Retrograde differential diagnosis of carcinoma and pleomorphic adenoma of ectopic salivary gland tissue

Introduction: Differential diagnosis of malignant neoplasms in the neck region presents considerable difficulties from the viewpoint of detecting a primary organ-confined tumor and a non-organ-confined primary lesion. It is particularly difficult to detect when enlarged regional metastatic lymph nodes are located virtually on the border with the primary tumor localization. In tumors of the salivary glands, even modern capabilities of radiological and morphological diagnostics do not always allow clear differentiation of organ specificity, categories of benignity or malignancy , as well as distinguishing a primary tumor from a metastatic process.

Case description: In a patient with obvious clinical signs of nodular thyroid gland lesion after initial referral to the outpatient clinic, a malignant process was cytologically excluded. However, during additional examination, tumor pathology of the upper third of the neck was detected, which did not confirm its organ specificity to the major salivary glands and regional lymph nodes according to combined data from modern radiological imaging methods. The results of cytological diagnostics of several tumor-like formations on the neck contributed to radical treatment in the setting of a head and neck surgical oncology department, with planned histological and immunohistochemical investigation. The morphologically confirmed malignant origin from salivary gland tissue without organ specificity yielded varying histological reports. In the absence of disease recurrence , given contradictory morphological findings, a review of histological slides and immunohistochemical investigation of the tumor was conducted at a reference center. The review confirmed the presence of a pleomorphic adenoma of aberrant salivary glands in the variant of retrograde differential diagnosis.

Conclusion: A clinical observation is presented in which only the results of a control immunohistochemical investigation allowed formulation of a final clinicopathological diagnosis of pleomorphic adenoma of the ectopic salivary gland with a multicentric growth pattern in the variant of retrograde differential diagnosis with different forms of carcinoma.