Acta Med. Okayama, 2024
Vol. 78, No. 4, pp. 331‑335
CopyrightⒸ 2024 by Okayama University Medical School.

Case Report

http://escholarship.lib.okayama-u.ac.jp/amo/

A Rare Subglottic Pleomorphic Adenoma: Magnetic Resonance Findings
Chieko Furukawaa＊, Tomoyasu Tachibanaa, Tetsuji Nobuhisab, Yuichiro Kaniec,
Yoji Wanid, Jun-Ya Matsumotoa, Akifumi Kariyaa, Asuka Satoa,
Iichiro Ishikawab, Yuto Naoie, and Mizuo Andoe
Departments of aOtolaryngology Head and Neck Surgery, bSurgery, cRadiology, and dPathology,Japanese Red Cross Society Himeji Hospital, Himeji, Hyogo 670-8540, Japan,eDepartment of Otolaryngology Head and Neck Surgery, Okayama University Graduate School of Medicine,Dentistry and Pharmaceutical Sciences, Okayama 700-8558, JapanNo previous study has published magnetic resonance imaging (MRI) findings for a subglottic pleomorphicadenoma. Here, we describe the case of a 62-year-old man with a subglottic pleomorphic adenoma.
Endoscopic findings revealed a smooth-surfaced tumor arising from the subglottic posterior wall. MRI
revealed the lesion as an isointense region on T1-weighted images, which was homogeneously enhanced. Thislesion showed a heterogeneously hyperintense region on T2-weighted images. Diffusion-weighted imaging(DWI) showed slightly high intensity in the same area, with a normal or only slightly high apparent diffusion
coefficient (ADC). Laryngomicrosurgery was performed for transoral excision of the subglottic tumor, resulting in a postsurgical diagnosis of pleomorphic adenoma.
Key words: subglottis, pleomorphic adenoma, MRI, transoral surgeryPleomorphic adenomas are benign tumors thatoccur in the major or minor salivary glands. In
the larynx, the glands are simple, tubular, and usuallypurely mucous, or large, branched, seromucous tubular-alveolar [1]. Pleomorphic adenomas are known tooccur in the laryngeal regions; however, few reports ofpleomorphic adenomas affecting the subglottic region
have been published [2-6]. Moreover, no cases of subglottic pleomorphic adenomas evaluated using magnetic resonance imaging (MRI) have been reported. In
this study, we report a rare case of a subglottic pleomorphic adenoma evaluated using MRI.

Case ReportMagnetic resonance scanning protocol.

In thisReceived December 28, 2023 ; accepted March 26, 2024.
Corresponding author. Phone : +81-79-294-2251; Fax : +81-79-296-4050
E-mail : pknp1481@gmail.com (C. Furukawa)＊

case, we performed an MRI using a 3-T MR scanner(Achieva ; Philips Medical Systems, Best, TheNetherlands) with a head-neck coil. The imaging
sequences were as follows:(a) T2-weighted fast spin-echo imaging (T2WI) andfat-suppressed T2WI in the axial plane (repetition time[TR]/echo time [TE], 3,053/90 ms; echo train length,
19; matrix size, 269 × 352; field of view, 23 cm; slicethickness, 3 mm).
(b) T2WI and fat-suppressed T2WI in coronal plane(TR/TE, 3,053/90 ms; echo train length, 19; matrix
size, 268 × 268; field of view, 23 cm; and slice thickness, 4 mm).
(c) T1-weighted fast spin-echo imaging (T1WI) inthe axial plane (TR/TE, 452/5.9 ms; echo train length,
3; matrix size, 235 × 336; field of view, 23 cm; andslice thickness, 3 mm).
Conflict of Interest Disclosures: No potential conflict of interest relevantto this article was reported.

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Acta Med. Okayama Vol. 78, No. 4(d) T1WI in coronal plane (TR/TE, 452/5.9ms;
echo-train length, 3; matrix size, 245 × 352; field ofview, 23 cm; slice thickness, 3 mm).
(e) Diffusion-weighted imaging (DWI) with b-valuesof 0 and 1,000 s/mm2 in the axial plane using spin-echo
type and single-shot echo planar imaging (EPI) sequencesin parallel. (TR/TE, 6,000/76 ms; matrix size,117 × 80; field of view, 23 cm; slice thickness, 3 mm).
(f ) Post-contrast enhanced three-dimensional
fat-suppressed T1WI (Gd-T1WI) in the sagittal plane(TR/TE, 4.7/2.1 ms; matrix size, 177 × 256; field ofview, 23 cm; slice thickness, 0.9 mm). Gadobutrol
was intravenously administered at a dose of 0.1 mmol
per kilogram body weight. Axial and coronal images
were obtained from sagittal images using multiplanarreconstruction (MPR).
A 62-year-old Japanese man underwent preoperative examination for surgical treatment of esophageal
cancer at the Department of Surgery of our institution.
The computed tomography (CT) scan incidentally
revealed abnormal findings in the subglottic region,and the patient was referred to our department for further examination. The patient reported no subjective
symptoms.
Endoscopic findings revealed a smooth-surfaced
tumor arising from the subglottic posterior wall(Fig. 1A). The lesion was confined to the subglottic
region, and mobility of the vocal folds was not affected.
No other abnormalities were observed in the laryngopharyngeal region. Ultrasonography revealed no evidence of cervical lymphadenectomy. Moreover, CTA

revealed an enhanced hemispherical mass at the subglottic posterior wall with no invasion of the surrounding tissue (Fig. 1B). MRI revealed a lesion 13 mm indiameter as an isointense region equal to the surrounding muscle tissue on T1WI, which was homogeneouslyenhanced. This lesion showed a heterogeneously
hyperintense region on T2WI (Fig. 2). In this case,
DWI showed slightly high intensity in the same area,
and an apparent diffusion coefficient (ADC) that wasnormal to slightly high (1.108 × 10-3 mm2/s).
Based on endoscopic and MR imaging findings, abenign submucosal tumor was suspected. Preoperatively,
we explained to the patient the possibility of performinga tracheotomy or external incision if oral intubation ortransoral resection of the subglottic tumor was difficult.
However, an endotracheal tube with an internal diameter of 6.0 mm was inserted successfully. The tube wasthen shifted anteriorly using a Weerda laryngoscope toobtain a subglottic view, which allowed adequate visualization of the subglottic lesion. After the transoral
excision, endoscopy confirmed the absence of residual
lesions in the subglottic region. Histological examination of the excised specimen revealed a tumor consisting of a glandular structure of small round cells,including myoepithelial cells and small cysts (Fig. 3).
The interstitium contained fibrous tissue with vitrification and myxoid stroma, resulting in a postsurgicaldiagnosis of pleomorphic adenoma. One year after
surgical treatment, no signs of recurrence have been
observed on imaging or upon physical examination(Fig. 4).

BFig. 1
Laryngeal and computed tomography (CT) ﬁndings at the initial visit. Endoscopic ﬁndings reveal a smooth-surface tumor arisingfrom the subglottic posterior wall (A). Contrast-enhanced CT reveals an enhanced hemispherical mass in the subglottic posterior wall withno invasion of the surrounding tissue (B), as indicated by the arrow.

Subglottic Pleomorphic Adenoma

August 2024

ABCDE

F333

Fig. 2Magnetic resonance imaging (MRI) ﬁndings of subglottic tumor. MRI displays a lesion 13 mm in diameter as an isointense region
equal to the surrounding muscle tissue on T1-weighted imaging (A) and a hyperintense region on T2-weighted imaging (B). This region ishomogeneously enhanced on T1WI (C, D), as indicated by arrows. DWI shows slightly high intensity (E), and ADC is normal or slightly
high (F).

AB

Fig. 3
Histological ﬁndings of resected specimen (hematoxylin and eosin stain). The tumor consists of a glandular structure of smallround cells, indicating the presence of myoepithelial cells and small cysts. The interstitium contains ﬁbrous tissue with vitriﬁcation andmyxoid stroma (A, × 10; B, × 40).

Discussion
Only five cases of subglottic pleomorphic adenoma
have been reported in the English literature [2-6]. In all
previous cases, lesions were discovered after the onsetof dyspnea, and three patients with subglottic pleomorphic adenoma underwent emergent tracheostomy[3 , 4 , 6]. In this study, a subglottic pleomorphic ade-noma was discovered incidentally during a preoperative
examination for esophageal cancer and was diagnosed
without subjective symptoms. However, in any patientwith chronic respiratory symptoms, the possibility ofstenosis in the subglottic region should be considered.
Observing the subglottic region during laryngoscopy isimportant for routine medical care.
In the present case, the lesion was resected as a334

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Acta Med. Okayama Vol. 78, No. 4

benign subglottic tumor, and histopathological examination revealed a pleomorphic adenoma. Benign
tumors occurring in the subglottic submucosal region
include hemangiomas and neurogenic tumors such as
schwannomas, paragangliomas, neurofibromas, andsolitary fibromas. Hemangiomas and paragangliomas
are vascular lesions that can be easily differentiatedfrom pleomorphic adenomas based on the color of themass [7-9]. In contrast, other neurogenic tumors may
present with a surface-smooth, spherical mass as anendoscopic finding, similar to those of the present case[10-12]. To our knowledge, only five cases of schwannoma, one case of neurofibroma, and one case of solitary fibrous tumor have been reported in the subglottic
region in the English literature [10-16]. Details of ourMRI findings are shown in Table 1. Similar MRI find-A

ings have been reported for these diseases, suggestingthat subglottic pleomorphic adenomas may mimic neurogenic tumors in terms of both local and MRI findings.
MRI findings for the imaging diagnosis of subglottic
pleomorphic adenomas have not previously beenreported. Parotid pleomorphic adenomas commonly
show an isointense or hypointense signal on T1WI, acharacteristic bright hyperintense signal on T2WI, anda high signal on both DWI and ADC [17-19]. In thiscase, the lesion was detected before the patient developed respiratory symptoms, allowing for an MRI evaluation. The lesion had findings characteristic of aparotid pleomorphic adenoma, except for those on
T2WI, which showed a heterogeneously hyperintense
signal. On T2WI, hyperintense areas correspond to anB

Fig. 4
Laryngeal and magnetic resonance imaging ﬁndings 1 year after the surgical treatment. No signs of recurrence are observed on
imaging or endoscopy.

Table 1

MRI ﬁndings of subglottic tumors
MRIAuthor
Murata. T11）
2013

Schwannoma

Takeda. K14）
2003

Pulli RS15）
1997

Neuroﬁbroma
PleomorphicadenomaTanaka13）
1997

Present case

T1WI

T2WI

Contrast-Enhanced

DWI

iso

high

homogeneouslyenhanced-

lowhigh-

-

iso

high

homogeneouslyenhanced

-

iso

high

homogeneouslyenhanced

-

iso

high

homogeneously
enhancedhighSubglottic Pleomorphic Adenoma

August 2024

abundance of myxoid components, whereas
hypointense areas indicate fibrosis [19]. We speculatethat the mixture of fibrous tissue and myxoid stroma inthe present case caused a heterogeneously hyperintense
signal on T2WI. In a previous report on pleomorphic
adenoma originating in the epiglottis, the tumor had
high signal intensity on T2WI, low signal intensity on
T1WI, and low signal intensity on the ADC map [20].
In the context of postoperative management ofesophageal cancer, we decided to excise the subglottic
pleomorphic adenoma transorally, without a neck incision. One patient diagnosed with malignant disease on
preoperative biopsy underwent total laryngectomy,
whereas the other underwent transoral resection orlaryngofissure removal [2-6]. According to previous
reports, tumors with a diameter of 18 mm or less can beremoved transorally [3]. In our case, the laryngoscopeprovided an adequate operative field except for thelower edge of the tumor, and endoscopy confirmed theabsence of residual lesions. No apparent recurrence wasobserved 1 year after surgery. Because sufficient margins were not obtained, continuous monitoring of thepatient for recurrence has been necessary.

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