[When salvage surgery for apparent "recurrence" of small-cell lung cancer leads to prolonged survival while correcting the initial diagnosis].

[INTRODUCTION] The distinction between small cell lung carcinoma (SCLC) and carcinoid tumors may be challenging in small biopsy specimens, particularly when cellular artefacts (crush artifact…) are present. Nevertheless, an accurate diagnosis of these two neuroendocrine neoplasms - whose prognoses are radically different - is crucial to ensure appropriate therapeutic management.

[CASE REPORT] We report the case of a 40-year-old female patient referred for salvage surgery for recurrent small cell lung carcinoma (SCLC). Confirmed histologically, the recurrence had been treated 44 months earlier with concurrent chemoradiotherapy and prophylactic cranial irradiation. For this apparent 'relapse', left pneumonectomy with extended radical lymphadenectomy including dissection around the recurrent laryngeal nerve was performed, achieving R0 resection. Final histopathological analysis revealed an atypical carcinoid tumor with lymph node involvement in stations 10 and 4L. Review of the initial pathology slides - on which the Ki-67 proliferation index had not been determined - revealed that the same tumor had been present from the outset. Ten and a half years after this procedure, the patient remains alive, with a bone recurrence diagnosed one year ago.

[CONCLUSION] Salvage surgery can correct an initial misdiagnosis and ultimately provide the patient with the appropriate treatment. Any clinico-radiological and pathological discordance should prompt either a repeat biopsy or an external expert review. Systematic use of the Ki-67 proliferation index for all diagnoses of pulmonary neuroendocrine tumours, particularly in small biopsy specimens, may help to avoid such diagnostic pitfalls.