title: MASH1: a useful marker in differentiating pulmonary small cell carcinoma from Merkel cell carcinoma.
abstract: Merkel cell carcinoma is the cutaneous counterpart of small cell carcinoma, and the most important differential diagnosis is cutaneous metastasis of small cell carcinoma of the lung. There have been a handful of studies reporting on the utility of a variety of immunohistochemical markers that distinguish between the two entities. Achaete-scute complex-like 1 (MASH1, ASCL1) is important in the development of the brain and the diffuse neuroendocrine system including pulmonary neuroendocrine cells. A recent study, using a cDNA array, identified Mash1 as one of the best classifier genes to differentiate pulmonary small cell carcinoma from Merkel cell carcinoma. We immunohistochemically applied this finding to the diagnostic setting. A total of 30 cases of Merkel cell carcinoma and 59 cases of small cell carcinoma of the lung were immunostained with anti-MASH1 and TTF-1 antibodies. Of 59 small cell carcinomas, 49 (83%) expressed MASH1 in nuclear staining whereas out of 59 small cell carcinomas, 43 (73%) expressed TTF-1 in nuclear staining. MASH1 was completely negative in all 30 Merkel cell carcinomas whereas TTF-1 expression was seen in 1 of the 30 Merkel cell carcinomas (3%). MASH1 is a useful adjunct marker for differentiating small cell carcinoma of the lung from Merkel cell carcinoma.
authors.affiliation: Department of Pathology, New York University School of Medicine, New York, NY 10016, USA.
authors.forename: Jonathan
authors.initials: J
authors.lastname: Ralston
authors.forename: Luis
authors.initials: L
authors.lastname: Chiriboga
authors.forename: Daisuke
authors.initials: D
authors.lastname: Nonaka
mesh_terms: D051792:Basic Helix-Loop-Helix Proteins / Q000378:metabolism*; D014408:Biomarkers, Tumor / Q000378:metabolism*; D015266:Carcinoma, Merkel Cell / Q000175:diagnosis / Q000378:metabolism; D002467:Cell Nucleus / Q000378:metabolism / Q000473:pathology; D004268:DNA-Binding Proteins / Q000378:metabolism; D003937:Diagnosis, Differential; D019084:Fluorescent Antibody Technique, Indirect; D006801:Humans; D007124:Immunoenzyme Techniques; D008175:Lung Neoplasms / Q000175:diagnosis* / Q000378:metabolism; D011237:Predictive Value of Tests; D012878:Skin Neoplasms / Q000175:diagnosis / Q000378:metabolism; D055752:Small Cell Lung Carcinoma / Q000175:diagnosis* / Q000378:metabolism / Q000556:secondary; D046888:Tissue Array Analysis; D014157:Transcription Factors
chemical_list: D051792:Basic Helix-Loop-Helix Proteins; D014408:Biomarkers, Tumor; D004268:DNA-Binding Proteins; D014157:Transcription Factors; C065500:ASCL1 protein, human; C504003:TTF1 protein, human