Primary mixed adenocarcinoma and small cell carcinoma of the appendix: a clinicopathologic, immunohistochemical, and molecular study of a hitherto unreported tumor.
Appendiceal carcinoids range from well-differentiated endocrine tumor to well-differentiated endocrine carcinoma, while poorly differentiated (small cell) carcinoma has not been described in this site. We report herein a case of mixed intestinal-type adenocarcinoma associated with a small cell carcinoma arisen in a 35-year-old woman and clinically presenting as an appendiceal abscess. The resected tumor histologically appeared as a biphasic lesion composed of a nonmucinous adenocarcinoma closely juxtaposed with a poorly differentiated (small cell) endocrine carcinoma. The subsequent right hemicolectomy was unremarkable, but one pericolic lymph node showed a metastatic deposit consisting of the adenocarcinoma only. The patient thus underwent a chemotherapeutic protocol for colorectal cancer, and she is alive and well at the 65-month follow-up. Immunohistochemically, the adenocarcinoma strongly stained for cytokeratin 20 and carcinoembryonic antigen, while the endocrine component displayed a dot-like positivity for pan-cytokeratins and chromogranin. Of note, both components did not stain with CDX2 and p53. At genotypic analysis by microsatellite instability, both components shared many microsatellite alterations as well as a normal p53 gene setup, although small cell carcinoma harbored additional alterations. Clinical and molecular findings led us to consider this lesion as a clonal tumor in which the endocrine component seems to derive from a progressive differentiation of the adenocarcinoma following a glandular-to-endocrine sequence.
Department of Pathologic Anatomy and Legal Medicine, Section of Pathology, University of Modena and Reggio Emilia, Italy. giulio@unimo.it
Giulio
G
Rossi
Federica
F
Bertolini
Giuliana
G
Sartori
Nazzarena
N
Bigiani
Alberto
A
Cavazza
Moira
M
Foroni
Riccardo
R
Valli
Guido
G
Rindi
Carmela
C
De Gaetani
Gabriele
G
Luppi
D000230:Adenocarcinoma / Q000473:pathology*; D000328:Adult; D001063:Appendiceal Neoplasms / Q000235:genetics / Q000473:pathology*; D018288:Carcinoma, Small Cell / Q000235:genetics / Q000473:pathology*; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D009378:Neoplasms, Multiple Primary / Q000235:genetics / Q000473:pathology*