The papilloma is a rare benign entity  . The Solitary respiratory papilloma (SRP) is an uncommon pathologic condition of the lower respiratory tract, with less than 60 cases reported in the literature  . It accounts for 0.38% of all pulmonary tumors. Although the precise etiology of respiratory papillomas remains unknown, the general consensus is that the majority are due to infection caused by the human papilloma virus (HPV). If papillomas of the upper airways, frequently referred to as juvenile laryngotracheal papillomatosis, are more frequent in childhood, the SRP are more common in adult population. Papillomas are normally classified into three categories: multiple papillomas, inflammatory polyps, and solitary papillomas   .
Malignant transformation is rare but has been reported. The rate of occurrence of carcinoma from a papilloma is 7.8%  and is not unusual in patients who smoke or who have received irradiation or chemotherapy   . We report a case of solitary endobronchial papilloma mimicking a neoplastic lesion diagnosed by surgical resection.
2. Reported Case
A 39-year-old man, smoker, with no past history, was addressed to our institution for exploration of a cough evolving since six months. There was no history of hemoptysis, weight loss, night sweats, or change in appetite. The physical examination revealed a temperature of 37.6˚C, a respiratory rate of 18 breaths/min, a heart rate of 80 beats/min, a blood pressure of 120/70 mmHg, and a room air oxygen saturation of 96%. A chest examination was normal. A complete blood count, erythrocyte sedimentation rate, liver function test, and Creactive protein were within normal limits. The chest-X-ray revealed alveolar opacity in the right Fowler. We indicated antibiotic treatment based on the combination of amoxicillin and clavulanic acid for a duration of 14 days. Investigations of tuberculosis infection by direct examination were negative in sputum as well as cultures. The evolution was marked by persistence of cough and the imaging opacity. Hence, neoplastic lesion was suspected since the patient was smoker. The chest CT scan showed an endobronchial tissular mass in the intermediate trunk, an unaerated collapse of the middle lobe with an excavated parenchymatous condensation of the right fowler associated with right mediastinal nodes (Figure 1). Flexible bronchoscopy revealed a swollen endobronchial lesion completely obstructing the orifice of the intermediate trunk (Figure 2). Cytology and bronchial biopsies at this level were negative for malignant cells. But the fear of lung cancer conducted us to indicate a surgical resection. Therefore, the patient was operated on by postero-lateral thoracotomy for diagnostic and therapeutic purposes. He underwent a Right lower lobectomy. Pathologic study of the surgical piece showed a polypoid bronchial mucosa, lined by a hyperplastic, papillomatous and acanthosic epithelium without signs of malignancy suggestive of squamous cell papilloma (Figure 3). The Otorhinolaryngologic examination did not demonstrate associated laryngeal papilloma. Human Papilloma Virus (HPV) serology was negative. The evolution is marked by the clinical improvement of the patient. A follow-up CT scan realized after six months didn’t show a recurrence of the tumor.
The solitary pulmonary papilloma category of tumors is relatively unusual. It is
Figure 1. CT Scan showed an endobronchial tissue bud in the intermediate trunk with an excavated parenchymatous condensation of the lower right lobe.
Figure 2. Flexible bronchoscopy revealed a swollen endobronchial lesion completely obstructing the orifice of the intermediate trunk.
Figure 3. Endobronchial papilloma with polypoid bronchial mucosa (a), lined by a metaplastic, papillomatous and acanthosic epithelium, without signs of malignancy (b) (HEx40).
commonly found in genitalia or oral cavity but it is very unusual to be found in the airways as in our patient. Solitary endobronchial papilloma is a rare form representing only 0.5% of all types of papilloma and 0.3% of all lung tumors  . Papillomas of the lung are relatively uncommon but it must be considered in the differential diagnosis of any benign or malignant tumor. It is usually classified into three categories: squamous cell papilloma, glandular papilloma, and mixed (squamous cell and glandular papilloma). Malignant transformation is rare. It is a rare pathology that occurs commonly in middle-aged adult with a male predominance and a frequent association with smoking. The role of HPV in the genesis of this tumor remains controversial. It would have a role in the pathogenesis of the squamous variant but not in the others  . The main complication of this pathology is its malignant transformation, hence the importance of surgical excision. In fact, the rate of occurrence of carcinoma from a papilloma is 7.8%  . In fact, the HPV seems to play a pathogenetic role in some squamous cell papillomas. So, in the benign multiple squamous papillomas of the larynx, trachea, and bronchi, HPV types 6 and 11 were detected using in situ hybridization. Infections with HPV, serotypes 16 or 18, are related with malignant transformation in squamous papillomas  . Therefore, the most important apprehension for the pathologist is to distinguish this benign tumor from malignant tumors, principally intraoperatively, since the misdiagnosis of adenocarcinoma, will almost certainly quick unnecessary surgical treatment. Also, it should be noted that the complete lesion should be submitted for lasting histological evaluation to definitively exclude malignant tumor.
The particularity of our case is first, the clinical presentation since it is a central papilloma which comes to clinical attention due to bronchial obstruction, consequent recurrent pneumonia mimicking a neoplastic lesion essentially in smoker patient. In any case, pathologists may more commonly meet such tumors on frozen section. It should be noted that the total lesion should be submitted for lasting histologic evaluation to definitively exclude malignancy. In second time, the location of papilloma is unusual, since it’s commonly laryngeal. This endobronchial location can simulate a lung cancer particularly in smoker men.
Conflicts of Interest
The authors declare no conflicts of interest regarding the publication of this paper.