Abstract | November 10, 2020
An Unusual Case of Epithelial-Myoepithelial Carcinoma of The Kidney: Primary vs. Metastasis? A Diagnostic Dilemma.
- Prevalence of epithelial-myoepithelial carcinoma in the general population.
- Management of Epithelial-myoepithelial carcinoma.
- Possibility of remote metastatic disease.
Introduction: Epithelial-myoepithelial carcinoma (EMC) is a rare low-grade malignant biphasic tumour that typically arises from the salivary glands, representing less than 1% of salivary gland tumours. It predominantly affects the parotid gland with very few reported cases of distant metastasis. So far, only one reported case of a primary EMC-like renal tumour was found on literature review. We report an extremely rare case of a right kidney epithelial-myoepithelial carcinoma in a patient with a history of parotidectomy for a parotid gland tumour over 30 years prior to presentation. The question remains; is this a new variant of a primary renal malignancy or a rare late renal metastasis of a formerly resected parotid gland tumour?
Case Presentation: This is the case of a 62-year-old Caucasian female former smoker with a history of right parotidectomy for a “reportedly benign” tumor over 30 years prior, admitted at our hospital for ischemic bowel and found to have an incidental solid mass arising from the lower pole of the right kidney measuring ~5.6 cm on contrast-enhanced CT scan. No other suspicious lesions or lymph nodes were identified. The patient was initially evaluated by Urology and required to follow-up outpatient after treatment of ischemic bowel. On re-evaluation three weeks later, the mass was noted to have increased in size by ~2cm on repeat CT scan. Patient underwent a radical right nephrectomy. Pathology results were consistent with epithelial-myoepithelial carcinoma concerning for possible metastasis from a salivary gland tumor. PET CT scan post nephrectomy showed no evidence of regional lymphadenopathy or metastatic disease.
Working Diagnosis: Based on an extensive literature review, only one case of EMC-like renal tumour showing a perivascular pseudorosette-like pattern has been reported. EMC and variants have not yet been integrated among known forms of renal cell carcinoma (RCC). In this case, the solitary and solid nature of the kidney neoplasm, as well as its rapid increase in size, raises concern for a primary renal malignancy as opposed to a metastasis. Also, our patient’s parotid tumour resected over 30 years prior was “reportedly benign” with no available documentation for confirmation. Could a “reportedly benign” or “supposedly malignant” parotid tumour resected over 30 years prior metastasize to the kidney as a solid solitary mass? The findings of no metastatic lesion or regional lymphadenopathy on PET CT scan makes the possibility of a kidney metastasis unlikely. Interestingly, if considered primary; this will be the second reported case of primary EMC-like renal tumour and if considered metastatic; this will be an extremely rare late renal metastasis of a remotely resected parotid gland tumour. This case highlights an extremely rare malignancy presenting in the unique setting of a remote tumour resection with questionable correlation.
Management/ Follow-up: Patient is currently status post nephrectomy and pathology reports from the specimen revealed epithelial-myoepithelial carcinoma. Patient at this time is in remission with no evidence of active disease with repeat imaging studies. Patient continues to follow up with a local oncologist.