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Basal cell carcinoma with signet ring cell morphology accumulating the ubiquitinated cytokeratin 5/6
  1. Ayako Watanabe1,
  2. Naoshige Iida2 and
  3. Katsuhiko Enomoto3
  1. 1Department of Plastic and Reconstructive Surgery, Japanese Red Cross Akita Hospital, Akita, Japan
  2. 2Department of Plastic and Reconstructive Surgery, Shonan Fujisawa Tokushukai Byoin, Fujisawa, Kanagawa, Japan
  3. 3Department of Pathology, Japanese Red Cross Akita Hospital, Akita, Japan
  1. Correspondence to Dr Ayako Watanabe; ayako_watanabe{at}


Basal cell carcinoma (BCC) showing signet ring (SR) cell morphology is a very rare variant of BCC. Here, we report BCC with SR cell morphology developed in the right cheek skin of a 79-year-old man. Histopathologic examination showed irregularly shaped islands of basaloid cells with characteristic peripheral palisading. Inside of the cancer islands, many tumour cells showed an enlarged fine granular cytoplasm with the peripherally compressed nuclei, being similar to the SR cell. Immunohistochemical examination revealed dense accumulation of cytokeratin (CK) 5/6 and a faint signal of 34βE12 in SR cells. The reported myoepithelial markers were not detected. Interestingly, ubiquitin, a component of the ubiquitin–proteasome protein degradation system, was co-localised in the SR cells. These suggest, for the first time, that accumulation of the undegraded CK5/6 with ubiquitination results in the SR cell morphology. Our report showed that the aberrant keratin turnover is associated with the SR cell BCC.

  • pathology
  • skin cancer

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  • Contributors AW contributed to conceptualisation, validation, resources, and writing; NI to resources and supervision; KE to validation, investigation and writing.

  • 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 Not commissioned; externally peer reviewed.

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