Carcinoma ex basal cell adenoma of the parotid gland: A report of an extremely rare case

Basal cell adenoma and basal cell adenocarcinoma of the parotid gland: clinical findings and surgical outcomes in a single-institution study

BACKGROUND

Basal cell adenoma (BCA) is a rare benign tumor within the salivary glands. Basal cell adenocarcinoma (BCAC), the malignant counterpart of BCA, is also an exceedingly rare tumor with very limited clinical studies conducted. This study aims to investigate the clinical characteristics, demographics, and surgical outcomes of patients diagnosed with BCA and BCAC within the parotid gland.

METHODS

A retrospective analysis from May 2003 to August 2023 was performed for all patients undergoing parotidectomy for masses. Retrospective data on gender, age, tumor characteristics, and outcomes were collected. Surgical approaches, including negative margin attainment, capsule removal, and histological diagnosis, were also detailed.

RESULTS

The study included 1268 patients who underwent parotidectomy, resulting in 81 cases of BCA and 7 cases of BCAC. BCA patients, with a mean age of 55.1 years, showed diverse age distribution and predominantly presented in the 50s. In BCAC cases, seven female patients exhibited a predominant location in the deep lobes. FNA revealed BCAC in three out of seven cases, and subsequent parotidectomy was performed, resulting in no observed recurrences or metastases.

CONCLUSION

This study reports the largest number of BCA cases from a single institution and provides comprehensive insights into the demographics, tumor characteristics, and clinical outcomes of both BCA and BCAC. Although further research should be conducted, based on clinical follow-up results, appropriately including the capsule in the tumor excision indicates favorable outcomes, especially when the tumor size is not large.

A Rare Case of Recurrent Carcinoma Ex Basal Cell Adenoma of the Parotid Gland

Basal cell adenoma is encountered in the salivary glands, particularly the parotid gland; however, malignant transformation is rare, and recurrence is much rarer. We report the case of a 60-year-old man who had experienced a slow-growing mass in the parotid gland, which was suspected to be pleomorphic adenoma. Radiological and cytological examination suggested an atypical lesion in the left parotid. The final diagnosis reached on the excised specimen was that of a basal cell adenocarcinoma ex adenoma with close margins. The patient presented with a recurrence after two years. Routine histopathological examination with careful examination by the pathologist is essential for proper management of such rare malignant lesions, and recurrence is a possibility. A complete excision of the tumor with tumor-free margins from the beginning is suggested.

Intracapsular carcinoma ex basal cell adenoma of the parotid gland

Malignant transformation of basal cell adenoma is extremely rare. We report the case of a 63-year-old Chinese woman, who had noticed a slowing growing mass in her right parotid gland with slight pain for 1 month. Based on physical and ultrasound examinations, a diagnosis of benign salivary gland tumour was made before the surgery. A frozen biopsy was performed, and the diagnosis was basal cell adenoma, with the tumour cells infiltrating the capsule. Routine histopathological examination was performed after the surgery, and a final diagnosis of intracapsular basal cell adenocarcinoma ex basal cell adenoma was made. The patient received a further total parotidectomy and recovered well without any evidence of facial nerve palsy. This case suggests that during frozen biopsy, adequate sectioning including the capsule should be made. With regard to the treatment, we suggest a complete excision of the tumour with tumour-free margins, without any additional auxiliary therapy.

An Unusual Hybrid Salivary Gland Tumor: Molecular Analysis Informs the Potential Pathogenesis of This Rare Neoplasm

Background

The presence of two or more tumor entities growing in adjacent locations within the salivary gland is very rare, and pathologic studies on such lesions are limited, particularly those with molecular information. Since the clinical history and imaging studies are usually nonspecific, accurate diagnosis and clinical management largely depend on a thorough histological examination.

Methods and Results

We describe a 71-year-old man with an unusual case of hybrid salivary gland tumor composed of mucoepidermoid carcinoma and basal cell adenoma. Molecular analysis revealed differing driver genetic alterations in each component.

Conclusions

Hybrid salivary gland tumors are rare, and their pathogenesis is controversial. The combination of mucoepidermoid carcinoma and basal cell adenoma has not been previously described. While malignant transformation of adenoma to carcinoma seems plausible, gene sequencing was more suggestive of their independent derivation. Key to appropriate surgical management is identifying the more aggressive component, ideally at the time of intraoperative consultation.