Primary pulmonary hyalinising clear cell carcinoma with mucin production and delayed metastases after 16 years

Abstract

Primary pulmonary salivary gland-type cancers are rare, comprising less than 1% of all lung tumours.1Ishikawa Y. Dacic S. Alvarez-Fernandez E. et al.Salivary gland-type tumours: mucoepidermoid carcinoma.in: Travis W.D. Brambilla E. Burke A.P. Marx A. Nichoson A.G. WHO Classification of Tumours of the Lung, Pleura, Thymus, and Heart. WHO, Lyon2015: 99-100Google Scholar Along with mucoepidermoid carcinoma, adenoid cystic carcinoma, and epithelial-myoepithelial carcinoma, primary pulmonary hyalinising clear cell carcinoma (HCCC) can also arise from the peribronchial glands of the bronchus.2Shah A.A. Mehrad M. Kelting S.M. et al.An uncommon primary lung tumour: hyalinizing clear cell carcinoma, salivary gland-type.Histopathology. 2015; 67: 274-276Crossref Scopus (18) Google Scholar, 3García J.J. Jin L. Jackson S.B. et al.Primary pulmonary hyalinizing clear cell carcinoma of bronchial submucosal gland origin.Hum Pathol. 2015; 46: 471-475Abstract Full Text Full Text PDF PubMed Scopus (33) Google Scholar HCCC is a rare salivary gland tumour that was first described by Milchgrub et al. in 1994.4Milchgrub S. Gnepp D.R. Vuitch F. et al.Hyalinizing clear cell carcinoma of salivary gland.Am J Surg Pathol. 1994; 18: 74-82Crossref PubMed Scopus (202) Google Scholar It most commonly involves the minor salivary glands of the head and neck, especially the palate and oral base.4Milchgrub S. Gnepp D.R. Vuitch F. et al.Hyalinizing clear cell carcinoma of salivary gland.Am J Surg Pathol. 1994; 18: 74-82Crossref PubMed Scopus (202) Google Scholar, 5Albergotti W.G. Bilodeau E.A. Byrd J.K. et al.Hyalinizing clear cell carcinoma of the head and neck: case series and update.Head Neck. 2016; 38: 426-433Crossref Scopus (28) Google Scholar HCCC comprises anastomosing cords or nests of small monomorphic cells with pale eosinophilic or clear cytoplasm in a hyalinised stroma.4Milchgrub S. Gnepp D.R. Vuitch F. et al.Hyalinizing clear cell carcinoma of salivary gland.Am J Surg Pathol. 1994; 18: 74-82Crossref PubMed Scopus (202) Google Scholar, 6Ellis G. Clear cell carcinoma, not otherwise specified.in: Barnes L. Eveson J.W. Reichart P. Sidransky D. Pathology and Genetics of Head and Neck Tumours. WHO Classification of Tumours. WHO, Lyon2005: 227-228Google Scholar The recurrent fusion of the Ewing sarcoma breakpoint region 1 (EWSR1) and activating transcription factor 1 (ATF1) genes is the characteristic molecular change in HCCC that was first identified by Antonescu et al.7Antonescu C.R. Katabi N. Zhang L. et al.EWSR1-ATF1 fusion is a novel and consistent finding in hyalinizing clear-cell carcinoma of salivary gland.Genes Chromosomes Cancer. 2011; 50: 559-570Crossref PubMed Scopus (281) Google Scholar, 8Shah A.A. LeGallo R.D. van Zante A. et al.EWSR1 genetic rearrangements in salivary gland tumors: a specific and very common feature of hyalinizing clear cell carcinoma.Am J Surg Pathol. 2013; 37: 571-578Crossref PubMed Scopus (86) Google Scholar, 9Weinreb I. Hyalinizing clear cell carcinoma of salivary gland: a review and update.Head Neck Pathol. 2013; 7: S20-S29Crossref PubMed Scopus (89) Google Scholar Clinically, HCCC is considered a low-grade malignancy, but delayed recurrence and distant metastases have been reported.5Albergotti W.G. Bilodeau E.A. Byrd J.K. et al.Hyalinizing clear cell carcinoma of the head and neck: case series and update.Head Neck. 2016; 38: 426-433Crossref Scopus (28) Google Scholar, 6Ellis G. Clear cell carcinoma, not otherwise specified.in: Barnes L. Eveson J.W. Reichart P. Sidransky D. Pathology and Genetics of Head and Neck Tumours. WHO Classification of Tumours. WHO, Lyon2005: 227-228Google Scholar Herein, we report another case of primary pulmonary HCCC with mucin production and delayed metastases after 16 years. A 69-year-old man had been diagnosed with lung cancer and underwent a right upper lobe lobectomy in 1999. In 2015, enlarged group 3/4 lymph nodes were incidentally found on a brain perfusion computed tomography (CT) scan. Further chest CT revealed multiple nodules up to 1.5 cm in both lungs and one 3.4 cm lymphadenopathy at the right paratracheal region (group 3/4). He denied symptoms such as cough, haemoptysis, dyspnoea, or weight loss. Wedge resections and group 3/4 lymph node dissection were performed through video-assisted thoracoscopic surgery. Four firm, white tumours measuring up to 1.5 cm in diameter were found in the right lower lobe (Fig. 1A), and enlarged group 3/4 lymph nodes metastasised by a firm, white tumour were observed. At the microscopic level, a total of four well-defined round nodules were identified in resected lung tissues (Fig. 1B). The tumours comprised relatively small-sized, polygonal epithelial cells with round nuclei, indistinct nucleoli, and eosinophilic or clear cytoplasm. The tumour cells formed anastomosing cords or solid nests with highly irregular borders in a fibrotic-to-hyalinised background (Fig. 1C,D). Glandular structures with mucin production confirmed with mucicarmine stain were observed (Fig. 1E), and there was no keratinisation (Fig. 1F). Tumour necrosis was observed. Immunohistochemically, the tumour cells were positive for cytokeratin (AE1/AE3) but negative for p40, p63, TTF-1, napsin A, synaptophysin, chromogranin, S100, smooth muscle actin, PAX8, SOX10, and calretinin. The slides from the original lung tumour resected in 1999 were reviewed, which showed a round bronchial tumour predominantly involving the submucosal layer beneath the intact respiratory epithelium (Fig. 2A). The bronchial tumour showed similar histological features, with the presence of low-grade epithelial cells with either eosinophilic or clear cytoplasm that were arranged in anastomosing cords or irregular nests in a fibrotic-to-hyalinised stroma (Fig. 2B). Glandular structures with mucin production were observed and were positive for mucicarmine stain (Fig. 2C,D). Intracytoplasmic glycogen deposition in tumour cells with clear cytoplasm was demonstrated with periodic acid–Schiff and periodic acid–Schiff-diastase stain (Fig. 2E). EWSR1 FISH confirmed EWSR1 gene rearrangement in both the primary bronchial tumour and the pulmonary metastatic lesions (Fig. 1, Fig. 2F). ATF1 FISH also confirmed ATF1 gene rearrangement in both primary and metastatic tumours. Despite the negativity of p63 immunostaining, the histological and genetic results led to a diagnosis of primary pulmonary hyalinising clear cell carcinoma with delayed lung metastasis after 16 years.Fig. 2Microscopic features of the primary lung tumour. (A) The tumour mainly involves the submucosal layer of the bronchus; (B) mixed clear and eosinophilic cells forming cords and nests in a hyalinised background; (C) glandular structures with mucin production and confirmed by (D) mucicarmine stain; (E) glycogen deposition in clear cells highlighted by periodic acid–Schiff stain; (F) EWSR1 rearrangement confirmed with fluorescence in situ hybridisation (arrows indicate cells with separated red and green signals).View Large Image Figure ViewerDownload (PPT) Including the present case, four primary pulmonary HCCC cases that were previously reported in the English literature are summarised in Table 1.2Shah A.A. Mehrad M. Kelting S.M. et al.An uncommon primary lung tumour: hyalinizing clear cell carcinoma, salivary gland-type.Histopathology. 2015; 67: 274-276Crossref Scopus (18) Google Scholar, 3García J.J. Jin L. Jackson S.B. et al.Primary pulmonary hyalinizing clear cell carcinoma of bronchial submucosal gland origin.Hum Pathol. 2015; 46: 471-475Abstract Full Text Full Text PDF PubMed Scopus (33) Google Scholar All of the previously reported cases were male non-smokers with ages ranging from 32 to 53 years. The tumours presented as endobronchial lesions, and their size ranged from 1.6 to 2.6 cm. HCCC most commonly arises from the minor salivary glands of the oral cavity (palate and tongue) and oropharynx. Other uncommon sites include the parotid gland, nasopharynx, lacrimal gland, nasal cavity, and lungs.5Albergotti W.G. Bilodeau E.A. Byrd J.K. et al.Hyalinizing clear cell carcinoma of the head and neck: case series and update.Head Neck. 2016; 38: 426-433Crossref Scopus (28) Google Scholar HCCC typically comprises cells with clear-to-pale eosinophilic cytoplasm or basaloid cells with scant cytoplasm. The proportion of the characteristic clear cells in HCCC varies, and sometimes only rare clear cells can be observed. Based on molecularly verified cases, mucin production is not uncommon in HCCC.7Antonescu C.R. Katabi N. Zhang L. et al.EWSR1-ATF1 fusion is a novel and consistent finding in hyalinizing clear-cell carcinoma of salivary gland.Genes Chromosomes Cancer. 2011; 50: 559-570Crossref PubMed Scopus (281) Google Scholar, 8Shah A.A. LeGallo R.D. van Zante A. et al.EWSR1 genetic rearrangements in salivary gland tumors: a specific and very common feature of hyalinizing clear cell carcinoma.Am J Surg Pathol. 2013; 37: 571-578Crossref PubMed Scopus (86) Google Scholar, 9Weinreb I. Hyalinizing clear cell carcinoma of salivary gland: a review and update.Head Neck Pathol. 2013; 7: S20-S29Crossref PubMed Scopus (89) Google Scholar Antonescu et al. reported mucin in 10 of 23 (44%) HCCC cases, and its distribution ranged from focal to diffuse.7Antonescu C.R. Katabi N. Zhang L. et al.EWSR1-ATF1 fusion is a novel and consistent finding in hyalinizing clear-cell carcinoma of salivary gland.Genes Chromosomes Cancer. 2011; 50: 559-570Crossref PubMed Scopus (281) Google Scholar Due to the rarity and heterogeneous morphology in HCCC, its diagnosis is difficult, especially when it develops in organs other than the oral cavity. With the recognition of the specific EWSR1 rearrangement in HCCC, difficult cases can now be diagnosed through molecular pathological tests.Table 1Primary pulmonary HCCC reported in the literatureSexAge when the primary tumour resectedSmokingSiteSize, cmMucinEWSR1 rearrangementCase 1 (Shah et al.)2Shah A.A. Mehrad M. Kelting S.M. et al.An uncommon primary lung tumour: hyalinizing clear cell carcinoma, salivary gland-type.Histopathology. 2015; 67: 274-276Crossref Scopus (18) Google ScholarMale32NoBronchus1.8−EWSR1 break apart FISH +Case 2 (Shah et al.)2Shah A.A. Mehrad M. Kelting S.M. et al.An uncommon primary lung tumour: hyalinizing clear cell carcinoma, salivary gland-type.Histopathology. 2015; 67: 274-276Crossref Scopus (18) Google ScholarMale39 (tumour found 4 years before surgery)NoBronchus2.6−EWSR1 break apart FISH +Case 2 (García et al.)3García J.J. Jin L. Jackson S.B. et al.Primary pulmonary hyalinizing clear cell carcinoma of bronchial submucosal gland origin.Hum Pathol. 2015; 46: 471-475Abstract Full Text Full Text PDF PubMed Scopus (33) Google ScholarMale38 (tumour found 4 years before surgery)NoBronchus2.6+EWSR1 break apart FISH +EWSR1-ATF1 RT-PCR +Present caseMale53 (multiple lung metastases 16 years later)NoBronchus1.6+EWSR1 break apart FISH +−, negative; +, positive; HCCC, hyalinising clear cell carcinoma; EWSR1, Ewing sarcoma breakpoint region 1; FISH, fluorescence in situ hybridisation; ATF1, activating transcription factor 1. Open table in a new tab −, negative; +, positive; HCCC, hyalinising clear cell carcinoma; EWSR1, Ewing sarcoma breakpoint region 1; FISH, fluorescence in situ hybridisation; ATF1, activating transcription factor 1. In the lungs, HCCC should be able to be differentiated from mucoepidermoid carcinoma (MEC) and non-small cell carcinoma. HCCC shares similar features with MEC including mucin production, clear cells, and pale eosinophilic tumour cells mimicking the intermediate cells of MEC. The most reliable histological findings are mucous cell-lined cysts in MEC and the anastomosing thin cords and irregular nests in HCCC.8Shah A.A. LeGallo R.D. van Zante A. et al.EWSR1 genetic rearrangements in salivary gland tumors: a specific and very common feature of hyalinizing clear cell carcinoma.Am J Surg Pathol. 2013; 37: 571-578Crossref PubMed Scopus (86) Google Scholar, 9Weinreb I. Hyalinizing clear cell carcinoma of salivary gland: a review and update.Head Neck Pathol. 2013; 7: S20-S29Crossref PubMed Scopus (89) Google Scholar However, these characteristic histological features may not be present in a small biopsy, requiring genetic testing to demonstrate EWSR1 rearrangement in HCCC or MAML2 rearrangement in MEC.10Roden A.C. García J.J. Wehrs R.N. et al.Histopathologic, immunophenotypic and cytogenetic features of pulmonary mucoepidermoid carcinoma.Mod Pathol. 2014; 27: 1479-1488Crossref PubMed Scopus (73) Google Scholar Another differential diagnosis is non-keratinising squamous cell carcinoma since HCCC typically shows diffuse p63 immunoreactivity. HCCC typically shows low-grade cytological features and lacks dysplasia of the overlying squamous epithelium compared with the usual squamous cell carcinoma of the lung. In our case, the presence of glandular structures with mucin and the negativity for p40/p63 made lung adenocarcinoma another differential diagnosis. The anastomosing cords/nests of clear cells in hyalinised stroma, lack of TTF-1/napsin A immunoreactivity, and the unusual location of the bronchial submucosa are important histological features of pulmonary HCCC. In the salivary gland tumours, EWSR1 rearrangement is not restricted to HCCC, as it is also present in clear cell myoepithelial tumours of the salivary glands.11Skálová A. Weinreb I. Hyrcza M. et al.Clear cell myoepithelial carcinoma of salivary glands showing EWSR1 rearrangement: molecular analysis of 94 salivary gland carcinomas with prominent clear cell component.Am J Surg Pathol. 2015; 39: 338-348Crossref PubMed Scopus (100) Google Scholar Since ATF1 FISH probe is not commercially available and the RNA quality of formalin fixed, paraffin embedded tissue blocks may not be good enough to carry out RT-PCR to confirm the specific EWSR1-ATF1 fusion in HCCC, currently most studies use immunohistochemical markers to rule out myoepithelial tumours and EWSR1 FISH alone to demonstrate EWSR1 rearrangement. A correct diagnosis should be based on histological examination, immunohistochemical stain, and genetic testing. Patients with HCCC generally have relatively good prognoses. Albergotti et al. reported that the overall recurrence rate was 19.8%, and the presence of necrosis, positive margins, and lymph node status were risk factors associated with recurrence.5Albergotti W.G. Bilodeau E.A. Byrd J.K. et al.Hyalinizing clear cell carcinoma of the head and neck: case series and update.Head Neck. 2016; 38: 426-433Crossref Scopus (28) Google Scholar Recurrent HCCC with high-grade transformation was reported and characterised by the presence of tumour necrosis, bizarre tumour cells, increased mitoses, as well as atypical mitotic figures.12Jin R. Craddock K.J. Irish J.C. et al.Recurrent hyalinizing clear cell carcinoma of the base of tongue with high-grade transformation and EWSR1 gene rearrangement by FISH.Head Neck Pathol. 2012; 6: 389-394Crossref PubMed Scopus (60) Google Scholar In this case, tumour necrosis was present in lung metastases and group 3/4 lymph nodes, but there was no frankly high-grade cytological change. Patients with HCCC need long-term follow-up due to the risk of delayed local recurrence and metastasis.