Objective:

To describe variation in morphology, immunohistochemical findings, and clinical course in two patients with pulmonary NUT carcinoma.

Approach:

• Cases: The authors reviewed tumor morphology, squamous differentiation, immunostaining, treatment, disease progression, and survival in two patients.
• Diagnostic assessment: Testing included NUT, AE1/AE3, CAM5.2, p63, and p40 immunostaining, as well as Ki-67 labeling.

Key Findings:

• One tumor showed prominent squamous differentiation and AE1/AE3 and CAM5.2 positivity; the other had only small foci of squamous differentiation, limited AE1/AE3 staining, and negative CAM5.2 staining.
• Both tumors were positive for p63, p40, and NUT. Ki-67 labeling indices were approximately 30% and 50%.
• Both patients developed aggressive disease progression and died: one 5 months after admission and the other 1 year after surgery.
• The authors cited prior analyses reporting squamous differentiation in 33% of 124 NUT carcinoma cases and absent keratin expression in approximately 20%.

Interpretation:

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

Limitations:

• The report included only two patients and was descriptive, so it cannot establish how frequently these features occur.
• Differences in tissue sampling and retrospective confirmation of the first diagnosis complicated direct comparison.

Conclusion:

The authors reported no funding or conflicts of interest.

Sources:

• Case Reports in Pathology