Anaplastic Lymphoma Kinase (ALK) Rearrangement-positive Lung Cancer with Transformation to Pleomorphic Carcinoma

Overexpression of CD 133 and BCL-2 in non-small cell lung cancer with neuroendocrine differentiation after transformation in ALK rearrangement-positive adenocarcinoma

Transformation to small cell lung cancer is one phenomenon of acquired resistance to anaplastic lymphoma kinase (ALK) tyrosine kinase inhibitors in ALK rearrangement-positive non-small cell lung cancer (NSCLC). Few case reports have focused on other types of histological transformation. We report a case of transformation of ALK rearrangement-positive adenocarcinoma to NSCLC with neuroendocrine differentiation during alectinib therapy. A 36-year-old woman presented with a tumor in the left lower lobe and bone metastases. She was diagnosed with ALK rearrangement-positive adenocarcinoma by histopathology of the primary tumor. Alectinib had been effective for 8 months before new lesions appeared. Histopathological re-examination of a recurrent tumor revealed poorly differentiated carcinoma with insulinoma-associated protein 1 (INSM1) expression, which remained ALK-positive. Expression of CD133, BCL-2, and SOX2 was positive in comparison to the initial tumor. Expression of SOX2 became more strongly positive than it was before treatment. The immunohistochemical findings of these markers associated with cancer stem-like cells and/or neuroendocrine differentiation suggest that cancer stem cells play a role in the mechanisms of histological transformation and acquired resistance of ALK rearrangement-positive cancer. To our knowledge, this is the first report to suggest an association between cancer stem-like cells and histological transformation in ALK rearrangement-positive lung cancer.

Copy number gain in recurrent anaplastic lymphoma kinase (ALK) rearrangement-lung adenocarcinoma in the pleural effusion

Copy number gain (CNG), which includes both numerical and structural chromosomal abnormalities, has been investigated in many human cancers. We report a case of recurrence of anaplastic lymphoma kinase (ALK) rearrangement-positive lung adenocarcinoma with increased cellular pleomorphism and ALK copy number in pleural effusion cytology, and retrospectively compared the recurrent tumor with the primary tumor in terms of cytological features, immunohistochemistry (IHC) and fluorescence in situ hybridization (FISH). The patient was a woman in her 50s who was found to have a 20 × 20 mm sized mass in the lung by chest computed tomography (CT), and was diagnosed with ALK rearrangement-positive lung adenocarcinoma. The patient was administered ALK inhibitors, such as alectinib, however 4 years later dissemination to the pleural effusion was detected. The smear was of high cellularity, and a predominant population of large-sized pleomorphic adenocarcinoma cells with prominent nucleoli was observed. On FISH and IHC using cell block material, ALK rearrangement and ALK protein expression were identified again, along with recurrent ALK adenocarcinoma cells, which were observed to have an increased ALK copy number compared with the primary ALK adenocarcinoma cells. On the other hand, there was no discrepancy in the expression of various biomarkers between the primary and corresponding recurrent tumor. The present case showed a marked difference in cytological findings and CNG between the primary and recurrent tumor, indicating that DNA aneuploidy may be related to morphological change such as transformation to bizarre pleomorphic cells in patients receiving alectinib treatment.