Expression of developing neural transcription factors in diffuse idiopathic pulmonary neuroendocrine cell hyperplasia (DIPNECH).

DIPNECH is characterized by neuroendocrine cell hyperplasia, tumorlets, and eventually carcinoid tumors. Although it is regarded by some authors as a preneoplastic condition, this issue is controversial. New pathologic criteria have recently been proposed for the diagnosis of DIPNECH, and a subgroup of carcinoid tumors expressing developing neural transcription factors (DNTFs), with clinicopathologic features similar to those of DIPNECH, has been recognized. This paper reports on the clinical and pathological findings in three cases of DIPNECH and investigates the expression of three DNTFs (TTF1, ASCL1, and POU3F2). All patients were female, with a mean age of 63 years, and all lesions were located in the periphery of the lung. In two cases, typical carcinoids were associated with a spindle-cell component. All neuroendocrine proliferations were DNTF positive. The morphologic (spindle-cell component), phenotypic (DNTF expression), and clinicopathologic (peripheral tumors, female predominance) similarities suggest that DIPNECH may be a preneoplastic lesion for peripheral carcinoids.