Primary salivary gland-type polymorphous adenocarcinoma in the lung

Abstract

Rationale: Polymorphous low-grade adenocarcinoma is a low-risk infiltrative malignant tumor of the salivary glands. However, some of these tumors are more malignant than the low-grade tumors and therefore, according to the most recent recommendation of the World Health Organization, they are renamed as polymorphous adenocarcinomas (PACs). Primary polymorphous low-grade adenocarcinomas/PACs of the lungs are rare. Herein, we report a case of primary PAC of the lung with bronchial cartilage and perineural invasion, and lymph node metastasis.Patient concerns: A 58-year-old man had developed fever half a month prior, without chills or other accompanying symptoms, and the underlying reasons were unknown. His self-measured temperature was up to 39°C, accompanied by cough and expectoration, yellow and thin sputum, and shortness of breath. The patient's general state was normal, and respiratory sounds originating from the right lung were weak. Enhancement computed tomography revealed that the bronchial lumen of the basal segment of the lower lobe of the right lung was narrow; soft tissue density nodules were seen, with a range of approximately 2.4 cm  1.3 cm.Diagnosis: Based on clinical information, morphological features, and immunohistochemistry results, the pathological diagnosis was primary PAC of the lungs.Intervention: Thoracoscopic resection of the middle and lower lobes of the right lung was performed, further extended dissection of the mediastinal lymph nodes was performed.Outcomes: The postoperative course was uneventful.Lessons: Primary PAC of the lung is rare and may cause misdiagnosis. When encountering a lung tumor with diverse tissue structures, uniform cell type and nerve invasion, we should consider the possibility of PAC. Morphological and immunohistochemical features can be useful for diagnosing primary PAC of the lungs.Abbreviations: ACC = adenoid cystic carcinoma, CK = cytokeratin, CT = computed tomography, MEC = mucoepidermoid carcinoma, PAC = polymorphous adenocarcinoma, PLGA = polymorphous low-grade adenocarcinoma, TTF-1 = thyroid transcription factor 1.

Recent developments in the pathology of primary pulmonary salivary gland‐type tumours

“…These tumours are morphologically compatible with conventional polymorphic adenocarcinoma of the head and neck, which is characterized by cytologically uniform cells with scant cytoplasm, infiltrative growth with various architectural patterns (including ‘eddy‐like’ formations), and a propensity for targetoid perineural invasion 76 . Four cases had low‐grade cytology, 30–33 and one case had a greater degree of cytologic atypia and mitotic activity 29 . In the head and neck, these tumours are typically CK7‐ and S100 protein‐positive, with frequent p63 and occasional CD117 immunoreactivity.…”

“…Four cases of primary pulmonary polymorphous adenocarcinoma and one case primary to the trachea have been reported. [29][30][31][32][33] All cases occurred in adults, 53 to 66 years of age.…”

“…76 Four cases had low-grade cytology, [30][31][32][33] and one case had a greater degree of cytologic atypia and mitotic activity. 29 In the head and neck, these tumours are typically CK7-and S100 protein-positive, with frequent p63 and occasional CD117 immunoreactivity. Staining for p40 is usually negative.…”

“…30,31 The latter also distinguishes it from AdCC, as does the tendency for polymorphous adenocarcinoma to have more uniform nuclear features, more diffuse EMA staining, and more intense S100 protein staining than AdCC. 30,31 Two of the pulmonary polymorphous adenocarcinomas had lymph node metastases, 29 and the patient with primary tracheal polymorphous adenocarcinoma had a bronchial metastasis, 33 but long-term follow-up data are lacking. Head and neck polymorphous adenocarcinoma typically has an excellent prognosis.…”

“…The most common types of pulmonary salivary gland-type carcinoma include mucoepidermoid carcinoma (MEC), adenoid cystic carcinoma (AdCC), and epithelial-myoepithelial carcinoma (EMC). 6,8,[10][11][12][13] Case reports and series have also described hyalinizing clear cell carcinoma (HCCC), 4,14,15 acinic cell carcinoma (AciCC), [16][17][18][19] secretory carcinoma, [20][21][22][23] salivary duct carcinoma, [24][25][26] intraductal carcinoma, 27,28 and polymorphous adenocarcinoma [29][30][31][32][33] occurring as primary lung tumours. Benign salivary gland-type tumours reported in the lung include myoepithelial tumours and pleomorphic adenomas.…”