Trichoblastic infundibular cyst should be renamed infundibular cyst with unique papillary projections

Kenta Kobayashi, Tomoaki Yokoyama, Yoko Masuda, Ichiro Hashimoto, Shin ichi Ansai

Research output: Contribution to journalArticlepeer-review


Trichoblastic infundibular cyst (TBIC) was previously reported as a unique keratinous cystic lesion, which was characterized by the papillary projections of follicular germinative-like cells emanating from the cyst wall. Here, we report three additional cases of this cyst and discuss the pathogenesis of this unique entity. In all cases, a unilocular cyst contained keratin, and the cyst wall was composed of squamous epithelium. A number of cords and papillary projections emanated from the basal layer of the cyst wall. They were composed of cells with large nuclei and scant cytoplasm arranged in a peripheral palisade. Immunohistochemically, anti-cytokeratin 15, anti-cytokeratin 20, and anti-epithelial cell adhesion molecule antibodies were negative. Thus, these cells resembled follicular germinative cells or sebaceous mantle morphologically, but we failed to prove the differentiation immunohistochemically. The cyst was surrounded by fibrotic stroma and inflammatory cells, suggesting previous rupture of the cyst. We speculate that the cells of the projections possibly differentiate into the mantle rather than follicular germinative cells, even though we could not provide sufficient immunohistochemical evidence. We also suggest that they may be induced by special reaction to fibrohistiocytic stroma surrounding the infundibular cyst. Therefore, TBIC should be renamed infundibular cyst with unique papillary projections.

Original languageEnglish
Pages (from-to)481-484
Number of pages4
JournalJournal of Cutaneous Pathology
Issue number5
Publication statusPublished - 2020 May 1
Externally publishedYes


  • cystic trichoblastoma
  • follicular germinative differentiation
  • infundibular cyst
  • mantle
  • trichoblastic infundibular cyst

ASJC Scopus subject areas

  • Pathology and Forensic Medicine
  • Histology
  • Dermatology


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