Baylor University Medical Center Proceedings July 2017 - 322

Primary mucoepidermoid carcinoma of the lung with
prominent clear cells
David D. Fink, DO, Angela M. Lomas, MD, Anja C. Roden, MD, Prashant C. Shah, MD, and Riyam T. Zreik, MD

Mucoepidermoid carcinoma of the lung is
a rare malignancy of salivary gland-type
origin. We report a case of a 21-year-old
man with a right mainstem bronchus mass
composed predominantly of clear cells.
This case represents a rare primary pulmonary low-grade mucoepidermoid carcinoma positive for MAML2 rearrangement
by fluorescence in situ hybridization with
a prominent clear cell component.

Figure 1 (a) Axial and (b) coronal CT scans of the chest demonstrate a 2.5 cm mass (arrow) within the right main-

rimary pulmonary mucoepi- stem bronchus. The tumor was 0.5 cm from the carina and originated from the lateral aspect of the right mainstem
dermoid carcinoma (PMEC) bronchus with suspected invasion into the right upper lobe bronchus.
is a rare malignant neoplasm
representing 0.1% to 0.2% of all primary pulmonary
the biopsy was diagnosed as non-small cell carcinoma with
carcinomas (1-5). It typically arises in the minor salivary glandclear cell features.
type epithelium of the large central airways (2-5). Occasionally,
Eight months following initial presentation, a right-sided
mucoepidermoid carcinoma (MEC) demonstrates prominent
thoracotomy and sleeve right upper lobectomy were performed.
cytoplasmic clearing (6-10), and on biopsy, the presence of
Gross examination revealed a 2.3 × 2.2 × 1.6 cm well-delineated
these clear cells can pose a diagnostic challenge for pathologists.
mass protruding into the bronchial lumen. Microscopic examination (Figure 2) showed a mass situated in the submucosa
We present a case of PMEC with prominent clear cells.
of the bronchial wall without invasion into the lung parenCASE DESCRIPTION
chyma. In addition to the dominant population of clear cells,
A 21-year-old man presented to his primary care physician
the tumor had foci of gland formation with mucin, squamoid
with a persistent cough producing blood-tinged sputum. The
cells, and intermediate cells. There was no increased mitotic
initial chest x-ray was unremarkable but over the next 3 months
activity or keratinization, but scattered calciﬁcations were apthe patient's cough continued to worsen, progressing to moderparent. Fluorescence in situ hybridization (FISH) was positive
ate hemoptysis. A computed tomography (CT) scan of the chest
for MAML2 rearrangement and negative for EWSR1 rearrangerevealed a 2.5 cm mass within the right mainstem bronchus
ment (Figure 3). The microscopic features and ancillary tests
(Figure 1). Rigid bronchoscopy with biopsy of the mass was
supported the diagnosis of low-grade PMEC.
performed. The hematoxylin and eosin-stained sections of the
The patient tolerated the lobectomy well and was discharged
biopsy yielded a neoplasm composed of large epithelioid cells
without complications or adjuvant therapy. At 15 months
with clear cytoplasm and round-to-oval nuclei with inconspicuous nucleoli. By immunohistochemistry, the tumor cells were
From the Departments of Pathology (Fink, Zreik) and Surgery (Shah), Scott &
positive for pan keratin, EMA, CK7, and vimentin. The tumor
White Medical Center, Temple, Texas; Texas A&M College of Medicine, Temple,
cells were negative for PAX8, CD10, RCC, CAIX, HMB45,
Texas (Lomas); and the Department of Laboratory Medicine and Pathology, Mayo
TTF1, S100, CDX2, inhibin, OCT4, p40, p63, CK5/6, CK20,
Clinic, Rochester, Minnesota (Roden).
calponin, chromogranin, and synaptophysin. EGFR polymerase
Corresponding author: Riyam T. Zreik, MD, Scott & White Medical Center, 2401
chain reaction (PCR) revealed a mutation in exon 18. Based on
S. 31st Street, Temple, TX 76508 (e-mail: Riyam.Zreik@BSWHealth.org; Twitter
handle: @RiyamZreikMD).
the available biopsy material and following expert consultation,
322

Proc (Bayl Univ Med Cent) 2017;30(3):322-324

Table of Contents for the Digital Edition of Baylor University Medical Center Proceedings July 2017