Paragastric paraganglioma: a case report with unusual alveolar pattern and myxoid component.

Paragangliomas are neural crest-derived neuroendocrine tumors. Nearly 5 to 10% occur in extraadrenal sites, from the upper cervical region to the pelvis, related to the autonomic nervous system. Very few cases of gastric or paragastric paragangliomas have been reported. We report a paraganglioma attached to the stomach of an 85-year-old man. The tumor was 15 cm in diameter and was surgically resected via a subtotal gastrectomy. Fine-needle aspiration smears showed round epithelioid cells forming acini and spindle cells attached to capillaries. Occasional cells showed excentric nuclei and pale vesicular cytoplasm. Microscopically, the tumor was characterized by an alveolar and solid pattern of growth with some unusual features, such as myxoid stroma and pseudoalveoli that contained myxoid material. Spindle cells stained with vimentin and S-100 protein, whereas epithelioid cells showed diffuse cytoplasmic staining with chromogranin A. Electron microscopy of the tumor tissue revealed the presence of neurosecretory granules. To the best of our knowledge, this pattern of growth has yet to be described in the literature and may result in a misdiagnosis if sufficient immunohistochemical markers are not employed. We briefly discuss the cytomorphological features and differential diagnosis of this tumor, which was discovered in a rare location.