Paraneoplastic syndrome as the presentation of limited stage small cell carcinoma

Background: Small cell lung carcinoma (SCLC) is one of the deadliest forms of lung cancer due to its poor prognosis upon diagnosis, rapid doubling time, and affinity for metastasis. As 60-70% of patients with SCLC have disseminated disease upon presentation, it is imperative to determine the extent of disease burden for treatment. As a neuroendocrine carcinoma, clinicians must pay close attention to abnormal findings in a smoker that could lead to earlier diagnosis and better prognostication.

Case presentation: A 64 year-old 20-pack year smoker presented to the emergency department with nausea and vomiting for 3 days. No inciting events were elicited. History and review of symptoms were negative including symptoms most-commonly associated with malignancy such as fevers and weight loss. He also denied any pulmonary symptoms. Physical examination was benign except for right lung end-expiratory wheezing. Our patient was clinically euvolemic. Initial blood laboratories showed a sodium 110, serum osmolarity 227, and urine osmolarity of 579. Fluid restriction led to normalization of his sodium and resolution of nausea & vomiting. Chest radiography was obtained to follow-up on the wheezing, which was read as no acute cardiopulmonary disease by radiology. Due to high suspicion of SIADH from malignancy, a CT of the chest was performed which showed a conglomerate of nodules and opacities in the right upper lobe. Biopsy revealed SCLC. At outpatient follow-up, patient had a PET-CT showing one active mediastinal lymph node as the only site of metastasis. He received three round of chemotherapy, chest and prophylactic cranial radiation, and deemed in remission by oncology.

Discussion and conclusions: Due to its affinity for metastases, 70% of patients with SCLC present with symptoms related to the spread of cancer to affected organ systems. Given the aggressive nature of this disease, screening measures have been implemented to help diagnose limited stage SCLC. Unfortunately, in our patient and many others, screening guidelines may fail to identify appropriate patients to scan. It is therefore imperative to use our clinical index of suspicion and identify any early presentations (including paraneoplastic syndromes) which may tip off the beginning stages of SCLC. This could improve survival rates by up to 45%.