:  CTNNB1 mutation (c.121A>G; p.T41A)

Desmoid fibromatosis

• Fascicles of spindle-stellate cells

• Eosinophilic cytoplasm 

• Ovoid nuclei with pinpoint nucleoli; inconspicuous mitotic activity

• Collagenous matrix with prominent small vessels 

• DNA-seq:  CTNNB1 mutation (c.121A>G; p.T41A)

Desmoid fibromatosis

• Infiltrative; long sweeping fascicles of spindle-stellate cells

• Eosinophilic cytoplasm with long tapering processes

• Ovoid nuclei with pinpoint nucleoli; occasional mitotic activity

• Abundant collagenous matrix with prominent small vessels with perivascular oedema 

• DNA-seq:  CTNNB1 mutation (c.121A>G; p.T41A)

Desmoid fibromatosis

• Lobulated; spindle-stellate cells with vague fascicular pattern

• Eosinophilic cytoplasm with long bipolar processes

• Ovoid and elongated wavy nuclei with pinpoint nucleoli; occasional mitotic activity

• Abundant collagenous matrix, including "keloid-like" collagen

• Delicate thin-walled vasculature

Desmoid fibromatosis

• Infiltrative; spindle-stellate cells with vague fascicular pattern

• Eosinophilic cytoplasm with long tapering processes

• Ovoid and wavy nuclei with pinpoint nucleoli; occasional mitotic activity

• Abundant collagenous matrix with prominent small vessels

Desmoid fibromatosis

• Spindle-stellate cells with vague fascicular pattern

• Eosinophilic cytoplasm with long tapering processes

• Ovoid and buckled nuclei with pinpoint nucleoli; inconspicuous mitotic activity

• Abundant collagenous matrix with prominent small vessels

• IHC: beta-catenin

Desmoid fibromatosis

• Spindle-stellate cells with vague fascicular pattern

• Eosinophilic cytoplasm with long tapering processes

• Ovoid nuclei with pinpoint nucleoli; inconspicuous mitotic activity

• Abundant "keloid-like' collagenous matrix with prominent small vessels

• IHC: beta-catenin

• DNA-seq:  CTNNB1 exon 3 mutation; c.121A>G (p.T41A)

Desmoid fibromatosis

• Spindle-stellate cells with vague fascicular pattern

• Eosinophilic cytoplasm with long tapering processes

• Ovoid and wavy nuclei with pinpoint nucleoli; inconspicuous mitotic activity

• Abundant collagenous matrix with prominent small vessels

• IHC: beta-catenin

Desmoid fibromatosis

• Infiltrative; spindle-stellate cells with vague fascicular pattern

• Eosinophilic cytoplasm with long tapering processes

• Ovoid and wavy nuclei with pinpoint nucleoli; occasional mitotic activity

• Abundant collagenous matrix with prominent small vessels; entrapment of glandular epithelium