Cytology meets next generation sequencing and liquid biopsy: A case of lung adenocarcinoma presenting as metastasis to the phalanx

Carcinomas do rarely metastasize to the finger. Non-small-cell lung cancer is most frequently involved. To date, only a few cases have been reported, on histology. Here we describe the cytological features of a metastatic lung adenocarcinoma case to the phalanx of the right forefinger as initial manifestation of the neoplastic disease in a 69-years-old woman. The cytological microscopic findings, complemented by a wide array of ancillary techniques, were confirmed by histology. Neoplastic cells were positive for cytokeratin 7 (CK7) and thyroid transcription factor 1 (TTF-1), harboring, in tissue and in bloodstream samples, an uncommon epidermal growth factor receptor (EGFR) exon 20 p.S768_D760DUP, detected by next generation sequencing (NGS) and liquid biopsy. Cytology corroborated by immunocytochemistry, NGS, and liquid biopsy is a modern approach to provide diagnostic and therapeutic information even in rare and challenging cases.