Successful type-oriented endoscopic resection for gastric carcinoid tumors: A case report

Table 1 Histological tumor grading proposed by Rindi et al[14]

Grade 1a	Tumors characterized by small and microlobular-trabecular aggregates formed by regularly distributed, often aligned cells with regular monomorphic nuclei, usually inapparent nucleoli, rather abundant fairly eosinophilic cytoplasm and almost absent mitoses.
Grade 1b	Tumors characterized by significant areas with solid structure, absence of cell alignment, round to spindle cell shape, irregular and moderately polymorphic nuclei of larger size, often with evident nucleoli and rather few, morphologically typical mitoses.
Grade 2	Tumors showed prevalence of solid cellular aggregates and large trabeculae, crowding and irregular distribution of round to spindle and polyhedric tumor cells, fairly large vesicular nuclei with prominent eosinophilic nucleoli or smaller, hyperchromatic nuclei with irregular chromatin clumps and small nucleoli, considerable mitotic activity, sometimes with atypical mitotic figures and scant necrosis.
Grade 3	Tumors showed severe histological atypia with solid to diffuse structure and frequent central necrosis. They were composed of tightly packed, small to mid-sized tumor cells showing large, irregular, polymorphic and hyperchromatic nuclei, scant cytoplasm and frequent, often atypical, mitosis.