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Diagnosis and clinical relevance of uncommon subtypes of colorectal carcinoma
  1. Raul S Gonzalez
  1. Emory University Hospital, Atlanta, Georgia, USA
  1. Correspondence to Dr Raul S Gonzalez, Emory University Hospital, Atlanta, Georgia, USA; rsgonza{at}

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I read with interest the article by Deshpande et al 1 regarding the immune milieu and the prognosis of micropapillary colorectal carcinoma. Their study found that this uncommon subtype of colorectal carcinoma is not associated with inferior disease-specific survival. Our group reported similar findings several years ago in a stage-matched prognostic comparison,2 even though the subtype has a high rate of lymph node and distant metastasis. Of course, other groups have found this subtype to have a significantly worse prognosis in the colorectum,3 as for micropapillary carcinomas in other sites, so the actual prognostic significance of this entity remains somewhat contentious.

Micropapillary carcinoma is one of more than a dozen subtypes of colorectal carcinoma, most of which are formally recognised by the WHO.4 A few of these are relatively common and/or well known, including mucinous, medullary and signet-ring cell. However, several are encountered in a small percentage of colorectal carcinomas, making them less well-known and therefore less recognisable. Some of these subtypes are reportedly associated with improved or worsened survival3 and therefore deserve attention. This letter will briefly discuss their histological appearance and significance.

Serrated adenocarcinoma is essentially defined by serration of the invasive malignant glands, akin to the morphological appearance of sessile serrated lesion (figure 1A).5 Specific features include eosinophilic cytoplasm, low to moderate nuclear:cytoplasmic ratios, little necrosis and prominent mucin production and/or micropapillary features in some regions of the tumour. A high percentage of these carcinomas metastasise to lymph nodes. Some studies have reported serrated adenocarcinoma as representing up to 15% of colorectal carcinomas, though in my experience they are quite uncommon. This may relate to diagnostic threshold differences; additionally, the WHO does not suggest a percentage cut-off necessary for diagnosis. These cancers often arise from precursor tubular adenomas rather than sessile …

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  • Handling editor Vikram Deshpande.

  • Contributors RG wrote this article.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Competing interests None declared.

  • Provenance and peer review Commissioned; externally peer reviewed.

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