Background: Primary external auditory canal (EAC) malignancies are very rare with adenoid cystic carcinoma (ACC) representing approximately 5% of these tumors. There is insufficient knowledge of the natural behavior of ACC in EAC. The disease needs early detection and complete treatment because of its tendency to recur, vicinity to sensitive organs and lower response to radiation.
Case presentation: In this case study, we presented a case of young female (37 years old) with right external auditory canal (EAC) mass which was diagnosed as a benign tumor, a postoperative biopsy confirmed it as ACC of the EAC which is a rare case in the literature.
Conclusion: Here, we report a rare case of Adenoid Cystic Carcinoma (ACC) of External Auditory Canal (EAC) in a 37 years old Saudi female. Initial, Clinical and CT findings were suggestive of a benign cystic mass but histopathology examination confirmed that tumor was ACC of EAC. The patient underwent to radical excision of the tumor along the complete excision of superficial and deep part of carotid gland followed by adjuvant radiotherapy. Postsurgical recovery was uneventful with no sign of recurrence until one year of follow up.
Keywords: Adenoid Cystic Carcinoma, External Auditory Canal, Computed tomography (CT), Adjuvant Radiotherapy.
Cancers of the external auditory canal (EAC) are extremely rare tumor with more than 80% being squamous cell carcinomas and adenoid cystic carcinoma (ACC) accounting for approximately 5% of all EAC Faisal D 2016, Safinaz Zainor 2013. Since 1894, only 106 cases of (ACC) involving the (EAC) have been reported in English literature Shao-Cheng Liua, 2012. Although it presents a widespread age distribution, peak incidence predominantly occurs among women, between the 5th and 6th decades of life Waldron CA 2009. It is a slow growing but highly invasive cancer with a high recurrence rate. Lymphatic spread to the local lymph nodes is rare; however, It is not uncommon for distant metastasis, mainly to the lungs, that may occur over the course of many years Dong F 2008.
Earlier diagnosis of these tumors is of utmost importance, in view of the fact that delays in diagnosis may increases the risk of distant metastasis Dong F 2008. The propensity for perineural invasion and tendency for local recurrence are well known in ACC patients Spiro RH 1986. The signs and symptoms of this tumor do not always correlate with the histopathological diagnosis and subsequent clinical behavior of these tumors. Deep incisional biopsies need to be taken because superficial biopsies may frequently miss such a lesion Mohammad Hussham Arshad 2009
Aggressive surgical resection with adjuvant radiotherapy is the standard treatment for local disease control Spiro RH 1986, Bhagat S 2012. However, there is a high risk of repeat local recurrence, because of the rarity of (ACC) of the (EAC), most of the observations drawn from various reports lack detailed comparisons of pathological findings and long-term outcome follow-up Shao-Cheng Liua , 2012.
In this case study, we presented a case of young female with right external auditory canal (EAC) mass which was diagnosed as benign tumor but postoperative biopsy confirmed it as ACC of the EAC which is a rare case in the literature.
A 37-year-old female patient presented to our clinic with right external auditory canal swelling associated with on and off earache with no ear discharges for a duration of 10 years, it had earlier been excised three times at private clinics and histopathology reported as syringoma that was confirmed by our pathologist after reviewing the outside slides. Clinical examination revealed that the mass was occupying the concha and extended to the outer one third of the external auditory canal and causing partial obstruction of the canal (Figure 1). Pure tone audiogram showed a mild conductive hearing loss at high frequency. The CT scan of temporal bone showed a well-defined faintly enhancing mass lesion measuring 8 x 10 x 13 mm which was pedunculated from the posterior wall of the right external auditory canal, with no erosion of bone and no involvement of regional lymph node enlargement (Figure 2 A & B). Our findings were suggestive of a benign etiology such as papilloma or adenoma.
Because the patient had been followed up by hematology for low platelet and hepato-splenomegaly she had chance to do Pet scan as part of her investigations that showed right external auditory canal nodule with mild metabolic activity, likely benign. Hepatosplenomegaly had no evidence of focal or hypermetabolic lesions. Only a single small hypermetabolic left external iliac lymph node with possible reactive or inflammatory changes was observed. Her bone marrow study confirms the diagnosis of Gaucher’s disease. Based on given information the swelling (likely benign), the patient underwent simple surgery for excision of the mass, later histopathological examination revealed adenoid cystic carcinoma.
Microscopically, the tumor was composed of baseloid cells arranged in a cribriform architecture (Figure 3). The tumor infiltrated adjacent adipose tissue, skeletal muscles and very close to the elastic cartilage of the external auditory canal (Figure 4). Frequent perineural invasion was identified in this patient (Figure 5).Immunohistochemistry confirmed the diagnosis that showed strong nuclear staining in the outer baseloid cells (P63 immunohistochemistry) and membranous positivity in the inner ductal cells (CK7 immunohistochemistry) as shown in figure 6 and 7 respectively.
After a thorough review of histopathological and immunochemical findings patient was taken again to the operating room where more radical surgery was done to excise the tumor along with the deep and superficial part of parotid gland to clear margins and the parotid gland is negative for malignancy (Figure 8 & 9), keeping radiotherapy as adjuvant tool. The postoperative course was uneventful and the excision site was well healed with no evidence of recurrence until the last follow up (Figure 10).
Prescription of the dose and technqiues used for the RT administration
Adenoid Cystic Carcinomas (ACC) earlier known as cylindroma seldom arise in EAC, however, ACC is the most common lesion of glandular origin Dong F et al 2008. This case of ACC involving a 37 year old female is apparently the first case of Saudi Arabia. Earlier reports clearly show that female in their forties and fifties are more prone to the AC Waldron CA 1988, Dong F 2008, Choi JY 2003, our case being on the lower side of median age.
The symptoms of our case include swelling of the the right external auditory canal and partial hearing loss. Generally, the common clinical manifestations include Otto rhea, regular pain, hearing loss and bleeding Arshad et al 2009. There was no discharge or bleeding in our case.
The etiology of ACC is not fully understood. ACC appears to arise from the ceremonious glands, sweat glands or ectopic salivary gland tissue Fliss DM 1990. In some cases, the tumor may have arisen in the adjacent parotid salivary gland and secondarily may have extended into the ear canal Szanto PA 1984. In our case that mass was occupying the concha and extended to the outer one-third of the external auditory canal and causing partial obstruction of the canal.
Metastasis to regional lymph nodes and distant sites are well-documented so lungs and regional lymph nodes must also be evaluated with CT for metastasis. Mitul Chaitan Bhatt 2016, Sridhar PS 2006, Degirmeni B 2004, Dong F 2008. Evidence of irregular bone erosion or destruction of the canal wall is indicative of malignancy Mitul Chaitan Bhatt 2016. However, in our study PET scan of patient showed that a faintly enhancing mass lesion was pedunculated from the posterior wall of the right external auditory canal, there was no erosion of bone and no involvement of regional lymph node enlargement. Only a single small hypermetabolic left external iliac lymph node with possible reactive or inflammatory changes was observed. Therefore, our findings were suggestive of a benign etiology such as papilloma or adenoma.
Histologically, our findings showed that tumor cells were composed of baseloid cells arranged in cribriform architecture and were infiltrated to adipose tissues, skeletal muscles and towards elastic cartilage of the external auditory canal and presence of strong nuclear staining in the outer baseloid cells (P63 immunohistochemistry) and membranous positivity in the inner ductal cells (CK7 immunohistochemistry). Our findings were in favor of Fliss DM 1990 and Shao-Cheng Liua 2012. In addition to that, in our patient we observed the frequent perineural invasion which is a classical characteristic and diagnostically helpful feature of adenoid cystic carcinoma Hicks GW 1983, Shao-Cheng Liua 2012. Moreover, according to Nemzek WR 1998, ACC is the second most common tumor associated to perineural invasion after squamous cells carcinoma. These findings confirmed the diagnosis of ACC of the EAC with perineural invasion and involvement of the tympanic portion of the temporal bone Shao-Cheng Liua 2012.
After ACC of EAC confirmation, a radical surgery was done and postoperative radiotherapy was given to our patient in order to reduce local relapses Faisal D 2016. Although data from randomized trials is lacking, most practitioners consider such treatment to be beneficial. Garden AS 1995, Balamucki CJ 2012, Simpson JR 1984, Al though, postoperative radiation seems to improve local control rates, the impact on ACC-specific survival is not clear Oplatek A 2010.
ACC of the EAC is a rare malignant tumor. This tumor has an aggressive behavior characterized by local invasiveness and a metastatic risk of approximately 30%. There is insufficient knowledge of the natural behavior of ACC in EAC. We would like to emphasize the need for early detection of adenoid cystic carcinoma of the external auditory canal and its differentiation from other benign conditions and therefore we encourage other authors to report cases concerning diagnostic and treatment difficulties of this malignancy.