Keywords
pulmonary epithelial–myoepithelial carcinoma - robotic resection - salivary gland
Introduction
Pulmonary epithelial–myoepithelial carcinoma (P-EMC) is a rare low-grade malignant
neoplasm originating from submucosal bronchial glands in the lung.[1] These tumors are morphologically similar to salivary gland neoplasms, with the presence
of two epithelial layers forming duct-like structures. The inner layer is comprised
of epithelial cells and the outer layer consists of clear myoepithelial cells.[2] The typical presentation of P-EMC is a polypoid endobronchial lesion with a random
distribution in the lung.[3] Treatment with complete surgical excision yields low reoccurrence rates and low
probability of distant metastasis.[3] Moreover, salivary gland tumors of the head and neck region are much more difficult
to resect completely because of their less well-defined margins.[3] Metastasis from the salivary EMC is more common than P-EMC; however, metastases
from EMC are mostly found as multiple pulmonary nodules.[2] This case of the P-EMC was found as a single multilobulated lesion with well-defined
borders and therefore was a strong candidate for robotic lobectomy with successful
outcomes.
Case Presentation
A 78-year-old male with a remote 75-pack-year history of smoking was referred for
surgical evaluation after an annual screening chest computed tomography (CT) scan
revealed a suspicious pulmonary mass. The mass was a multilobulated lesion in the
left lower lobe measuring 1.5 cm × 3.8 cm ([Fig. 1]). On positron emission tomography (PET)/CT, the lesion had a standardized uptake
value (SUV) of 8 with no evidence of metastasis or nodal disease. Subsequent endobronchial
ultrasound and navigational bronchoscopy with fine needle aspiration of the mass demonstrated
atypical epithelial cells. No significantly enlarged lymph nodes were noted and no
nodal sampling was performed at that time.
Fig. 1 Radiologic findings. Chest CT scan without contrast with multilobulated lesion in
the left lower lobe with representative component measuring 1.5 cm × 3.8 cm. There
is an additional nodular lesion in the right upper lobe with a representative component
measuring approximately 2.38 cm × 0.8 cm. CT, computed tomography.
The patient underwent a CT-guided core needle biopsy which demonstrated a salivary
gland-like neoplasm. Given the unusual results of the biopsy and the size and central
location of the tumor, the decision was made to perform a left video-assisted thoracoscopic
surgery (VATS), robot-assisted, left lower lobe lobectomy with lymphadenectomy. The
final pathology revealed a P-EMC ([Fig. 2]). Final tumor size was 5.0 cm × 4.5 cm × 2.5 cm with thirty N1 and N2 lymph nodes
negative for carcinoma. Final pathologic stage of the lesion was T2bN0M0 (stage IIA).
All margins were negative. The patient is currently doing well. No adjuvant therapy
was recommended. Although classified as low-grade neoplasms, these tumors can have
a significant rate of recurrence and distant metastasis. Incomplete resection has
been described to have poorer outcomes.
Fig. 2 Medium power view of hematoxylin and eosin–stained section. Biphasic tumor composed
of epithelial and myoepithelial cells arranged in duct-like structures. Lumen of duct-like
structures contain eosinophilic amorphous material.
Overall in one case series, survival appears better than non-small cell lung carcinoma
(NSCLC). Because of its rarity and unproven malignant potential, the optimal therapy
for P-EMC has not been defined. The differential diagnosis includes pulmonary myoepithelial
carcinoma (MEC) and adenoid cystic carcinoma.[4] Immunohistochemically, this case was positive for cytokeratin (CK)-7, CK5/6, pancytokeratin,
p63, S100, and vimentin. The p63 protein, a member of the p53 gene family, acts as a transcription factor to regulate cell growth and division,
cell differentiation and adhesion, and apoptosis. It is found in the basal cells of
respiratory epithelium and peripheral, flattened cells of bronchial mucous glands.[3]
Discussion
Lung cancer is a leading cause of cancer death worldwide in both men and women. Traditionally,
lung cancer is divided into two types, nonsmall cell lung cancer and small-cell lung
cancer that constitute approximately 85 and 15% of cases, respectively.[5] Due to the novel improvements in the art of gene and protein expression profiling,
the fingerprint of individual lung tumors can now be further elucidated. As a result,
in 2015, the World Health Organization further subcategorized epithelial-type lung
cancer into adenocarcinoma, squamous carcinoma, and neuroendocrine tumors.[4] Based on histology and tumor biology, dozens of even more subcategories exist.
Surgical resection of early-stage disease, specifically pulmonary lobectomy, affords
the best chance of cure. Compared with open lobectomy, video-assisted thoracoscopic
lobectomy was associated with a lower incidence of arrhythmias, blood transfusion,
as well as a shorter length of stay, and chest tube duration.[6]
[7]
[8] Robotic-assisted lobectomy has been introduced over the last decade as an alternative
approach to thoracoscopic lobectomy. In addition to the thoracoscopic advantages,
proponents of the robotic approach argue that it allows for improved lymph node yields
with a potential for improved overall survival.[6]
[8] At our institution, all patients scheduled to undergo lobectomy without obvious
chest wall invasion have begun robotically. We subscribe to the theory that robotic
lobectomy offers the aforementioned advantages, specifically reduced pain, less blood
loss, shorter hospital stays, quicker return to preop functionality, and most importantly
higher lymph node yield. Due to these reasons, we believe that long-term outcomes
of this resection will be improved by choosing this approach.
Conclusion
This is a rare case of P-EMC that is worthy of being reported, as it demonstrates
a unique pathology that should be in the differential for atypical lung masses. To
our knowledge, this is one of few case reports describing a robotic lobectomy performed
for P-EMC. This approach was determined to be safe and therapeutic. Further investigation
should be performed to determine the long-term course of this disease subset and optimal
treatment.
