Background & objective: The primary nasopharyngeal adenocarcinoma (NPAC) is rare. This study was designed to investigate the clinicopathological characteristics of primary NPAC.
Methods: A series of carcinoma biopsies taken from the nasopharynx of the patients followed at Cancer Center, Sun Yat-sen University were reviewed during 24 years. The clinical data and paraffin blocks of 39 NPAC patients were used for this study. In addition, the clinical manifestations of 177 nasopharyngeal carcinoma (NPC) patients were adopted as control. HE, Alcian blue, and PAS histochemical staining were performed and then the morphology was observed under microscope.
Results: (1) There were 153 NPACs found in 31791 carcinomas of the nasopharynx; thus the hospital-based frequency of NPAC was 0.48% (153/31791). (2) The median age of 39 NPAC patients was 46.0 years old and the age peak was 40-49 age group. (3) Seventeen out of 39 NPAC patients (43.5%) were female. (4) Most of NPAC tumors (23/38) took growth beyond the nasopharyngeal cavity (T3) and/or invasion to the cranial bone and/or cranial nerves (T4). Furthermore, only 7 NPAC patients (7/39, 17.95%) had lymph node metastasis; and on the contrary, there were 136 out of the 177 patients (136/177, 76.84%) with NPC had lymph node(s) metastasis. There was significant difference between these two percentages (17.95% vs. 76.84%, P< 0.01). (5) The 39 NPACs could be classified into 2 categories, namely conventional type (16 cases) and salivary gland type (23 cases). The conventional type could further be graded as low-grade (9 cases) and high-grade (7 cases). The 23 salivary-gland type NPACs consisted of 17 adenoid cystic carcinomas and 6 mucoepidermoid carcinomas. (6)The continuation of neoplastic cells to surface lining epithelium was presented in 7 conventional type adenocarcinomas (including all 5 papillary adenocarcinomas) and 4 mucoepidermoid carcinomas. The transition from the adenoid cystic carcinoma cells to the atypical hyperplastic lesion of the ductal epithelium of minor salivary gland was observed in 2 cases.
Conclusion: The primary NPAC is uncommon. The age distribution of NPACs is not different from that of NPCs. Most patients show significant local invasion, but scarce cervical lymph node metastasis, especially adenoid cystic carcinomas.