Combined small cell lung carcinoma and giant cell carcinoma: a case report

BACKGROUND Combined small cell lung carcinoma (SCLC) is defined as SCLC combined with elements of non-small cell lung carcinoma (NSCLC), accounting for approximately 30% of cases of SCLC. However, combined SCLC and giant cell carcinoma (GC) is very rare. CASE PRESENTATION A 50-year-old woman with a 45 pack-year smoking history was referred to our hospital for further investigation of an abnormal left hilar shadow. Chest computed tomography (CT) revealed a 28-mm solid pulmonary nodule in the left lower lobe and an enlarged left hilar lymph node adjacent to the left main pulmonary artery. CT-guided biopsy of the pulmonary nodule led to the diagnosis of high-grade neuroendocrine carcinoma. The preoperative clinical stage was defined as cT1bN1M0. Thus, the patient underwent left lower lobectomy with ND2a-2 lymph node dissection via thoracotomy. Pathological investigation revealed a 22-mm tumor and dense sheet-like growth of small tumor cells with scant cytoplasm and finely granular nuclear chromatin. Moreover, there was a sheet-like growth of bizarre, highly pleomorphic mono- or occasionally multinucleated giant cells, accounting for approximately 40% of the tumor. Both the small and giant cell components were thyroid transcription factor-1-positive and p40-negative and exhibited neuroendocrine differentiation, as indicated by positivity for synaptophysin and CD56 and negativity for chromogranin A. While the small cell component was E-cadherin-positive and vimentin-negative, the giant cell component was E-cadherin-negative and vimentin-positive, indicating an epithelial-to-mesenchymal transition. Only the small cell component was found within the mediastinal and hilar lymph nodes. The final pathological diagnosis was combined SCLC and GC, pT1bN2M0, and pStage IIIA. The patient received adjuvant chemotherapy with 4 cycles of cisplatin and irinotecan. No sign of recurrence has been noted for 1 year after the surgery. CONCLUSIONS This is the first detailed report of a unique case with combined SCLC and GC. The coexistence of SCLC and GC in the presented case might indicate several possibilities: (1) GC may arise from SCLC via epithelial-to-mesenchymal transition, (2) SCLC may arise from GC through phenotypic conversion, and (3) SCLC and GC may have derived from a common neuroendocrine origin. Further investigation is necessary to reveal the underlying pathological process.