Lin Shinko K, Cassarino David S
Department of Dermatology, Sunset Medical Center, Kaiser Permanente-Southern California, Los Angeles, CA 90027, USA.
Am J Dermatopathol. 2013 Aug;35(6):e99-e102. doi: 10.1097/DAD.0b013e31827401b5.
An 89-year-old man presented with a clinically cystic 4-mm papule on the left temple. The clinical impression was a benign cyst. Pathologic examination revealed a small, symmetric-appearing, well-circumscribed, dermal-based cystic lesion with markedly atypical-appearing clear to squamoid cells lining the cyst wall, consistent with carcinoma in situ involving the cyst. The cells showed abundant glycogen-containing cytoplasm (confirmed by Periodic acid Schiff stains with and without diastase), consistent with tricholemmal differentiation, and areas of tricholemmal/pilar-type keratinization (without a granular layer), consistent with tricholemmal carcinoma in situ, most likely arising in a tricholemmal/pilar cyst. Ki-67 and p53 immunohistochemical stains were strongly positive (with more than 20% of nuclei staining on Ki-67 and more than 80% on p53) in the cyst-lining cells, further supporting the interpretation of carcinoma in situ. Multiple deeper level sections were examined but did not show any evidence of an associated invasive carcinoma. Tricholemmal (pilar) cysts are common benign adnexal lesions and atypia/dysplasia or carcinoma in situ arising within them is exceedingly rare. Previously, only one case of a tricholemmal cyst with carcinoma in situ has been reported. That case was associated with an atypical fibroxanthoma. We report only the second case of tricholemmal carcinoma in situ, most likely involving a tricholemmal cyst, which was not associated with another tumor or evidence of invasive carcinoma.
一名89岁男性患者，左颞部出现一个临床上呈囊性的4毫米丘疹。临床诊断为良性囊肿。病理检查显示，有一个小的、外观对称、边界清晰、位于真皮层的囊性病变，囊肿壁内衬有明显非典型的透明至鳞状细胞，符合累及囊肿的原位癌。细胞显示含有丰富糖原的细胞质（经有无淀粉酶的过碘酸希夫染色证实），符合毛鞘分化，且有毛鞘/毛型角化区域（无颗粒层），符合毛鞘原位癌，很可能起源于毛鞘/毛囊囊肿。囊肿内衬细胞的Ki-67和p53免疫组化染色呈强阳性（Ki-67染色的细胞核超过20%，p53染色超过80%），进一步支持原位癌的诊断。检查了多个更深层次的切片，但未发现任何相关浸润性癌的证据。毛鞘（毛囊）囊肿是常见的良性附属器病变，其中出现的异型增生/发育异常或原位癌极为罕见。此前，仅报道过一例毛鞘囊肿伴原位癌的病例。该病例与非典型纤维黄色瘤有关。我们报告的是第二例毛鞘原位癌，很可能累及毛鞘囊肿，且与另一肿瘤无关，也无浸润性癌的证据。
