Metastatic minor salivary gland colloid carcinoma in the parotid region after parotidectomy for pleomorphic adenoma: a case report

BACKGROUND: Primary colloid or mucinous carcinoma of the salivary glands is extremely rare. Only a few cases have been reported that originated in the minor salivary glands. an even more exceptional presentation is as a metastatic tumor in the parotid region subsequent to superficial parotidectomy for pleomorphic adenoma. The case presented here posed a diagnostic dilemma that could be resolved only after a thorough reevaluation of the previous cytologic and histologic material and detection of the occult primary tumor in the hypopharynx following an extensive clinical and radiologic workup. CASE: A 75-year-old female underwent fine needle aspiration of the left parotid and was diagnosed as having pleomorphic adenoma. A superficial parotidectomy removed the tumor completely, and the diagnosis was confirmed. Six months following the surgery, the patient developed an enlarged nodular mass in the ipsilateral parotid region, with fine needle aspiration showing colloid (mucinous) adenocarcinoma, which proved to be a metastatic colloid (mucinous) carcinoma on excisional biopsy. The clinical and radiologic workup in search of a primary lesion led to an occult tumor in the left hypopharyngeal mucosa. CONCLUSION: Unusual presentations of rare tumors can cause considerable diagnostic difficulties to both the clinician and cytopathologist. Awareness of these rarities is important to ensure the best patient care and to avoid unnecessary investigative and therapeutic procedures.