title: PAX-5 Positivity in Anaplastic Lymphoma Kinase-Negative Anaplastic Large Cell Lymphoma: A Case Report and Review of Literature.
abstract: Anaplastic lymphoma kinase (ALK)-negative anaplastic large cell lymphoma (ALCL) is a subtype of T-cell lymphomas that may mimic several other malignancies morphologically. With the help of immunohistochemistry, most cases of ALCL can be diagnosed on the basis of expression of T-cell lineage associated antigens. However, aberrations in the expression of immunohistochemical markers pose diagnostic challenges. The morphological and immunophenotypic features of ALCL show considerable overlap with classical Hodgkin lymphoma (CHL), which is a B-cell lymphoma. The 2008 World Health Organization Classification of Tumours of Haematopoietic and Lymphoid Tissues suggests that staining for the B-cell transcription factor, paired box 5 (PAX-5), is helpful in differentiating between them, as it is weakly positive in most CHL and should be negative in ALCL. We report a rare case of ALK-negative ALCL, which was positive for PAX-5 and CD15, mimicking CHL by immunohistochemistry, resulting in a diagnostic dilemma.
authors.affiliation: 1 Tata Medical Center, Kolkata, West Bengal, India.
authors.forename: Indu
authors.initials: I
authors.lastname: Arun
authors.affiliation: 1 Tata Medical Center, Kolkata, West Bengal, India.
authors.forename: Paromita
authors.initials: P
authors.lastname: Roy
authors.affiliation: 1 Tata Medical Center, Kolkata, West Bengal, India.
authors.forename: Neeraj
authors.initials: N
authors.lastname: Arora
authors.affiliation: 1 Tata Medical Center, Kolkata, West Bengal, India.
authors.forename: Saurabh Jayant
authors.initials: SJ
authors.lastname: Bhave
authors.affiliation: 1 Tata Medical Center, Kolkata, West Bengal, India.
authors.forename: Reena
authors.initials: R
authors.lastname: Nair
authors.affiliation: 1 Tata Medical Center, Kolkata, West Bengal, India.
authors.forename: Mammen
authors.initials: M
authors.lastname: Chandy
mesh_terms: D000368:Aged; D000077548:Anaplastic Lymphoma Kinase; D014408:Biomarkers, Tumor / Q000032:analysis*; D003937:Diagnosis, Differential; D005260:Female; D006689:Hodgkin Disease / Q000175:diagnosis / Q000473:pathology; D006801:Humans; D017728:Lymphoma, Large-Cell, Anaplastic / Q000175:diagnosis* / Q000473:pathology*; D051757:PAX5 Transcription Factor / Q000032:analysis / Q000096:biosynthesis*; D020794:Receptor Protein-Tyrosine Kinases
chemical_list: D014408:Biomarkers, Tumor; D051757:PAX5 Transcription Factor; C497281:PAX5 protein, human; C000626173:ALK protein, human; D000077548:Anaplastic Lymphoma Kinase; D020794:Receptor Protein-Tyrosine Kinases
keywords: ALK negative; PAX-5 positivity; anaplastic large cell lymphoma; clonal T-cell receptor gene rearrangement; immunohistochemistry