Carcinoid : Nesting Pattern
Carcinoids show a variety of growth patterns commonly seen in neuroendocrine tumors, including nesting (shown here), trabecular (most common), rosettes, papillary, 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. The nesting pattern seen here resembles paraganglioma. The presence of S-100 positive cells may further add to confusion in such cases.