A typical carcinoid of the lung - a case report with pathological correlation and propagation of the cancer stem cell line BKZ1 with synaptophysin expression.

Rationale: Neuroendocrine tumors (NETs) of the lung account for 5% of all cases of lung cancer, which itself is the leading cause of cancer-related death worldwide. In accordance to its rarity, only few cell lines of NETs exist, which even often lack key characteristics of the primary tumor, making it difficult to study underlying molecular mechanisms.

Patient Concerns: The patient reported in this case is a 71-year old woman, which never smoked but suffered under dry cough.

Diagnoses: Chest CT-scan showed a paracardiac nodule of the lingula with 2 × 1.8 cm in diameter.

Interventions: The detected paracardiac nodule of the lingula was anatomically resected using video assisted thoracic surgery.

Outcomes: Histopathological diagnostic of the removed tissue identified the tumor as a well-differentiated typical carcinoid (TC), which represents one of the four subgroups of pulmonary NETs. Next to the successful treatment of the patient, we were able to propagate cancer stem cells (CSCs) out of the resected tumor tissue. To the best of our knowledge, we firstly isolated CSCs of a typical carcinoid, which were positive for the prominent CSC markers CD44, CD133 and nestin, confirming their stem cell properties. Additionally, CSCs, further referred as BKZ1, expressed the neuroendocrine marker synaptophysin, verifying their neuroendocrine origin. However, nuclear synaptophysin protein was also present in other stem cell populations, suggesting a role as general stem cell marker.

Lesson: In line with the importance of CSCs in cancer treatment and the lack of CSC-models for neuroendocrine neoplasms, the here described BKZ1 cancer stem cell line of a typical carcinoid represents a promising new model to study pulmonary carcinoids and particular NETs.