Elsevier Pathology

Anatomic Pathology: Immunopathology

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1224) The metastatic adenocarcinoma of the adrenal gland shows strong nuclear staining for anti-PAX-8 suggestive of endometrial rather than pulmonary origin, which was confirmed by absence of an activating EGFR mutation previously detected in the pulmonary adenocarcinoma of the same patient. Which additional marker would BEST aid differentiating between pulmonary and endometrial adenocarcinoma?

• Napsin A is a pepsinlike protease present in type II alveolocytes and an additional marker for pulmonary adenocarcinoma, because thyroid transcription factor 1 (TTF-1) can be positive in many nonpulmonary carcinomas. The combination of TTF-1 and Napsin A shows maximum sensitivity and specificity with respect to identifying pulmonary adenocarcinomas by immunohistochemistry.

• Carcinoembryonic antigen (CEA) is positive in pulmonary adenocarcinomas and endometrial carcinomas with mucinous metaplasia and thus is not an optimal marker.

• Cytokeratins 5/6 mark squamous elements, which can occur in both forms of adenocarcinomas.

• The glycoprotein MUC5A though primarily present in the normal pulmonary and gastric mucosa is detected immunohistochemically in 22% of endometrial and 14% of pulmonary adenocarcinomas, respectively.

Ye J, Findeis-Hosey J, Yang Q, et al: Combination of Napsin A and TTF-1 immunohistochemistry helps in differentiating primary lung adenocarcinoma from metastatic carcinoma in the lung. Appl Immunohistochem Mol Morphol 2011;19:313-317.

Ye J, Hameed O, Findeis-Hosey J, et al: Diagnostic utility of PAX8, TTF-1 and Napsin A for discriminating metastatic carcinoma from primary adenocarcinoma of the lung. Biotech Histochem 2012;87:30-34.

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