A 77-year-old woman with a rare tonsillar tumor: evidence of a stem cell tumor?

T. Puls,  Mvr. M. Ramael, Mr. M. Ramael, L. Op DeBeeck and J. Meyskens 


Pure squamous cell carcinomas are the most common malignant tumors of the palatine tonsil followed by diffuse large B-cell Non-Hodgkin lymphoma and metastatic depos­its of lung carcinoma, gastric carcinoma, melanoma, renal carcinoma and adenocarcinoma of the colon. Muco-epi­dermoid carcinoma of the palatine tonsil is an extremely rare tumor. A literature search revealed only three cases of muco-epidermoid carcinoma of the palatine tonsil. We describe another case and searched for markers indicating ‘stemcellness’ suggesting the possibility of ‘stem cell tumor’.


Case Description

A 77 year old woman was referred for vague complaints of pharyngeal discomfort without dysphagia. There was no history of tobacco abuse nor alcohol abuse. Clinical investigation revealed a tumour in the right palatine ton­sil with associated oedema of the right tonsillar arch. Ton­sillectomy was performed. After two months the patient underwent right neck dissection for removal of suspi­cious lymph nodes. Post-operative radiotherapy was given (32 Gy). The patient is alive and well after one year follow up without any sign of disseminated disease.



Histopathological examination showed a tonsil (3 × 2.5 × 1.5 cm) that was diffusely infiltrated by a malig­nant epithelial tumor with both squamous and mucinous differentiation suggesting muco-epidermoid carcinoma confirmed by PAS-after diastase stain. One of five lym­phnodes was invaded by muco-epidermoid carcinoma. Immunoreactivity was found for cytokeratin 14 and focally for cytokeratin 7. No immunoreactivity was found for TTF- 1, nor cytokeratin 20 thereby ruling out metastatic origin. Additional immunoreactivity was found for p16 and for stem cell associated markers CD44, CD133 and ALDH-1 but not for CD10. Real time PCR disclosed HPV 16 DNA confirming the immunoreactivity for p16 protein.


Take Home Message/Conclusions

Muco-epidermoid carcinoma of the palatine tonsil is an extremely rare tumor but has to be considered in the dif­ferential diagnosis of tonsillar tumors. Our case might be an example of a ‘stem cell tumor’. There is immunoreac­tivity for several cancer stem cell markers (ALDH, CD44) which can be found in tumorigenic cancer stem cells of muco-epidermoid carcinoma. The oncogenic process is probably initiated by HPV 16 infection.