Onkológia 2/2017

Importance of immunohistochemistry and application of TTF-1 and napsin A in differential diagnosis of primary pulmonary adenocarcinomas and pulmonary metastases of extrapulmonary origins

The differential diagnosis between primary and secondary pulmonary adencarcinomas is daily requisiton for pathologist. Lungs are the most common site of metastases from various primary and primary pulmonary adenocarcinomas are one of the most common worldwide malignancies. Immunohistochemistry is useful method to determine the origin of tumor in case when histomorphology alone is insufficient in poor differentatied carcinomas. Accordingly, presence of enteric, clear cell, spindle cell and signet-ring cell features complicates determinating of origin of adenocarinomas. The most common and long-used lung specific immunohistochemical marker is TTF-1, but specificity and sensitivity is not 100%. Use of TTF-1 has pitfalls that complicate its routine use. TTF-1 alone is insufficient marker for determinating of origin of adenocarcinoma in the lung. Newly used immunohistochemical marker is napsin A. According to many authors is sensitivity and specificity for napsin A higher than TTF-1. Use of TTF-1 and napsin A simmultaneously increases sensitivity up to 85% for primary lung adenocarcinomas. Both immunohistochemica lmarkers can be expressed in various tumours of extrapulmonary origin that can metastasize to lung, thus specificity is not 100%. In cases of surgical resection of tumor wider panels of immunohistochemical antibodies are used. Small biopsies and cythological material is quantitative restricted and sometimes qualitatively deficient. It is sometimes complicated and even impossible for pathologist to determine primary origin of tumor.

Keywords: differential diagnosis, immunohistochemistry, lung adenocarcinoma, metastasis, TTF-1, napsin A