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A diagnostic pitfall; small cell carcinoma-like features in basaloid squamous cell carcinoma of the esophagus

Esophageal basaloid squamous cell carcinoma may resemble small cell carcinoma biopsy specimens and cause difficulties in pathology diagnosis. We aimed to clarify the clinicopathological significance of small cell carcinoma-like morphologies in basaloid squamous cell carcinoma. Thirty biopsy specimens of esophageal basaloid squamous cell carcinoma were reviewed and compared with 13 matched surgical specimens. Small cell carcinoma-like features, such as diffuse growth, nuclear molding, or nuclear crush artifact, were identified in 80% (24/30) of the biopsies and in 77% (10/13) of the surgery specimens, but in a proportionally much smaller area in the surgical specimens than in the biopsy samples. The presence of a small cell carcinoma-like feature had no impact on patients´ outcome. Immunohistochemically, synaptophysin and chromogranin A were consistently negative, while CD56 was expressed in 42% (10/24) of basaloid squamous cell carcinomas with small cell carcinoma-like features. p16, a highly sensitive marker for small cell carcinoma, was also expressed in 8% (2/24). p40 was expressed in all cases of basaloid squamous cell carcinoma. In conclusion, small cell carcinoma-like features are frequent and conspicuous in biopsies, which are probably caused by exogenous factors such as friction and external pressure that occur in biopsy procedure and in the tumor environment. Small cell carcinoma-like features may lead to a misinterpretation of a true small cell carcinoma, if CD56 is the only neuroendocrine marker expressed. p16 expression may also be detected in basaloid squamous cell carcinoma

p16 in highly malignant esophageal carcinomas: the correlation with clinicopathological factors and human papillomavirus infection

p16 is generally considered to be a surrogate maker of human papillomavirus (HPV) infection and also a predictive marker of favorable clinical outcome of patients with squamous cell carcinoma of the oropharynx. p16 overexpression is also known to be induced by deregulation of RB1 in neuroendocrine carcinomas. In highly malignant esophageal neoplasms, however, the status of p16 has remained largely unknown. We immunolocalized p16 and Rb1 in 82 surgically resected esophageal high-grade squamous cell carcinomas (46 poorly differentiated and 36 basaloid squamous cell carcinomas) and 15 esophageal small-cell carcinomas in order to clarify the clinical and biological significance of p16. p16 immunoreactivity was detected in 7/82 (9%) high-grade squamous cell carcinomas and 15 (100%) small-cell carcinomas. p16 immunoreactivity was significantly associated with Rb1 protein loss in both groups (P < 0.001). HPV was detected in none of the p16-positive cases examined. Clinical outcome of the p16-positive high-grade squamous cell carcinomas was not different from that of the p16-negative counterparts (P = 0.687) but significantly better than those with the small-cell carcinomas (P = 0.023). p16 was therefore considered to be induced through an inactivation of the RB1 signaling pathway and not through HPV infection in highly malignant esophageal neoplasms. Nevertheless, patients' clinical outcome of these neoplasms significantly differs; therefore, small-cell carcinomas have to be carefully differentiated from other neoplasms. In addition, p16 overexpression is not predictive of favorable clinical outcome in high-grade squamous cell carcinomas of the esophagus