Trichoblastic Infundibular Cyst

Abstract

We report 4 cases of an infundibular cyst that histopathologically showed small papillary projections of follicular germinative cells emanating from the basal layer of the cyst wall. Some of these projections branched and formed a reticulated pattern. This cystic lesion is histopathologically distinctive. We propose to designate it as a trichoblastic infundibular cyst because its lining resembles that of an infundibular cyst, yet it has cells that resemble those of the follicular germ in its wall.

Cystic trichoblastoma: A report of two cases with an immunohistochemical study

“…Except for our first report of cystic trichoblastoma, 1 the cases of cystic trichoblastoma or trichoblastic infundibular cyst have exhibited papillary projections of follicular germinative cells from the cyst walls. 2,3 Both of our present cases showed the characteristic projections of a solid aggregation, which were identical to trichoblastoma, in addition to the papillary projections. Furthermore, in both cases, the aggregations of trichoblastoma surrounded the cysts, and some of the aggregations were connected to the cyst walls by a cord-like structure.…”

“…In the reports by Ansai et al . and Juárez et al ., the authors did not immunohistochemically prove the nature of the follicular germinative cells in the papillary projections.…”

“…In the reports by Ansai et al 2 and Ju arez et al, 3 the authors did not immunohistochemically prove the nature of the follicular germinative cells in the papillary projections. The presented results of an immunohistochemical study of both cases clearly demonstrated that the papillary projections in various shapes really had the nature of follicular germinative cells, which expressed PHLDA1, as well as CK15 (clone C8/144B).…”

“…In that case, an infundibular cystic structure with an opening pore radiated strands or lobular aggregations of follicular germinative cells from the cyst wall. 1 Shortly after our report, Ansai et al 2 reported four cases of infundibular cysts associated with radial, papillary projections of follicular germinative cells, and they coined the term "trichoblastic infundibular cyst" for these cases as a distinctive variant of infundibular cysts. Recently, Ju arez et al 3 additionally reported three cases, which were similar to the cases of trichoblastic infundibular cyst.…”

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

“…Ansai et al previously reported four cases of unique keratinous cystic lesions, designated as trichoblastic infundibular cyst (TBIC) . TBIC is a distinct variant of infundibular cyst characterized by papillary projections of epithelial cells with large nuclei from the cyst wall.…”