Primary Bronchial Acinic Cell Carcinoma: A Case Report and Review of the Literature

1. Abstract Importance: Acinic cell carcinoma (ACC) is araremalignant tumor of the salivary gland and primaryACC of the lung is even rarer. It is mainly treated by surgical excision of the tumor.

Observations: In the current report, the patient was an 8-year- old boy who was admitted to our hospital for primary bronchial ACC with intermittent dyspnea. Imaging examination and elec- tronic fiber laryngoscopy examination revealed a large irregular tissuemassin the right side of the trachea (at about the level of the T1 vertebral body) blocking about 90% of the trachea. Our medical team flexibly used the combined application of lowtemperatureplasmaknifeandendoscopytocompletelyremovethetumor atonce,avoidinggreattraumatothepatient,andthepathological findingsconfirmedthepresenceofACC.Theboyfullyrecovered and has remained healthy since undergoing surgery 2 years ago.

Conclusions and Relevance: This case report drawsattention to the importance of the novel surgical resection technique with

Keywords: Primary Bronchial Acinic Cell Carcinoma; Surgical resection; Endoscopy; Ki67

2. Introduction Aciniccellcarcinoma(ACC)isararemalignanttumorofthesal- ivary gland, which accounts for 1 ~ 3% of salivary gland tumors [1].According to their histological structure,ACC can be divided intomicrocapsuletype,solidtype,papillarycystictypeandacinar type[2].ACCisaneoplasmthatarisesfromterminalductcellsor normal serous cells, and it is mainly treated by surgical excision. When there is no distant metastasis, maximizing tumor resection andassociatedlymphnodedissectionisanimportantmeanstoimprovepatientprognosis[3].Postoperativechemoradiotherapyhas certainclinicalvalueininhibitingtheproliferationofcancercells, especially in patients with risk factors, such as positive margin or lymphnodemetastasis[4].ThemarkerofproliferationKi-67may bethebestpredictorofbiologicalbehaviorinKi-67positivecells. NorecurrenceoccurredifKi-67≤5%andthemajorityofpatients haveapoorprognosiswhenKi-67≥10%[2].PrimaryACCof the lung is even rarer than the one in salivary gland.Although, at present, its pathogenesis remains unclear, Haller et al. proposed that it may be related to the upregulation of NR4A3 [5]. It usually appears as a solitary mass adjacent to the bronchus with few lymphnodemetastasesandisconsideredalow-grademalignancy [6].Generally,pathologicalexaminationisrequiredtoconfirmthe diagnosis. As the tumor is always covered with normal tracheal mucosa tissue, it is difficult to obtain a cytological diagnosis by biopsy of a specimen harvested by routine bronchoscopy brush examination[7].Thetumorsareusuallywelldemarcatedandhave acelltypeconsistentwithprimaryACCoftheheadandneck.The tumors can occur in people of all ages, but they most commonly develop in people aged 30-75 years and the median age is 49.5 years [8].

3. Case Presentation An8-year-oldboypresentedwithaone-monthhistoryofdifficul- ty breathing.The patient had signs of breathing discomfort, withoutvoicehoarsenessandchokingcoughafterdrinkingwater.The patient was healthy and had no relevant history of disease. The patienthadnopersonalorfamilyhistoryofmalignancy.electron- ic fiber laryngoscopy examination revealed a subglottic cervical trachealtumor,whichwaslightredandblockedabout90%ofthe trachea.Laboratoryfindingswerewithinnormallimits,including tumor markers. Enhanced computed tomography (CT) examination and three-dimensional(3D)reconstructionofthetrachearevealedthefollow- ing: on the right side of the trachea (at about the level of the T1 vertebral body), there was a nodular density shadow with clear boundary and irregular shape, about 1.0*1.1*0.8 cm in size. On theenhancedscan,obviousenhancementwasobservedandstenosiswasobservedinthecorrespondingtrachealumenwiththesurroundingfatspaceslightlyblurred.Thepathohistologicalanalysis showed that the size of the tracheal tumor was about 1.0*0.8*0.3 cm. The tumor cells are arranged in alveolar and intercalated ducts. The cytoplasm is eosinophilic and part of it is transparent. The local tumor invaded the fibrous connective tissue outside the trachea cartilage. Immunohistochemistry results were as follows: AAT(-);Actin(-);CK18(+);ER(-);GFAP(-);Ki-67(positive tumorcellsaccountedforabout10%);Mammaglobin(-);P64(-); PR (weak +); S-100 (-); CK7 (+). Special staining results were as follows: PAS (local +) .

4. Treatment, Out come and FollowUp After adequate preoperative preparation, the patient underwent endoscopic resection with a low-temperature plasma knife and tracheostomy on May 21, 2020. The patient received anesthesiaintheanesthesiologydepartmentusingtheTransnasalHum idified Rapid-Insufflation Ventilatory Exchange (THRIVE) technique. During the operation, we first performed a low position tracheos- tomy and inserted a size 5.5 anesthesia endotracheal tube with a StudieshavefoundthattheexpressionoftheKi-67antigenis significantly correlated with the survival of patients with salivary abovetheincision.Wefoundthatthetumorwaslocatedabovethe incision and blocked approximately 95% of the trachea diameter asshowninFig.4AandB.WeusedaMedtroniclowtemperature the PlasmaBlade™ soft tissue dissection device (Medtronic Inc., Minneapolis, MN, USA) to completely remove the tumor along the base of the tumor following the safe boundary, and carbonizedthemucosalwallofthetrachealwalltothetrachealcartilage. After the patient recovered from anesthesia, he was transferred to the pediatric intensive care unit (PICU). On the second day after surgery, the patient was able to eat normally and had no signs of difficulty breathing. So, we replaced the anesthesia endotracheal tube with a balloon with a 7-mm metal tracheal tube under local anesthesia. On the 6th day after the operation, the child was able to eat well, and speak with his usual voice when the tracheal tube wasblockedintermittently.Theelectroniclaryngoscopyexamination showed that the original tumor site on the inner wall of the tracheahealedwell,andtubeblockagewascontinuouslyassessed byaplug.Onthe9thdayaftertheoperation,thepatientrecovered well and the tracheal cannula was removed. On the 12th day after surgery,theneckincisionhealedwellwithoutobviousairleakage, and the patient was given discharge guidance, including postdis- charge precautions, and discharged. The patient returned to the hospital for follow-up examination at one month, three months, six months, one and a half years, and two years after discharge. No recurrence was found, and the growth and development were consistent with that of children of the same age.

5. Discussion Aciniccellcarcinoma(ACC)wasfirstdescribedin1953byFoote and Frazell as an independent salivary gland tumor type [9]. The maletofemaleratiowasabout2:3,mostofwhichoccurredinthe parotid gland and submandibular gland, and rarely in the minor salivarygland.Inadditiontoitsorigininsalivaryglands,primary ACCcanalsoariseinbreast,lung,etc.[10,11],amongwhichprimarylungACCistherarest[12].ThefirstcaseoflungACCinthe worldwasfirstreportedbyFechnerin1972[13].Todate,25cases of primary lung ACC have been reported [8]. ACCisalow-grademalignanttumorofthesalivaryglands,which is more common in the neck gland, especially the parotid gland. The symptoms of the patients lack specificity and are mostly related to the size and location of the tumor as well as the obstruction of the distal bronchus [15,16]. Small lesions may cause no symptoms, while enlarged lesions may cause symptoms relatedto obstructive pneumonia, and patients often seek medical treatmentduetocoughandexpectoration[14].Diagnosisofbronchial ACCisbasedonpathologicalexamination,andsurgicaltreatment should be performed once the diagnosis is made. Most of the patientshaveagoodprognosisduetolowgrademalignancyandfew metastases gland tumor [17]. When the marker index of Ki-67 is ≥10%, patients are prone to recurrence and have a high rate of lymph node metastasis. The positive rate of Ki-67 tumor cells in this patient was about 10%, but there is no sign of recurrence at present, thus requiring further follow up [2]. In conclusion, bronchial ACC isa rare tumor in the chest, and its clinical symptoms and imaging manifestations lack specificity, making it prone to misdiagnosis andmisseddiagnosis[18].Eveninthecaseofnegativefiberbronchoscopy,thepossibilityofthisdiseasecannotberuledout.Ifnecessary,biopsyorsurgicaldiagnosisofthisdiseasecanbeobtained [19,20]. Surgical resection is an effective treatment, and most patients have a good prognosis. The 5-year survival rate report-ed in domestic and foreign literature is ≥ 90%, but even decades after surgical treatment, recurrence or metastasis may still occur. Therefore, long-term follow up is necessary for patients with Ki67 greater than 10%.[3].

6. Conclusion In conclusion, tracheal ACC is a rare malignancy, especially in male children. Our medical team flexibly used the combined applicationoflow-temperatureplasmaknifeandendoscopytocompletely remove the tumor at once, avoiding great trauma to the patient.Accordingtothecurrentfollowupresults,theprognosisis good,providinganewsurgicaloptionforthetreatmentofendotracheal tumors in the future.

7. Acknowledgements This work was supported by the grants from the Medical Science andTechnology Innovation Center, Shandong First Medical University & Shandong Academy of Medical Sciences, the National Natural Science Foundation of China ( #82071013,#82171122), the Shandong Natural Union Fund (#ZR202108050034) and the Taishan Young Expert ScholarsFund (#tsqn201812134).

8. Conflict of Interest Statement The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.

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MingXia and Fenglei Xu. Primary Bronchial Acinic Cell Carcinoma: A Case Report and Review of the Literature. Annals of Clinical and Medical Case Reports 2023