Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH).

Diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH) is a pre-invasive generalized proliferation of pulmonary neuroendocrine (PNE) cells, which has been described in combination with carcinoid tumorlets, obliterative bronchiolitis, and other fibrotic lung changes. Since its first recognition as a distinct syndrome in 1992, variable clinico-pathologic features have been used to diagnose DIPNECH in small case series and case reports. We recently proposed the use of the following criteria for the pathologic diagnosis of the syndrome on lung resection specimens: the presence of multifocal neuroendocrine cell hyperplasia, as defined by the presence of 5 or more PNE cells in at least 3 separate small airways combined with 3 or more carcinoid tumorlets. At diagnosis, 53% of DIPNECH patients present with a synchronous carcinoid tumor and 24% have obliterative bronchiolitis. To our knowledge, only 1 patient has been diagnosed with a carcinoid tumor subsequent to a DIPNECH diagnosis and the syndrome is not associated with an increased incidence of high-grade neuroendocrine neoplasms. Patients have usually a stable disease and only 26% experience clinical and/or radiographic deterioration. There is no evidence that treatment with octreotide or other medications improves the prognosis of DIPNECH patients.