Common Diagnostic Challenges in the Histopathologic Diagnosis of Neuroendocrine Lung Tumors: A Case Report

Bronchopulmonary neuroendocrine tumors are an uncommon group of neoplasms, accounting for about 20% of all lung carcinomas, arising from stem cells of the bronchial epithelium known as Kulchitsky cells. In the past, these tumors were grouped among benign or less aggressive malignant pulmonary tumors. Currently, according to the 2004 World Health Organization categorization, these tumors are separated into 4 subtypes characterized by increasing biologic aggressiveness: low-grade (typical carcinoid; TC), intermediate-grade (atypical carcinoid; AC) and high-grade (large-cell neuroendocrine carcinoma, LCNEC, and small-cell lung carcinoma, SCLC). They differ by morphologic, immunohistochemical and structural features. At histopathologic analysis, these tumors share progressive increase in a number of mitotic figures per 10 high-power fields and in the extent of necrosis, with TC having the lowest values and SCLC having the highest. TCs and ACs make up approximately 1-2% of all primary lung tumors. Differentiating ACs from TCs or LCNEC and SCLC is clinically important because the treatment modalities and prognoses for these types of tumors are different. We report a case of misdiagnosis of bronchopulmonary neuroendocrine tumor in a young woman which has heavily influenced her clinical history.