ALK rearrangement: a high-frequency alteration in ovarian metastasis from lung adenocarcinoma

BACKGROUND: Ovarian metastatic tumors from lung adenocarcinoma are rare, and a serial study of these tumors is lacking to date. Additionally, a better understanding of the clinicopathological and molecular characteristics of metastatic tumors is needed. METHODS: Seven cases of ovarian metastasis from lung adenocarcinoma from 2013 to 2017 at our institute were investigated. The results were combined with those found in literature review. A total of 16 cases were analyzed in the present study. We examined clinicopathological and immunohistochemical characteristics, further detected ALK rearrangement by FISH (fluorescence in situ hybridization), and assessed EGFR and KRAS mutations using Sanger sequencing or the amplification refractory mutation system (ARMS). RESULTS: The mean age of the patients was 44.6 years (range, 33–56 years). Eleven of sixteen patients developed ovarian tumors within a mean time of 18.5 months (range, 5–48 months) from the initial diagnosis of lung adenocarcinoma; 5 patients had lung tumors and ovarian masses simultaneously. Five tumors (5/16, 31%) occurred in the bilateral ovaries, and the others were unilateral ovarian tumors (11/16, 69%). All seven cases from our institute were positive for TTF-1 and Napsin A but negative for PAX8. In four cases, ALK (D5F3) was diffusely and strongly expressed, with ALK rearrangements (4/7, 57%). Overall, ALK rearrangement was found by FISH or immunohistochemistry in 11/16 (69%) cases. In two cases, EGFR mutations in exons 19 and 21, respectively, were found. One patient did not detected EGFR or ALK mutation in the metastatic tumor, but the primary lung adenocarcinoma did harbor an EGFR mutation. Two cases had no alterations in three genes above. Although the mean survival time of the patients with ALK rearrangement was longer than those without (mean survival time 25 m vs. 20 m), no statistical significance of the difference was found. CONCLUSIONS: As the largest case series of ovarian metastasis from lung adenocarcinoma, our findings indicate that ALK rearrangement is the most common molecular alteration. Although patients with ALK rearrangement appear to have a better prognosis than do those without ALK rearrangement, more cases with longer follow-up and multivariant analysis are needed to clarify this point.