Histologic changes: Further characteristics typical of small cell carcinomas are shown below.

Rosettes: This carcinoid tumor shows several rosettes--cells oriented around a tiny lumen (arrows). At least one other rosette is also present. These structures are very characteristic of neuroendocrine differentiation and may be found in all types of neuroendocrine tumors. While mucin may be demonstrated in the lumen, cytoplasmic mucin is absent. These structures are not evidence of differentiation to adenocarcinoma.

Trabecular growth pattern: Another characteristic pattern is the formation of narrow columns of cells separated by thin-walled vessels as shown here in this small cell carcinoma. This pattern, too, may be seen in any type of neuroendocrine tumor.

Clinical summary Cytology

Table of Contents