NUT carcinoma may defy typical staining patterns

Two pulmonary cases highlight how limited squamous differentiation and variable keratin expression may complicate pathological diagnosis.

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Two pulmonary NUT carcinomas showed markedly different morphology and immunohistochemical profiles despite sharing the same diagnosis.
2

One tumor had prominent squamous differentiation and AE1/AE3 and CAM5.2 positivity, whereas the other had only small squamous foci, limited AE1/AE3 staining, and no CAM5.2 staining.
3

Both tumors expressed p63 and p40, and NUT immunostaining confirmed the diagnosis in each case.
4

Both patients developed aggressive metastatic disease and died within 5 months to 1 year despite treatment.
5

The authors stated that negative keratin staining or inconspicuous squamous differentiation does not exclude NUT carcinoma and that diagnosis relies on NUT immunohistochemistry or molecular testing.

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