Keywords
pediatric surgery - myoepithelial carcinoma - pediatric - cancer
Introduction
Epithelial–myoepithelial tumors are rare neoplasms that originate from the salivary
glands and comprise 1% of all primary tumors. Epithelial–myoepithelial carcinoma was
first described in the salivary glands in 1972. The World Health Organization has
classified this carcinoma as a malignant tumor composed of variable proportions of
two cell types that typically form duct-like structures.[1]
[2] These tumors are extremely rare in the lung. They include mucoepidermoid carcinoma,
adenoid cystic carcinoma, acinic cell carcinoma, oncocytoma, epithelial–myoepithelial
carcinoma, benign myoepithelioma, and mixed tumors.[3]
[4]
[5] Primary pulmonary myoepithelial carcinoma is a rare neoplasm that is thought to
arise from the submucosal bronchus. These glands are considered to be a form of minor
salivary glands. Primary pulmonary myoepithelial carcinoma is a relatively lower grade
malignant; however, it shows high rates of distant metastasis. Owing to the low incidence,
there is no guideline regarding the optimal therapeutic strategy.[6] Surgical treatment is the only available therapeutic option. Thus far, only two
pediatric cases have been recorded.[7]
[8] To our knowledge, the present case is the first pediatric case treated with surgery
and radiotherapy.
Case Report
Chest radiography was performed for a 7-year-old girl with persistent cough and fever
who was unresponsive to oral antibiotics and showed loss of volume of left lung sustained
by almost total atelectasis. The patient was then admitted to the pediatric ward to
begin intravenous antibiotic therapy. Serological tests for Chlamydia pneumoniae, Mycoplasma pneumoniae, and QuantiFERON test for tuberculosis were negative. A computed tomography (CT)
scan showed an extended mass that occupied the entire upper lobe with axial dimensions
of 70 × 47 mm and assumed discreet enhancement in all the study phases. The bronchi
for the upper lobe were no longer patent with endobronchial projection affecting the
middle third of the main left bronchus. The mass caused posterior dislocation of the
pulmonary arterial vascular axis and inferior dislocation of the superior pulmonary
vein. Based on the radiological reports, the patient was referred to our pediatric
surgery unit. To better define the characteristics of the lesion, a magnetic resonance
imaging was performed. The pictures confirmed the presence of an expansive pulmonary
lesion with a probable origin from the upper left lobe with transverse diameters of
57 × 45 mm and longitudinal extension of 85 mm. The lesion infiltrated the pulmonary
hilum and invaded the bronchial structures up to the left main bronchus ∼2 cm from
the carina. It appeared adherent to the common trunk of the pulmonary artery and to
the pericardium at the level of the left atrium and ventricle with infiltration of
the superior pulmonary vein. The mass appeared to be surrounded by a thin rim of consolidated
lung parenchyma; therefore, it does not seem to infiltrate the thoracic wall ([Fig. 1]). For a complete diagnostic work-up, positron emission tomography–CT was performed;
the findings showed softened uptake of the tracer at the voluminous expansive formation
that tended to accentuate along the margins. Echocardiography revealed a 7-mm ostium
secundum atrial defect with left to right shunt and deformity of the left ventricular
cavity, with preserved systolic function. The deformity was attributable to the mass.
All the tumor markers were negative. After multidisciplinary evaluation, ultrasonography-guided
transthoracic core needle biopsy (22 Gauge) and bronchoscopic biopsies were performed
to establish the diagnosis. Histopathologic examinations revealed the presence of
medium–small-sized cells neoplasia, ovoid and plasmacytoid, with eosinophilic cytoplasm,
lacking of evident cytological atypia with solid growth or in large nests alternating
with myxoid and dense collagenous stroma. Immunohistochemical reactivity was positive
for cytokeratine (CK) AE1AE3, p63, epithelial membrane antigen (EMA), S100, β-catenin,
SOX10, and terminal deoxynucleotidyl transferase (TDT). The morphological and immunophenotypic
data were more suggestive of myoepithelioma. However, the immunocytochemical expression
of TdT did not exclude the possibility of thymic neoplasm. Fluorescence in situ hybridization
analysis showed the absence of translocation of FUS gene in 16p11, EWS gene in 22q12, and SS18 gene in 18q11.2. The case was discussed among pediatric surgeons, oncologists, and
radiologists who concluded that the nature of the cancer was not sensitive to neoadjuvant
treatment, thus indicating elective radical surgery.
Fig. 1 Preoperative computer tomography showing the tumor.
Surgery
After the performance of sternotomy and opening of the pleura bilaterally, the left
thoracic mass was revealed. The mass infiltrated the entire left lung and was attached
to and infiltrated the pericardium, the left pulmonary artery and veins, as well as
the left bronchus. We proceeded to release the left lower lobe by making selective
distal ligation of the pulmonary arterial and venous vessels and of the left lobar
bronchus. The lobectomy was completed with a mechanical stapler. The lower lobe appeared
infiltrated by the mass at the level of the fissure. After resecting the lingular
lobe, it was necessary to proceed under extracorporeal circulation to isolate the
left pulmonary artery and veins. We isolated the pulmonary artery trunk as well as
tied and dissected the Botallo's duct and the left branch of the pulmonary artery.
The two left pulmonary veins and the main left bronchus were dissected and sutured.
The mass was isolated from the remaining pericardium, from the vagus nerve, and from
the phrenic nerve. Once the left pneumonectomy was completed and hemostasis was achieved,
the interatrial defect was surgically closed, and a temporary pacemaker was implanted.
A thoracic expander of 11 × 6 cm was applied and filled with 100 mL of saline solution.
The expander reservoir connector was placed outside of the chest wall, and the reservoir
was placed in a subcutaneous pocket. A left thoracic drain was placed dorsal to the
expander. The postoperative course was uneventful. The temporary pacemaker was removed
after 5 days, and the drain was removed after 8 days. The expander was gradually filled
up to 200 mL with saline in three different infusions over 3 weeks ([Fig. 2]). The patient was discharged on postoperative day 18. Histopathological analysis
confirmed the presence of primary myoepithelial carcinoma of the lung (PMC-L) that
infiltrated the bronchial wall up to the mucosa, the peribronchial fibroadipose tissue
with vascular perineural–neural invasion, the pulmonary parenchyma, the visceral pleura,
the pericardium, and a peribronchial lymph node with embolic metastasis. In view of
the rarity of this neoplasm, the TREP group (“Rare Tumors in Pediatric Age”) means
rare tumors in pediatric age group was consulted to set up a plan for the follow-up
care. The patient was then subjected to radiotherapy with rapid arc technique on the
left thoracic wall in 34 diaphragmatic thickening fractions, 61.2 Gy in total. At
the 14-month follow-up, the patient was alive and was breathing normally without oxygen
support. Neither recurrence of PMC-L nor metastasis occurred, and no chest deformities
were observed.
Fig. 2 Postoperative imaging.
Discussion
Myoepithelial carcinoma primarily arises from the salivary glands, rarely from the
soft tissue.[9]
[10]
[11]
[12] PMC-L was described for the first time in 1998; therefore, we identified 12 cases
in adult patients and 2 in pediatric patients. Treatment of the primary pulmonary
myoepithelial carcinoma involves complete surgical resection followed by radiotherapy.
In case of metastatic disease, chemotherapy and radiotherapy are the standard treatments,
even if there is insufficient information to define the survival and efficacy of these
treatments. Some reports have shown that this tumor is not sensitive to radiotherapy
and chemotherapy. Recommendations regarding chemotherapy or radiation, either pre-
or postoperatively, are difficult to formulate. Close long-term follow-up of this
patient may help us elucidate the natural history of this rare tumor. There are only
two pediatric case described in the literature. The first patient was affected by
an advanced metastatic disease with the disappearance of pulmonary opacity spontaneously
without any treatment[7]; the second case was a relatively small PMC-L in a 7-year-old boy treated surgically.[8] In our case, the biopsy made it possible to establish the diagnosis. In light of
the clinical picture, disease stage, and available reports, we decided to treat the
disease surgically. One challenge in the case of total pneumonectomy in pediatric
patients is the postpneumonectomy syndrome. In our patient, we opted for the placement
of a saline-filled tissue expander into the pleural space, as reported in previous
experiences to avoid postpneumonectomy syndrome. Postpneumonectomy syndrome occurs
in ∼2% of the patients undergoing pneumonectomy for a variety of lung pathologies.
It involves excessive mediastinal shift and rotation toward the empty hemithorax from
where the patient's diseased lung was previously removed. This results in airway and
esophageal obstruction that may lead to death.[13] In our case, the use of the expander was a better treatment from the radiotherapeutic
point of view, as reported in other conditions wherein the insertion of a spacer has
led to advancements in the field of radiotherapy.[14]
[15]
Conclusion
PMC-L is exceedingly rare. To our knowledge, our case represents the first pediatric
case with surgical treatment of PMC-L that involved the whole lung. Surgery is the
main treatment for operable patients. In our case, surgical excision was successful
and can be expected to be curative.
