[Expression of CD56, as a potential diagnostic marker, in small cell carcinoma].

Background & Objective: Small cell carcinoma is a rare malignant disease with high mortality, which is pathologically diagnosed by using routine neuroendocrinal markers, such as neuron-specific enolase (NSE), synaptophysin (SYN), chromogranin A (CgA). This study was to investigate the expression of CD56, a neural cell adhesion molecule (NCAM), in small cell carcinoma tissues, and to explore the possibility of CD56 as a diagnostic marker of small cell carcinoma.

Methods: Eighty samples of small cell carcinoma were collected, including 42 samples of small cell lung carcinoma (with 20 cases of lymph node metastases), 21 samples of small cell esophageal carcinoma, and 17 samples of small cell colorectal carcinoma. Thirty-eight samples of non-small cell lung cancer (with 28 cases of lymph node metastases), including 26 samples of squamous cell carcinoma and 12 samples of adenocarcinoma, were used as control. All samples were detected using markers of CD56, NSE, SYN, CgA, cytokeratin (CK), and epithelial membrane antigen (EMA) immunohistochemically.

Results: Positive rate of CD56 was significantly higher in either small cell lung carcinoma or their metastatic lymph nodes than in either non-small cell lung carcinoma or their metastatic lymph nodes [90.5% (38/42) vs. 7.8% (3/38), 90.0% (18/20) vs. 3.5% (1/28); H=85.731, P<0.001]. Positive rate of CD56 in small cell carcinoma samples (86.3%, 69/80) were significantly higher than those of SYN (78.8%, 63/80), CgA (73.8%, 59/80), EMA (66.3%, 53/80), CK (61.3%, 49/80), and NSE (56.3%, 45/80) (H=38.871, P<0.001). Positive rate of CD56 in small cell lung carcinoma (90.5%, 38/42) was similar to those in small cell esophageal carcinoma (81.0%, 17/21) and small cell colorectal carcinoma (82.4%, 14/17) (H=1.651, P=0.438).

Conclusions: CD56 is highly expressed in either small cell carcinoma or their metastatic lymph nodes without organ-specificity. It could serve as a potential diagnostic marker of small cell carcinoma.