Task: Instance Description Understanding (ontology: Sciences/Computer_Science)

Which of the following definitions best describes the instance 'pN0 (lung)'?

A. A pathologic lymph node stage for lung according to AJCC 7th edition indicating metastasis in ipsilateral mediastinal and/or subcarinal lymph node(s).
B. A pathologic lymph node stage for lung according to AJCC 7th edition indicating no regional lymph node metastasis.
C. A pathologic lymph node stage for lung according to AJCC 7th edition indicating metastasis in ipsilateral peribronchial and/or ipsilateral hilar lymph nodes and intrapulmonary nodes, including involvement by direct extension.
D. A pathologic lymph node stage for lung according to AJCC 7th edition indicating metastasis in contralateral mediastinal, contralateral hilar, ipsilateral or contralateral scalene, or supraclavicular lymph node(s).

Answer: A pathologic lymph node stage for lung according to AJCC 7th edition indicating no regional lymph node metastasis.