Department of Dermatology, Shizuoka City Shimizu Hospital, Shizuoka, Japan.
Department of Plastic and Reconstructive Surgery, Tokushima University Graduate School of Medical Science, Tokushima, Japan.
J Cutan Pathol. 2020 May;47(5):481-484. doi: 10.1111/cup.13641. Epub 2020 Jan 9.
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.
毛鞘内囊性腺瘤（TBIC）以前被报道为一种独特的角化囊性病变，其特征为从囊壁发出的滤泡生发细胞样的乳头状突起。在此，我们报告另外 3 例该囊肿，并讨论这一独特实体的发病机制。在所有病例中，单房性囊肿均含有角蛋白，囊壁由鳞状上皮组成。许多索状结构和乳头状突起从囊壁的基底细胞层发出。它们由细胞核大、细胞质稀少的细胞组成，呈外周栅栏状排列。免疫组织化学染色显示，抗细胞角蛋白 15、抗细胞角蛋白 20 和上皮细胞黏附分子抗体均为阴性。因此，这些细胞在形态上类似于滤泡生发细胞或皮脂腺帽，但我们未能通过免疫组织化学证明其分化。囊肿周围为纤维性基质和炎症细胞，提示囊肿曾破裂。我们推测，突起中的细胞可能分化为帽状细胞，而不是滤泡生发细胞，尽管我们无法提供充分的免疫组织化学证据。我们还认为，这些细胞可能是对围绕着内陷囊肿的纤维组织细胞的特殊反应所诱导的。因此，TBIC 应更名为具有独特乳头状突起的内陷囊肿。
