[Nasopharyngeal carcinoma with non-squamous immunophenotype: a clinicopathological analysis of 23 cases]

Objective: To investigate the pathological subtypes and clinicopathological characteristics of the non-squamous immunophenotype nasopharyngeal carcinoma (NSNPC). Methods: The clinicopathological features of the non-squamous immunophenotype nasopharyngeal carcinoma diagnosed between 2011 and 2019 at the First Affiliated Hospital of Zhengzhou University were analyzed using hematoxylin and eosin staining, immunohistochemistry, in situ hybridization, transmission electron microscopy and PCR gene rearrangement. Follow-up data were also collected. Results: There were 14 males and 9 females with a median age of 46 years (ranging from 16 to 76 years) with an average age of 45 years. Microscopically, patterns were similar to the classic nasopharyngeal carcinoma. Immunohistochemistry showed that most NSNPC cases expressed low molecular weight keratin (CK8/18, CK8 and CKL) and expressed pathway proteins in a low level (EGFR, PI3K, p-AKT and p-mTOR), which had significant difference from classic nasopharyngeal carcinoma group (P<0.05). Other proteins including CK5/6, CKpan, CK7, Syn, CD56, CgA, SOX-10, AKT, mTOR, Notch, STAT3 and p-STAT3 showed no statistical difference between the two groups. Pathogen detection showed that EBER was positive (18/23, 78.3%) and HPV positive(2/23, 8.7%)which were HPV35 and HPV38. The cancer suppressor gene BLU was highly expressed in NSNPC; RASSF1 and Rbms3 were less expressed in NSNPC, in line with classic NPC. As a whole, NSNPC was characterized by ultrastructures of low-differentiated squamous cell carcinoma. Compared with classic nasopharyngeal carcinoma, NSNPC had a lower recurrence rate and earlier clinical stage(P<0.05),but there was no significant correlation with age, sex, distant metastasis and death (P>0.05). Conclusions: The histological morphology, etiology and gene changes of NSNPC are similar to those of classical nasopharyngeal carcinoma and ultrastructural findings show that NSNPC still belongs to undifferentiated type in non-keratinized squamous cell carcinoma. The malignant degree of NSNPC is low and the prognosis is good.