Fiona Stanley Fremantle Hospitals Group

The use of Thyroid Transcription Factor 1 and Napsin A immunohistochemistry in differentiating primary versus metastatic adenoid cystic carcinoma in the lungRoopaa Jeyathevan1, Andrew Laycock1,2,31Department of Anatomical Pathology, PathWest, Fiona Stanley Hospital, Western Australia, 2The University of Notre Dame, School of Medicine, Fremantle, Western Australia, 3Curtin University, Curtin Medical School, Bentley, Western Australia

fsh.health.wa.gov.au FSHM20190410001

Case 1:A 42 year old woman presented for routine surveillance computed tomography (CT) scan and positron emission topography (PET) scan. She has a past history of right maxillary sinus adenoid cystic carcinoma (T4, N0, M0), initially treated with resection in Thailand and right breast invasive duct carcinoma treated with right mastectomy and radiotherapy in 2016. The CT and PET scan noted two small 3mm and 5mm nodules in the lingula of the left upper lobe in 2017 which was kept under observation. Repeat PET scans in November 2018 showed the two nodules had mild FDG avidity but had increased in size to 6mm and 8mm. The patient remained systemically well. Initial investigation with a CT guided fine needle aspiration (FNA) of the left upper lobe lesion was performed and a follow up lung wedge resection was done. The findings of both are discussed below.

Case 2:An 81 year woman presented to the emergency department with multiple falls and confusion in November 2018. She has a past history of right submandibular gland adenoid cystic carcinoma (ACC), treated initially with resection and radiotherapy in 2006. A local recurrence of ACC in 2014 was treated with wide local excision. During her admission she had a CT chest and abdomen which showed a 25mm left upper lobe lung mass. A CT guided core biopsy of the left upper lobe lesion was performed and the findings are discussed below.

Clinical PresentationFigure 1: FNA left upper lobe lung mass, Case 1, showing cellular smears with basaloid cells surrounding acellular globular material. (A) H&E stain 4x; (B) H&E stain 10x; (C) Diff-Quik stain 20x.

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Figure 2: Cell block prepared from FNA left upper lobe mass, Case 1. (A) H&E stain 10x; (B) Dual TTF-1 (brown nuclear) and CK5 (red cytoplasmic) IHC with luminal cells showing positive TTF-1 staining; (C) Dual p40 (brown nuclear) and napsin A (red cytoplasmic) IHC with luminal cells showing positive napsin A staining.

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Figure 4: Wedge resection of left lingula mass, Case 1. (A) H&E stain 4x; (B) Positive TTF-1 nuclear staining in luminal cells; (C) Positive napsin A cytoplasmic staining in luminal cells.

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Figure 5: Core biopsy of left upper lobe mass, Case 2. (A) H&E stain 4x; (B) Dual TTF-1 (brown nuclear) and CK5 (red cytoplasmic) IHC with luminal cells showing patchy positive TTF-1 staining; (C) Dual p40 (brown nuclear) and napsin A (red cytoplasmic) IHC with luminal cells showing patchy positive napsin A staining.

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Figure 3: Cell block prepared from FNA left upper lobe mass, Case 1. MYB break-apart FISH probe showing split red and green signals (arrows). Image courtesy of Chris Van Vliet and Joanne Peverall, Cytogenetics Department, PathWest QE2.

Case 1:• FNA left upper lobe lung mass produced

highly cellular smears with cohesive and dispersed basaloid cells. They show cribriform architecture with basaloid cells surrounding rounded globules of acellular metachromatic magenta coloured material on Diff-Quik staining (Figure 1). The cell block contained similar material and immunohistochemistry (IHC) shows positive staining for thyroid transcription factor 1 (TTF-1) and napsin A in the luminal component, p40 positive staining in the basaloid component (Figure 2).

• Fluorescence in situ hybridisation (FISH) analysis showed an abnormal signal pattern with disruption of the MYB gene at 6q23.2-q23.2 in 36.5% of nuclei (Figure 3).

• Left lingula lung wedge resection showed two well circumscribed lesions with classical appearance of adenoid cystic carcinoma, showing cribriform architecture. The luminal cells have positive staining for TTF-1 and napsin A (Figure 4).

Case 2:• Left upper lobe lung mass core biopsy showed

an infiltrative lesion comprised of cribriform structures lined by a dual population of luminal and apical cells. The cribriform spaces are filled with basement membrane material. The luminal cells showed positive staining for CD117, S100 and CK5, while the apical cells were positive for p40. The luminal cells showed patchy strong positivity for TTF-1 and napsin A (Figure 5).

• FISH analysis showed an abnormal signal pattern with disruption of the MYB gene at 6q23.2-q23.2 in 32% of nuclei.

Cytological Findings

Discussion

Primary ACC of the lung is a rare malignancy and accounts for 0.04% to 0.2% of all primary lung tumours.1 Adenoid cystic carcinoma (ACC) frequently originates from the salivary glands of the head and neck, and has a propensity for multiple and late distant metastases with the lung being the most commonly involved organ.2 Primary lung ACC shows histomorphological features identical to ACC at other anatomical sites. Hence, it is challenging to distinguish primary lung ACC from metastatic carcinomas to the lung. There are clinical features that can be helpful; such as site of tumour and number of lesions. Primary lung ACC is more likely to arise in a central tracheobronchial location while evidence of multiple lesions and/or peripheral locations are more suggestive of a metastatic source.3 However, neither of these criteria are definitive.

Thyroid transcription factor 1 (TTF-1) is a highly conserved homeodomain-containing transcriptional factor and napsin A is an aspartate protease. Both are expressed in lung tissue and positive immunohistochemical staining for these markers have been sensitive and specific biomarkers in assigning pulmonary site of origin for lung tumours that show positive staining.4 Our two cases show lung masses with classical appearance of ACC in patients with known histories of prior salivary ACC, which suggests metastatic disease. However, both cases show positive staining for TTF-1 (clone SP141, Ventana) and napsin A (clone IP64, Novocastra/Leica).

A number of studies have evaluated the expression of TTF-1 and/or napsin A in primary lung ACCs with surprising results.3,5-7 Three of the four studies have shown no staining for TTF-1 in primary lung ACCs (total n= 36) and one study by Qing et al reported positive TTF-1 staining in 4 out of 12 cases (~30%). In addition, An et al. also looked at expression of TTF-1 and napsin

A in metastatic ACCs which included 10 cases of metastatic ACC to lung, from primary head and neck sites. They demonstrated that 50% of metastatic ACCs to lung showed positive immunostaining for TTF-1 and napsin A. Furthermore, the primary tumours in these cases were negative for TTF-1 and napsin A. It has to be noted that due to the rarity of the disease, overall case numbers are small and different TTF-1 clones and immunostaining protocols were utilised in the reported studies. In particular, the reported TTF-1 clones used in the studies were also different to the SP141 clone (Ventana) we used in our cases.

Overall, the current literature shows that positive expression for TTF-1 and napsin A in primary lung ACC is low (overall expression approximately 8%), with a higher percentage of metastatic ACCs to lung expressing TTF-1 and napsin A. This expression profile is in keeping with our two cases of metastatic ACC to lung.

ACCs have also been reported to contain a tumour-type specific t(6;9)(q22-23;p23-24) translocation, which generates a fusion of the MYB proto-oncogene to the transcription factor NFIB.8 Further studies have shown MYB-NFIB fusion or MYB-translocations in approximately 33-66% of salivary ACCs.9-10 This translocation, however, does not appear specific to salivary gland origins with a study into primary lung ACC reporting MYB rearrangements in 41% of cases.11 Thus, while cytogenetics may be a useful adjunct in diagnosing ACC from other salivary gland neoplasms, they do not appear to differentiate between a primary salivary versus lung origin.

• Primary lung adenoid cystic carcinoma is a rare malignancy.• TTF-1 and napsin A positive immunostaining is more likely to be seen in metastatic, rather than primary

lung ACC, based on the current published literature and as shown in our cases. • MYB translocations appear to be identified in similar proportions of primary lung ACC versus salivary gland

ACC, thus do not aid in differentiating primary and metastatic ACC in the lung.

Conclusions 1. Travis WD, Travis LB, Devesa SS. Lung cancer. Cancer. 1995;75:191-202.2. Spiro RH. Distant metastasis in adenoid cystic carcinoma of salivary origin. Am J Surg. 1997;174(5):495-498.3. Qing S, Zhou K, Liu X, et al. Primary pulmonary adenoid cystic carcinoma: clinicopathological analyses of 12 cases. Int J Clin Exp Pathol. 2015;8(6):7619-7626.4. Ye J, Findeis-Hosey JJ, Yang Q, et al. Combination of napsin A and TTF-1 immunohistochemistry helps in differentiating primary lung adenocarcinoma from metastatic carcinoma in lung. Appl Immunohistochem Mol Morphol. 2011;19(4):313-317.5. Huo Z, Meng Y, Wu H, et al. Adenoid cystic carcinoma of the tracheobronchial tree: clinicopathologic and immunhistochemical studies of 21 cases. Int J Clin Exp Pathol. 2014;7(11):7527-7535.6. Hu M, Hu Y, He J, et al. Primary adenoid cystic carcinoma of the lung: Clinicopathological features, treatment and results. Oncol Lett. 2015;9:1475-1481.7. An J, Park S, Sung SH, et al. Unusual expression of thyroid transcription factor 1 and napsin A in metastatic adenoid cystic carcinoma of extrapulmonary origin in the lung. Am J Clin Pathol. 2014;141(5):712-717.8. Brill LB, Kanner WA, Fehr A, et al. Analysis of MYB expression and MYB-NFIB gene fusions in adenoid cystic carcinoma and other salivary

neoplasms. Mod Pathol. 2011;24:1169-1176.9. Mitani Y, Li J, Rao PH, et al. Comprehensive analysis of the MYB-NFIB gene fusion in salivary adenoid cystic carcinoma: Incidence, variability, and

clinicopathologic significance. Clin Cancer Res. 2010;16(19):4722-4731.10. West RB, Kong c, Clarke N, et al. MYB expression and translocation in adenoid cystic carcinomas and other salivary gland tumours with clinic-

pathologic correlation. Am J Surg Pathol. 2011;35:92-99.11. Roden AC, Greipp PT, Knutson DL, et al. Histopathologic and cytogenetic features of pulmonary adenoid cystic carcinoma. J Thorac Oncol.

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