Predictors of distant metastasis in acinic cell carcinoma of the parotid gland

Role of stereotactic radiosurgery for recurrent skull base acinic cell carcinoma: illustrative case

BACKGROUND

Acinic cell carcinomas (AcCCs), rare malignancies of the salivary glands, often recur and metastasize, particularly in the skull base. Conventional radical resection can be invasive for skull base AcCCs adjacent to cranial nerves and major vasculature, and the effectiveness of stereotactic radiosurgery (SRS) as an alternative is not well established.

OBSERVATIONS

This case report details the application of SRS for recurrent skull base AcCCs. A 71-year-old male with a history of resection for a right mandibular AcCC 23 years earlier experienced tumor recurrence involving the right cavernous sinus and nasal cavity. He underwent endoscopic transnasal surgery followed by SRS targeting different tumor locations-the cavernous sinus to the pterygopalatine fossa, maxillary sinus, and clivus-each with a prescribed dose of 20 Gy to the 40% to 50% isodose line. After the first skull base metastasis, additional sessions of localized SRS after endoscopic surgery led to a 12-year survival without sequela.

LESSONS

This is a report indicating that SRS for skull base AcCCs can achieve favorable local control, functional preservation, and long-term survival. SRS may be suitable for skull base AcCC given the lesion's tendency toward multiple local recurrences. Further investigation is needed to validate the treatment's efficacy.

Chaotic transformation of parotid acinic cell carcinoma to metastatic dedifferentiated high-grade pathology - A rare case with clinical and emotional challenge

INTRODUCTION AND IMPORTANCE

Acinic cell carcinoma (AciCC) is a rare entity in which high-grade transformation (HGT), formerly dedifferentiation, is uncommon. This case report presents a rare case of AciCC, with rapid transformation to metastatic high-grade dedifferentiated pathology after initial curative treatment.

CASE PRESENTATION

A 58-year-old woman presented in the medical oncology clinic with a progressive swelling on the right side of her face. Magnetic resonance imaging revealed a 5 × 5 cm lobulated parotid gland lesion, and fine needle aspiration biopsy was consistent with carcinoma. After informed consent, a Modified-Blair incision was given as a standard approach to the right preauricular area under general anaesthesia, and a right superficial parotidectomy with the removal of the tumor and selective lymph node dissection was performed. Histopathology of the resected mass was reported as parotid AciCC. She was given adjuvant radiation therapy. A repeat PET CT scan ten weeks after the completion of her adjuvant radiation treatment showed local disease recurrence as well as multiple pulmonary deposits. A repeat biopsy was reported as DOG-1 positive dedifferentiated (high-grade) acinic cell carcinoma, and she was offered platinum-based palliative systemic chemotherapy.

CLINICAL DISCUSSION

Parotid acinic cell carcinomas with high-grade transformation are rare. This case highlights its critical diagnostic markers, curative and palliative management and long-term follow-up.

CONCLUSION

The transformation of parotid AciCC to high-grade, dedifferentiated pathology is unusual and belligerent. Hence, these tumors need intense treatment with a multimodality approach. Close follow-ups with history and physical examination, along with periodic imaging, should be considered for these patients.

Head and Neck Acinic Cell Carcinoma: A New Grading System Proposal and Diagnostic Utility of NR4A3 Immunohistochemistry

Acinic cell carcinoma (AciCC) is traditionally considered as a low-grade salivary gland carcinoma. However, a subset demonstrates high-grade features with a higher mortality rate and distant metastasis. In this large retrospective study of 117 cases, we aimed to establish a histologic grading scheme for AciCC. Adverse independent prognostic factors identified on the multivariate analysis included older age, tumor necrosis, nuclear anaplasia, lymphovascular invasion, absence of tumor-associated lymphoid stroma, and high American Joint Committee on Cancer (AJCC) pT and pN stages. A 3-tiered grading scheme using 4 pathologic parameters (mitotic index, necrosis, tumor border, and fibrosis at the frankly invasive front) was subsequently applied. Compared with low/intermediate-grade, high-grade AciCC defined as a mitotic index ≥5/10 HPFs and/or necrosis was an independently adverse prognostic factor. The 5-year overall survival was 50% in high-grade AciCCs, and 100% in low-grade or intermediate-grade AciCCs. Compared with low-grade or intermediate-grade AciCC, high-grade tumors were associated with older age, larger tumor size, focal rather than diffuse zymogen granules, solid architecture, infiltrative tumor border, fibrosis at the frankly invasive front, lymphovascular invasion, perineural invasion, positive margin, high pT, and pN stages. NR4A3 was a highly sensitive and specific immunohistochemical stain for diagnosing AciCC with a sensitivity and specificity of 96% and 93%, respectively. In conclusion, although we proposed a 2-tiered grading system for AciCC with high-grade tumors defined by a mitotic count ≥5/10 HPFs and/or necrosis, more studies are needed to assess the prognostic value of intermediate grade. NR4A3 immunohistochemical stain is a useful diagnostic marker for AciCC.

A Rare Case of Brain Metastasis from Dedifferentiated Acinic Cell Carcinoma of the Parotid Gland and Review of the Literature

Acinic cell carcinoma (ACC) is a low or intermediate-grade malignant epithelial neoplasm of the salivary glands that generally shows an indolent behavior. Most cases arise in the major salivary glands, especially the parotid gland. ACC is usually known as a low-grade malignant tumor; however, poorly differentiated and high-grade transformed variants have been reported and may tend to be late recurrence and metastasis. Our case was a 49-year-old woman with a history of a right parotid rapidly growing mass lesion, which was cytologically diagnosed as monomorphic adenoma on fine-needle aspiration (FNA). Finally, the diagnosis of ACC with dedifferentiated components was reported, followed by parotidectomy. After 30 sessions of radiotherapy, she presented with hemifacial paresis. An imaging examination of the brain showed intracranial hemorrhage, and she underwent a craniotomy. We performed histopathological and immunohistochemical (IHC) examinations and diagnosed metastatic ACC with dedifferentiated components. Few ACC cases with dedifferentiated components and with aggressive behavior have been reported in the literature , and to the best of our knowledge, this article is the first English report in Iranian population.

Acinic cell carcinoma of the parotid gland: from pathogenesis to management: a literature review

PURPOSE

Acinic cell carcinoma (ACCs) is uncommon malignant epithelial neoplasm of the salivary glands; the most common presentation is a well-defined painless solid mass. Diagnosis of ACCs is frequently complicated, due to its similarity with benign tumors.

METHODS

A review of the literature available on ACCs was carried out. Studies were sourced from PubMed with searching of relevant headings and sub-headings and cross-referencing.

RESULTS

There are no clear characteristics of ACCs found on CT, MRI and ultrasound imaging. The management of the ACC, a rare malignancy of the parotid gland, is often difficult and controversial. Radical surgery is the best treatment option. The role of radiotherapy remains controversial: the precise indications and oncologic effects of adjuvant radiotherapy in ACC of the parotid gland are not well known. There is insufficient literature regarding the chemotherapy for metastatic ACC.

CONCLUSION

Knowledge about ACC, a rare malignancy of parotid gland, has changed over the past few decades. More clinical randomized works would be needed, both to assess the real effectiveness of radio and chemotherapy and to have an unanimous consensus about their indications.