ALK-Rearranged renal neoplasms: update on an institutional cohort

Anaplastic lymphoma kinase-rearranged renal cell carcinoma (ALK-RCC) is a rare and recently recognized molecular subtype of RCC defined by ALK gene fusions. We describe five ALK-RCC and one likely ALK-rearranged epithelioid mesenchymal neoplasm from both pediatric and adult patients. Tumors exhibited diverse morphologic features, including papillary, mucinous, and cribriform patterns. ALK expression was confirmed in all cases by immunohistochemistry. Molecular profiling revealed several fusion partners including ARNT, EML4, NUMA1, TPM3, and VCL. A single patient with a VCL::ALK gene rearrangement had sickle cell trait. Novel gene rearrangements in RCC include NUMA1::ALK and ARNT::ALK. Metastatic disease was documented in three patients, and two died of disease. This series underscores the morphological heterogeneity of ALK-RCC (including frequent papillary and mucinous features), is informative of novel fusion partners such as NUMA1 and ARNT, further highlights the association of the VCL::ALK fusion with sickle cell trait, and is informative of the natural history of disease in a subset of patients.