Cytomorphological features of ALK-positive lung adenocarcinomas: psammoma bodies and signet ring cells.

Abstract

Correlation between histology and genotype has been described in lung adenocarcinomas. For example, studies have demonstrated that adenocarcinomas with an anaplastic lymphoma kinase (ALK) gene rearrangement may have mucinous features. The objective of the current study was to determine whether a similar association can be identified in cytological specimens. A retrospective search for ALK-rearranged cytopathology (CP) and surgical pathology (SP) lung carcinomas was conducted. Additional ALK-negative (-) lung adenocarcinomas served as controls. For CP and SP cases, the clinical data (i.e., age, sex, and smoking history), architecture, nuclear features, presence of mucin-containing cells (including signet ring cells), and any additional salient characteristics were evaluated. The search yielded 20 ALK-positive (+) adenocarcinomas. Compared with patients with ALK(-) lung adenocarcinomas (33 patients; 12 with epidermal growth factor receptor [EGFR]-mutation, 11 with Kristen rat sarcoma [KRAS]-mutation, and 10 wild-type adenocarcinomas), patients with ALK(+) adenocarcinoma presented at a younger age; and there was no correlation noted with sex or smoking status. The most common histological pattern in SP was papillary/micropapillary. Mucinous features were associated with ALK rearrangement in SP specimens. Signet ring cells and psammoma bodies were evident in and significantly associated with ALK(+) SP and CP specimens. However, psammoma bodies were observed in rare adenocarcinomas with an EGFR mutation. Both the ALK(+) and ALK(-) groups had mostly high nuclear grade. Salient features, including signet ring cells and psammoma bodies, were found to be significantly associated with ALK(+) lung adenocarcinomas and are identifiable on CP specimens. Recognizing these may be especially helpful in the molecular triage of scant CP samples.