Differential diagnosis of calcitonin-secreting neuroendocrine carcinoma ofthe foregut by pentagastrin stimulation

Background and aims: This study assessed the suitability of pentagastrin st imulation in hyper-calcitoninaemia for differential diagnosis of neuroendoc rine carcinoma of the foregut. Patients: A prospective institutional study (March 1997-September 1999) was conducted involving all patients admitted t o the pneumological and general surgical wards for small cell lung cancer ( SCLC) or primary medullary thyroid carcinoma (MTC). Basal and stimulated se rum calcitonin levels were measured using an improved immunoradiometrical a ssay for the monomeric form of calcitonin. Results: Increased basal calcito nin levels were noted in six non-MTC patients (one mediastinal and one lary ngeal neuroendocrine carcinoma, and four SCLCs). Because of chronic renal f ailure, one SCLC patient had to be excluded. The remaining five non-MTC pat ients with normal renal function were compared to eight primary MTC patient s. In terms of pentagastrin stimulation, an increase in serum calcitonin le vels of less than twofold the baseline significantly correlated with both n on-MTC (r=0.85; P=0.005) and SCLC (r=0.81; P=0.024). Immunostaining of tiss ue specimens for calcitonin was positive in the patients with mediastinal a nd laryngeal neuroendocrine carcinoma and in all eight patients with primar y MTC, but was negative in the two SCLC patients with adequate tissue sampl es. Conclusions: Irrespective of the pathophysiological background, pentaga strin stimulation affords a differential diagnosis in neuroendocrine carcin oma of the foregut when chronic renal failure is excluded.