Neuroendocrine carcinoma of the paranasal sinus: a morphological and endocrinological study.

Four cases of small cell carcinoma of the paranasal sinuses were studied histologically, ultrastructurally, and endocrinologically. All tumors showed features of undifferentiated carcinoma with alveolar patterns but without acinar or squamous differentiation and contained cells possessing endocrine-type small secretory granules, which were indistinguishable from non-neoplastic neurosecretory granules. The three cases also possessed a small number of microtubules, and in one of these fine cytoplasmic filaments were observed. One case showed elevated plasma levels of cortisol and adrenocorticotropic hormone associated with adrenocortical hyperplasia and Crooke's changes of the pituitary gland. Another case showed hypercalcemia with bone metastasis, hypercalcitonemia with a high content of calcitonin in the tumor tissue, calcitonin-positive tumor cells, and C-cell hyperplasia of the thyroid. It was concluded that all four cases should be called neuroendocrine carcinoma, which might be related to neoplasms derived from amine precursor uptake and decarboxylation cell series rarely encountered in the paranasal sinuses.