title: Composite intestinal adenoma-microcarcinoid clues to diagnosing an under-recognised mimic of invasive adenocarcinoma.
abstract: OBJECTIVE
  Microcarcinoids refer to microscopic nests of monotonous cells with endocrine and squamoid features. Their peculiar morphology can appear infiltrative with a desmoplastic-like background, raising concerns for an infiltrating adenocarcinoma. To further characterise microcarcinoids, we undertook a prospective clinicopathological study.
  
  
  METHODS
  11 specimens originating from five men and six women (average age=58.9 years) were prospectively collected from December 2004 to December 2011.
  
  
  RESULTS
  Microcarcinoids were most commonly identified in high-risk adenomas (size ≥10 mm (n=10), villous components (n=8) and/or high-grade dysplasia (n=4)). All polyps had mucosal prolapse and four displayed background fibrosis reminiscent of desmoplasia. The microcarcinoid component was most often multifocal (n=7) within the individual polyp and extended over an average length of 3.9 mm. The individual microcarcinoid cells were cuboidal with abundant eosinophilic cytoplasm. All cases had monotonous nuclei which lacked pleomorphism, hyperchromasia and mitotic activity. All available microcarcinoids were β-catenin and synaptophysin reactive and non-reactive for chromogranin and p53 with a negligible Ki-67 proliferation index (<2%). In addition, the microcarcinoids were variably reactive for p63 and/or CK 5/6, thereby demonstrating focal squamoid features. Two of the study cases were submitted with a concern for invasive carcinoma. Clinical information was available in 10 patients with up to 24 months of follow-up: all patients are alive and well and no subsequent malignancy has been reported.
  
  
  CONCLUSIONS
  Awareness of this unique morphology is important to avoid overdiagnosing microcarcinoids as invasive adenocarcinoma. Moreover, this immunohistochemical panel can be helpful in discriminating microcarcinoids from its malignant mimic in challenging cases.
authors: Department of Pathology, Johns Hopkins School of Medicine, Baltimore, Maryland, USA.
authors: Safia N
authors: SN
authors: Salaria
authors: Amer K
authors: AK
authors: Abu Alfa
authors: Nada Y
authors: NY
authors: Alsaigh
authors: Elizabeth
authors: E
authors: Montgomery
authors: Christina A
authors: CA
authors: Arnold
mesh_terms: D000230:Adenocarcinoma / Q000737:chemistry / Q000145:classification / Q000473:pathology*; D000236:Adenoma / Q000737:chemistry / Q000145:classification / Q000473:pathology*; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D014408:Biomarkers, Tumor / Q000032:analysis; D002276:Carcinoid Tumor / Q000737:chemistry / Q000145:classification / Q000473:pathology*; D049109:Cell Proliferation; D003937:Diagnosis, Differential; D005260:Female; D005355:Fibrosis; D006801:Humans; D007150:Immunohistochemistry; D007414:Intestinal Neoplasms / Q000737:chemistry / Q000145:classification / Q000473:pathology*; D007417:Intestinal Polyps / Q000737:chemistry / Q000145:classification / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009361:Neoplasm Invasiveness; D011237:Predictive Value of Tests; D011379:Prognosis; D011446:Prospective Studies; D013997:Time Factors
chemical_list: D014408:Biomarkers, Tumor