Figure 1

Morphology of lung adenocarcinomas harboring ALK rearrangements. (a) Solid pattern with signet ring cells in a primary lung adenocarcinoma. Inset shows cells with intracytoplasmic mucin and peripherally displaced nuclei (hematoxylin and eosin; enlarged in inset). (b) Solid pattern with hepatoid tumor cells in a primary lung adenocarcinoma. Inset shows cells with abundant eosinophilic cytoplasm, round nuclei, and prominent nucleoli (hematoxylin and eosin; enlarged in inset). (c) Micropapillary and (d) papillary patterns in a primary lung adenocarcinoma (hematoxylin and eosin). (e) Papillary pattern with hepatoid tumor cells and focal signet ring cells (arrows) in a primary lung adenocarcinoma. Abundant extracellular mucin is present in this case (hematoxylin and eosin). (f) Solid pattern with signet ring cells in metastatic lung adenocarcinoma in a mediastinal lymph node, sampled by fine needle aspiration biopsy (hematoxylin and eosin).