A comparative study of generic stains for carcinoid secretory granules

Generic stains for secretory granules in carcinoid tumors often yield inconsistent and unpredictable results. Consequently, these techniques have been modified and new ones devised; however, very few studies comparing the efficacy of the various methods have been published. To determine which method would most consistently demonstrate carcinoid granules, we applied a battery of six stains to 73 tumors, all morphologically identified as carcinoids, from various sites (17 pulmonary, 13 small intestinal, 20 appendiceal, 18 rectal, five miscellaneous). Stains employed included four argyrophil (Sevier-Munger, Grimelius, Pascual, Churukian-Schenk), one argentaffin (Fontana-Masson), and one non-silver technique (lead hematoxylin). Of the 73 carcinoids, 97% stained positively with the Churukian-Schenk, 82% with the Pascual, 79% with the Grimelius, 74% with the Sevier-Munger, 67% with lead hematoxylin, and 51% with the Fontana-Masson technique. The two cases negative by the Churukian-Schenk technique were also negative with all other stains; thus, this technique most consistently demonstrated secretory granules in carcinoids, including all 18 rectal tumors. The Churukian-Schenk method achieves its superior results by reducing background staining and nonspecific precipitation to a level that permits sparse, small granules to be readily identified. In control sections of normal mucosa and in some tumors, this stain revealed more than one population of argyrophil cells as identified by the size, color, and staining intensity of the granules.