Creytens, David

English

Ghent University Academic Bibliography

Downloadedfromhttps://journals.lww.com/amjdermatopathologybyBhDMf5ePHKav1zEoum1tQfN4a+kJLhEZgbsIHo4XMi0hCywCX1AWnYQp/IlQrHD3tIQ5gQCIeyxf+EjKLterUS/4tHLG5nxGTrjoA5GP9BQ=on01/15/2020Downloadedfromhttps://journals.lww.com/amjdermatopathologybyBhDMf5ePHKav1zEoum1tQfN4a+kJLhEZgbsIHo4XMi0hCywCX1AWnYQp/IlQrHD3tIQ5gQCIeyxf+EjKLterUS/4tHLG5nxGTrjoA5GP9BQ=on01/15/2020LETTERS TO THE EDITORTTF-1 Positivity in Mer-kel Cell Carcinoma: TheChosen Clone MattersTo the Editor:I have read with great interest therecently published article by Hugheset al1 describing a case of a combinedMerkel cell carcinoma associated withBowen disease and squamous cell car-cinoma that demonstrated strong andsigniﬁcant positivity for TTF-1 byimmunohistochemistry, and I wouldlike to make some additional com-ments. The authors used in this casestudy the monoclonal anti-TTF-1 anti-body clone SP141 and did not explorethe possible difference between theSP141 clone (Ventana) and the othermain available anti-TTF-1 antibodyclones, such as 8G7G31 (Dako) andSPT24 (Leica/Novocastra). Moreover,other published cases and case seriesof (combined) MCC with TTF-1 posi-tivity did not mention which type ofTTF-1 clone was used.2–4 However,there is strong evidence in the litera-ture that an important factor inﬂuenc-ing the prevalence of TTF-1expression in tumors is the type ofclone that is used.5,6 This has also beendemonstrated in publications docu-menting TTF-1 immunoreactivity inglial neoplasms,7 schwannomas,8breast carcinomas,6 and colorectal car-cinomas.9 I want to illustrate this mat-ter further with a recent case ofa classical Merkel cell carcinoma,clinically presenting as a rapidly grow-ing, ﬁrm, solitary nodule in the face ofan 82-year-old woman. Histologyshowed a dermal-based lesion com-posed of monotonous small round cellswith ﬁnely granular and dusty chroma-tin, inconspicuous nucleoli, and scantycytoplasm (“small blue round cell”morphology). A membranous and par-anuclear dot-like staining with cyto-keratin 20 was observed. The tumorcells showed diffuse cytoplasmicstaining with the neuroendocrinemarkers chromogranin and synapto-physin. The case was sent to me inconsultation, given the strong expres-sion with the TTF-1 antibody clonesSP141 and SPT24 (Figs. 1A, B). Basedon my ﬁndings in the recent publishedstudy on TTF-1 expression in schwan-nomas,8 I performed an additionalmonoclonal anti-TTF-1 antibody clone8G7G31 (Dako) on this peculiar case,which showed no expression (Fig. 1C).The difference in speciﬁcity accordingto the used anti-TTF-1 antibodiescould be explained by a higher afﬁnityof SP141 and SPT24 clones for TTF-1,which aberrantly expressed with a lowlevel in Merkel cell carcinoma that itcould not be detected by 8G7G31clone. Other potential factors that canexplain the difference include method-ological issues such as antibody dilu-tions, antigen retrieval, and detectionsystems. This case further underscoresthe literature data that the sensitivityand speciﬁcity of TTF-1 staining isdependent on the antibody clone used,and attention should be given on usingdifferent clones of antibody raisedagainst the same protein for diagnosticpurpose.David Creytens, MD, PhDDepartment of Pathology, Ghent Universityand Ghent University HospitalGhent, BelgiumREFERENCES1. Hughes AJ, French M, Ah-Weng A, et al. Dif-fuse and strong TTF-1 positivity in a combinedMerkel cell carcinoma. Am J Dermatopathol.2019. doi:10.1097/DAD.0000000000001432.2. Koba S, Inoue T, Okawa T, et al. Merkel cellcarcinoma with cytokeratin 20-negative andthyroid transcription factor-1-positive immu-nostaining admixed with squamous cell carci-noma. J Dermatol Sci. 2011;64:77–79.3. Ishida M, Okabe H. Merkel cell carcinoma con-current with an unusual immunophenotype. JCutan Pathol. 2013;34:839–843.4. Martin B, Poblet E, Rios JJ, et al. Merkel cellcarcinoma with divergent differentiation: histo-pathological and immunohistochemical study of15 cases with PCR analysis for Merkel cellpolyomavirus. Histopathology. 2013;62:711–722.5. Conner JR, Hornick JL. Metastatic carcinomaof unknown primary: diagnostic approach usingimmunohistochemistry. Adv Anat Pathol. 2015;22:149–167.6. Bisceglia M, Galliani C, Rosai J. TTF-1 expres-sion in breast carcinoma-the chosen clone mat-ters. Am J Surg Pathol. 2011;35:1087–1088.7. Kristensen MH, Nielsen S, Vyberg M. Thyroidtranscription factor-1 in primary CNS tumors.Appl Immunohistochem Mol Morphol. 2011;19:437–443.8. Creytens D, Van Bockstal M, Ferdinande L,et al. Comparison of thyroid transcriptionfactor-1 expression by two monoclonal antibod-ies in schwannomas: the chosen clone matters.Hum Pathol. 2018;76:167–168.9. Penman D, Downie I, Roberts F. Positive im-munostaining for thyroid transcription factor-1in primary and metastatic colonic adenocarci-noma: a note of caution. J Clin Pathol. 2006;59:663–664.The author declares no conﬂicts of interest.Am J Dermatopathol  Volume 00, Number 00, January 2020 www.amjdermatopathology.com | 1Copyright © 2020 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.FIGURE 1. A, Hematoxylin and eosin staining of classical Merkel cell carcinoma (original magnification ·200). B, Strong nuclearTTF-1 positivity (clone SP141; original magnification ·200). C, No TTF-1 reactivity (clone 8G7G31; original magnification ·200).Letters to the Editor Am J Dermatopathol  Volume 00, Number 00, January 20202 | www.amjdermatopathology.com Copyright © 2020 Wolters Kluwer Health, Inc. All rights reserved.Copyright © 2020 Wolters Kluwer Health, Inc. Unauthorized reproduction of this article is prohibited.

TTF-1 positivity in Merkel cell carcinoma : the chosen clone matters

Crossref

https://biblio.ugent.be/publication/8642973/file/8642975

TTF-1 positivity in Merkel cell carcinoma : the chosen clone matters

Abstract

Similar works

Full text

Available Versions

Ghent University Academic Bibliography

Crossref