Introduction: Acinic cell carcinoma is a rare salivary gland tumour generally thought to have a good prognosis. The tumour is composed of malignant cells with acinar features. The histopathology and immunohistochemistry are diagnostic. The usual clinical presentation is an un-fixed, slow growing, unilateral tumour of the salivary gland with good prognosis. Visceral metastasis is rare.
Case: We present a rare case of parotid gland acinic cell carcinoma in a young woman who had had initial regional recurrence after 3 years and then metastases to both ovaries 5 years after initial presentation.

Conclusion: This case represents the first reported case of acinic cell carcinoma metastatic to the ovary. Our case emphasizes the importance of a good clinical history in order to be able to offer the most appropriate therapy, including the correct chemotherapy regimen.

Keywords: Acinic cell carcinoma, Parotid gland, Ovarian metastasis

Acinic cell carcinoma is a rare salivary gland tumour generally thought to have a good prognosis. The tumour is composed of malignant cells with acinar features [1]. The architecture may be a mixture of solid, microcystic and follicular [1]. Individual cells are polygonal with granular, basophillic cytoplasm and round eccentric nuclei [1]. The granules are PAS positive and resistant to digestion by diastase [1]. The tumour cells show low grade features, with few (if any) mitoses, necrosis, or pleomorphism (1). Neural invasion is associated with more aggressive tumours [1]. A subset of tumours may show areas of poor differentiation or dedifferentiation with glandular patterns and areas of necrosis [1]. Immunohistochemical staining with DOG1 and SOX10 can be seen in acinar and intercalated duct cells, but this is non-specific [1]. Of note, acinic cell carcinoma is negative for mammoglobin, which is useful in differentiating it from secretory carcinoma [1]. The usual clinical presentation is an un-fixed, slow growing, unilateral tumour [1]. However, some cases present with multiple or bilateral nodules, a proportion of lesions go on to have distant metastases, and the recurrence rate may be as high as 35% [1].

A 32-year-old parous woman was diagnosed with a left parotid gland tumor (March 2013) and underwent a total parotidectomy. Pathology reported acinar cell carcinoma. Post-operatively she received adjuvant radiation therapy (60 Gy in 30 fractions) to the
surgical bed. She smoked a half pack per day for 15 years. Her family history includes testicular cancer, and her father diagnosed with colon cancer in his 60s.
In August 2016, she developed a left neck mass which was excised, and pathology confirmed the recurrence of acinar cell carcinoma. A CT scan of the neck and chest postoperatively showed no definite signs of metastatic disease.
In March 2017, she underwent a repeat wide local excision for a second recurrence.
The final histopathology reported the deep margin of the surgical resection was positive for recurrent disease, and four lymph nodes removed were negative. Follow up CT scan performed two months later demonstrated interval deterioration with new mediastinal lymphadenopathy and new pleural masses in the right hemithorax. She was then offered palliative radiation therapy (64 Gy in 30 fractions), as part of the disease recurrence was below the level of the previous radiation field. In August 2017 she commenced four cycles of Durvalumab and Tremelimumab as part of the IND 228 clinical trial.
CT scan after 3 cycles of immunotherapy showed the development of a large right sided pleural effusion, requiring thoracentesis; cytology was negative for malignant cells. In December 2017, while the patient was still on immunotherapy, a CT scan of the chest showed progression of the right medial pleural mass. Despite the radiologic evidence of disease progression, symptomatically the patient felt improved. In February 2018 immunotherapy was discontinued due to further radiologic disease progression in the chest.
CT abdomen & pelvis, a new 3.2 x 3.4 cm hyperdense lesion of the left ovary was seen; Repeat imaging in March 2018 demonstrated a new right pararenal nodule, and an increase in size of the left ovarian lesion to 4.9 x 4.5 cm (Figures 1 & 2).
In July 2018 she presented with worsening left pelvic pain and pressure, abdominal bloating and a sensation of incomplete voiding. A pelvic ultrasound done described a large, predominantly solid pelvic mass, measuring 12.7 x 11.6 x 8.8 cm as well as newly developed ascites. Her CA 125 was 122 U/ml. She was referred to Gynecologic Oncology, and after discussion was consented for surgery to rule out a second primary. In September 2018 she underwent a laparotomy, hysterectomy, bilateral salpingo-opherectomy and omental biopsy. Intraoperatively, the uterus and both fallopian tubes appeared normal and there was no peritoneal carcinomatosis noted. The right ovary contained an 8 cm solid mass (Figure 3), and the left ovary contained a 12 cm solid mass (Figure 4). Pathologic review showed both ovaries contained acinic cell carcinoma (Figures 5-7) consistent with her primary salivary gland carcinoma. The immunohistochemistry (IHC) stains (Figures 8 and 9) were carried out for confirmation and tumor tested negative for estrogen and progesterone receptors. Post-operatively the patient is doing well with minimal symptoms.

1. WHO classification of head and neck tumours. 4 ed. France: Lyon : International Agency for Research on Cancer; 2017.
2. Patel NR, Sanghvi S, Khan MN, Husain Q, Baredes S, Eloy JA. Demographic trends and disease-specific survival in salivary acinic cell carcinoma: an analysis of 1129 cases. Laryngoscope. 2014;124(1):172-178.
3. Scherl C, Kato MG, Erkul E, et al. Outcomes and prognostic factors for parotid acinic cell Carcinoma: A National Cancer Database study of 2362 cases. Oral Oncol. 2018;82:53-60.
4. Biron VL, Lentsch EJ, Gerry DR, Bewley AF. Factors influencing survival in acinic cell carcinoma: a retrospective survival analysis of 2061 patients. Head Neck. 2015;37(6):870-877.
5. Geiger JL, Garcia JJ, Price KA. Acinic cell carcinoma of the salivary gland with metastatic spread to the pancreas. Case Rep Oncol. 2014;7(1):195-198.
6. Torous V, Conrad R, Wang H, Lu D. Widely Metastatic Parotid Acinic Cell Carcinoma to Bone and Liver: A Case Report, Review of Literature, and Review of Diagnostic Challenges. Journal of Cytology & Histology. 2014(S4):1.
7. Khelfa Y, Mansour M, Abdel-Aziz Y, Raufi A, Denning K, Lebowicz Y. Relapsed Acinic Cell Carcinoma of the Parotid Gland With Diffuse Distant Metastasis: Case Report With Literature Review. J Investig Med High Impact Case Rep. 2016;4(4):2324709616674742.
8. Sessa S, Ziranu A, Di Giacomo G, Giovanni A, Maccauro G. A rare case of iliac crest metastasis from acinic cell carcinoma of parotid gland. World J Surg Oncol. 2014;12:48.
9. Zook JD, Djurasovic M, Dimar JR 2nd, Carreon LY. Spinal metastasis from acinic cell carcinoma of the parotid gland: a case report. Spine J. 2012;12(8):e7-10.
10. Oliveira LR, Soave DF, Oliveira Da Costa JP, Ribeiro-Silva A. Acinic Cell Carcinoma of Parotid Gland: Report of Three Cases and Literature Review. Revista Portuguesa de Estomatologia, Medicina Dentaria e Cirurgia Maxilofacial. 2010;51(1):5-11.
11. Saleh TA, Hakin KN, Davidson MJ. Metastasis of acinic cell carcinoma of the parotid gland to the contralateral orbit. Arch Ophthalmol. 2003;121(12):1783-1786.
12. Lesniak MS, Tihan T, Olivi A. Solitary central nervous system metastasis from acinic cell carcinoma of the parotid gland. J Otolaryngol. 2002;31(1):38-41.
13. Shaaban H, Modi T, Patel H, Kumar A, Maroules M. Superior vena cava syndrome due to metastasis from acinic cell carcinoma of the parotid gland. Lung India. 2015;32(1):87-88.
14. Longacre TA, O'Hanlan K, Hendrickson MR. Adenoid cystic carcinoma of the submandibular gland with symptomatic ovarian metastases. Int J Gynecol Pathol. 1996;15(4):349-355.
15. Variakojis D, Archer FL, Feldman SA, Moody RA. Rapidly progressing adenoid cystic carcinoma. Arch Otolaryngol. 1970;92(1):90-93.