Carcinoid : Papillary Pattern
Carcinoids show a variety of growth patterns commonly seen in neuroendocrine tumors, including nesting, trabecular (most common), rosettes, papillary (shown here), pseudoglandular, follicular, and solid patterns. Peripheral tumors frequently show spindle cell pattern. Multiple patterns are usually seen in an individual case. The background stroma is highly vascular but may show hyalinization, calcification, mucin, amyloid, bone or cartilage formation.