Carcinoid syndrome is an extremely rare paraneoplastic disorder associated with serotonin-secreting neuroendocrine tumors, which classically present with flushing, weight loss, hypertension, and gastrointestinal complaints. In fact, symptoms are often nonspecific, and the presentation could promote confusion with hematologic or inflammatory diseases. Early diagnosis is of great importance in allowing proper therapy to avoid delays.

A 45-year-old female was referred to the hematology clinic owing to high WBC count (21,000/µL), associated with fatigue, flushing, and unintentional weight loss of 10 kg over the past 3-4 months. Her history included hypothyroidism on thyroxin and asthma—both on symptomatic medications. Gastroenterology work-ups, including endoscopy, showed mild antral gastritis and a hiatal hernia but no evidence of malignancy.

Thus, the imaging studies demonstrated a low-density nodule measuring 1 cm in size on the right adrenal gland, hence the suspicion of a neuroendocrine tumor. Excess serotonin production was confirmed by demonstrating a 24-hour urinary 5-HIAA level of 18.7 mg/day, with a reference range being 2-9 mg/day, compatible with carcinoid syndrome. Confirmatory Ga-68 DOTA-TATE PET-CT revealed moderate increased somatostatin receptor expression in the adrenal lesion. No anemia or other hematologic disorders were observed, despite the initial suspicion of one.

This case highlights carcinoid syndrome as a potential cause of systemic symptoms such as flushing, weight loss, and leukocytosis, even in cases referred for suspected hematologic conditions. Confirmation was based on the elevated level of 5-HIAA and advanced imaging with Ga-68 DOTA-TATE PET-CT. This report emphasizes the need for interdisciplinary collaboration between hematology, endocrinology and oncology for managing complex systemic cases. Early diagnosis of carcinoid syndrome ensures appropriate care, prevents misdiagnosis, and improves outcomes.