Coexistence of DIPNECH with pulmonary adenocarcinoma: Coincidence or by design?

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) coexisting with pulmonary adenocarcinoma (ADC) is rare. Herein, we report a new case and review the cases published previously in the English literature. The clinicopathological features of similar cases reported in the English literature were summarized, and a putative association between DIPNECH and pulmonary ADC was suggested. Among the 22 cases studied, the majority of patients were female and older adults. DIPNECH lesions were usually recognized beyond the lobe or segment in which the ADC was located. Most ADCs were of a low- or intermediate-grade. DIPNECH and pulmonary ADC were interspersed in six patients. In particular, two cases of ADC showed neuroendocrine differentiation. We consider that DIPNECH accompanied by ADC is not coincidental, and that the two lesions may have a causal relationship. Analogous to the tumor histogenesis association of large cell neuroendocrine carcinoma/small cell carcinoma with ADC, we hypothesized that DIPNECH may also arise from a multipotent precursor cell and associate with a subgroup of ADC. However, further studies are required to explore this possibility.