Polymorphous low-grade adenocarcinoma in the lung: a case report

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

Primary pulmonary salivary gland-type tumours are rare neoplasms that are thought to arise from seromucinous glands that are located in the submucosa of large airways. These neoplasms have clinical and pathologic features that are distinct from other pulmonary neoplasms. The majority of primary pulmonary salivary gland-type tumours are malignant, with the most common entities being mucoepidermoid carcinoma, adenoid cystic carcinoma, and epithelial-myoepithelial carcinoma. Less commonly seen are myoepithelial carcinoma, hyalinizing clear cell carcinoma, acinic cell carcinoma, secretory carcinoma, salivary duct carcinoma, intraductal carcinoma, and polymorphous adenocarcinoma. Benign salivary gland-type tumours of the lung include pleomorphic adenoma and sialadenoma papilliferum. Morphologic, immunophenotypic, and molecular features of these neoplasms are largely similar to salivary gland tumours elsewhere, and therefore the exclusion of metastatic disease requires clinical and radiologic correlation. However, the differential diagnostic considerations are different in the lung. The distinction of salivary gland-type tumours from their histologic mimics is important for both prognostication and treatment decisions. Overall, salivary gland type-tumours tend to have a more favourable outcome than other pulmonary carcinomas, although high-grade variants exist for many of these tumour types. Recent advances in our understanding of the spectrum of salivary gland-type tumours reported in the lung and their diversity of molecular and immunohistochemical features have helped to refine the classification of these tumours and have highlighted a few differences between salivary gland-type tumours of the lung and those primary to other sites.

Primary salivary gland-type polymorphous adenocarcinoma in the lung: A case report and literature review

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.

Lack of PRKD2 and PRKD3 kinase domain somatic mutations in PRKD1 wild-type classic polymorphous low-grade adenocarcinomas of the salivary gland

AIMS

Polymorphous low-grade adenocarcinoma (PLGA) is the second most common intra-oral salivary gland malignancy. The vast majority of PLGAs harbour a PRKD1 E710D hot-spot somatic mutation or somatic rearrangements of PRKD1, PRKD2 or PRKD3. Given the kinase domain homology among PRKD1, PRKD2 and PRKD3, we sought to define whether PLGAs lacking PRKD1 somatic mutations or PRKD gene family rearrangements would be driven by somatic mutations affecting the kinase domains of PRKD2 or PRKD3.

METHODS AND RESULTS

DNA was extracted from eight microdissected PLGAs lacking PRKD1 somatic mutations or PRKD gene family rearrangements. Samples were thoroughly centrally reviewed, microdissected and subjected to Sanger sequencing of the kinase domains of the PRKD2 and PRKD3 genes. None of the PLGAs lacking PRKD1 somatic mutations or PRKD gene family rearrangements harboured somatic mutations in the kinase domains of the PRKD2 or PRKD3 genes.

CONCLUSION

PLGAs lacking PRKD1 somatic mutations or PRKD gene family rearrangements are unlikely to harbour somatic mutations in the kinase domains of PRKD2 or PRKD3. Further studies are warranted to define the driver genetic events in this subgroup of PLGAs.

Case report of polymorphous low-grade adenocarcinoma in the trachea with metastasis to the right middle lobe bronchus

Polymorphous low-grade adenocarcinoma (PLGA) is a low-grade malignant infiltrative tumor of the minor salivary glands. According to data from PubMed (National Center for Biotechnology), one case of PLGA involving the left main bronchus and one case involving the right main and upper lobar bronchi have previously been reported. Here, we describe the first case of PLGA originating in the trachea with metastasis to the right middle lobe bronchus, all initially misdiagnosed as adenoid cystic carcinoma (ACC). It is particularly important to distinguish this tumor from other types of salivary gland tumors, especially ACC. Complete surgical excision is the curative treatment of choice for PLGA.

Polymorphous low grade adenocarcinoma: literature review and report of lower lip lesion with suspected lung metastasis

Polymorphous low grade adenocarcinoma (PLGA) is an uncommon tumour that affects minor salivary glands mainly. It was known to be clinically benign and histologically polymorphic; sometimes misdiagnosed as pleomorphic adenomas, monomorphic adenomas, malignant pleomorphic adenomas, adenoid cystic carcinomas and adenocarcinoma not otherwise specified. More information about PLGA is cumulating in the current literature with new evidences suggesting that the tumour may not be as indolent as it was previously thought. A thorough understanding of the clinical and histological behaviour of the lesion has serious implications in management. Here, a case of lower lip lesion with suspected lung metastasis is reported to exemplify how the clinical behaviour of the lesion may affect management.

Low-grade papillary adenocarcinoma of the palate: the significance of distinguishing it from polymorphous low-grade adenocarcinoma

Low-grade papillary adenocarcinoma (LGPA) represents a relatively rare histological variant of polymorphous low-grade adenocarcinoma (PLGA). There has been a debate as to whether LGPA is associated with greater aggressive potential compared to PLGA; this is further obfuscated by the fact that diagnostic criteria for LGPA have not been well-defined. We believe that this is the first report of a patient with LGPA who developed metastases to the femur and scalp. We review the published evidence for classifying LGPA as distinct from PLGA. The weight of published data does support the idea that LGPA is oncologically distinct from LGPA. However, as uniform diagnostic criteria are lacking, we suggest a cut-off value of 10% or greater papillary formation as being necessary to separate LGPA from PLGA.

Primary polymorphous low-grade adenocarcinoma of the bronchus: complete tumor removal with bronchoscopic resection

Primary polymorphous low-grade adenocarcinoma (PLGA) is an uncommon malignant tumor arising from the minor salivary glands, but its occurrence as a primary tumor of the tracheobronchial tree is very rare. Herein, we have reported a rare case of endobronchial PLGA in a 56-year-old woman presenting with chronic cough and progressive exertional dyspnea. Chest CT clearly demonstrated an endobronchial tumor obstructing the distal part and bifurcation of the left main bronchus and causing distal atelectasis. She underwent rigid bronchoscope with electrocautery and bronchoscopic resection of the tumor. PLGA was diagnosed histologically. Subsequent left pneumonectomy was performed and showed no evidence of residual tumor.

Primary polymorphous low-grade adenocarcinoma of lung treated by sleeve bronchial resection: a case report

We report a surgical case of primary polymorphous low-grade adenocarcinoma (PLGA) of the minor salivary gland-type of the lung. A PLGA originating from the right upper lobar bronchial inlet was successfully treated by sleeve right upper lobectomy. PLGAs are thought to be indolent tumors that are preferentially localized to the palate, and they affect the minor salivary glands almost exclusively. Until now, two cases of distant metastases to the lung have been reported in the English literature. To the best of our knowledge, only one case of PLGA of minor salivary gland-type of the lung without evidence of a previous oropharyngeal primary tumor has been reported in the English literature. But the case was not a single lesion; it was bilateral tumors accompanied by tumors of the cervical lymph nodes. We report here the first case of a single primary PLGA of the minor salivary gland-type of the lung, which was successfully treated by sleeve bronchial resection of right upper lobe.

Polymorphous adenocarcinoma of the breast. Report of three cases

We report three cases of polymorphous adenocarcinoma (PLA) of the breast in 37-, 55- and 74-year-old women, respectively. The patients have no evidence of previous malignancy. The tumours consist of monotonous cells showing a wide spectrum of growth patterns: solid nests, trabeculae, tubules, cribriform structures, strands and fascicles reminiscent of polymorphous low-grade adenocarcinoma of salivary glands. To our knowledge, PLA has never been reported in the breast; therefore, this tumour should be added to the list of neoplastic lesions of the breasts that have the same features as those of the salivary glands.