ALK+ large B‐cell lymphoma: A rare variant of aggressive large B‐cell lymphoma mimicking carcinoma on cytology specimens

Abstract

Anaplastic lymphoma kinase positive large B-cell lymphoma (ALK+ LBCL) was recognized as a distinct entity by the 2008 WHO classification of lymphomas. Histologically, the tumor cells exhibit either plasmablastic or immunoblastic morphology, with characteristic granular staining for ALK. The purpose of this study is to evaluate the cytologic findings of ALK+ LBCL. The cytologic material obtained by needle biopsy from three cases of ALK+ LBCL was evaluated. All lesions were nodal and the cytologic material analyzed included air-dried and alcohol-fixed slides stained with modified Giemsa and/or HE stains. The following morphologic criteria were assessed: cellularity, cluster characteristics, cell size, cytoplasmic and nuclear characteristics, and background composition. The cytology specimens obtained from the needle biopsies were moderately to highly cellular and composed of a population of large cells with immunoblastic or plasmablastic morphology. Single cells were present in all three cases, but two cases also showed the presence of clusters with acinar and papillary architecture. Multinucleation was noted in all three cases. Amorphous metachromatic background material was noted focally in the modified Giemsa stained slides in all three cases. Immunostains performed on cytology specimens showed cytoplasmic immunoreactivity for ALK, with characteristic granular features. ALK+ LBCL is a rare recently recognized type of lymphoma with unique morphologic and immunophenotypic findings that can mimic epithelial tumors. Recognition of this potential diagnostic pitfall is critical to prevent unnecessary additional work-up and mistreatment.

Anaplastic lymphoma kinase positive large B‐cell lymphoma: Literature review and report of an endoscopic fine needle aspiration case with tigroid backgrounds mimicking seminoma

“…[10][11][12] The cytomorphologic appearance of large cells with admixed background lymphocytes in "tigroid" backgrounds in the air-dried and modified Giemsa stained preparations in our case raised the differential diagnosis of seminoma at the time of ROSE. The available reports of ALK1 LBCL in the cytology literature focus on potential pitfalls of diagnosis such as the possibility of mistakenly diagnosing this disease as a carcinoma secondary to epithelioid morphology with cohesiveness/clustering, pseudo-acinar or pseudo-papillary formations, and abundant cytoplasm.…”

“…The available reports of ALK1 LBCL in the cytology literature focus on potential pitfalls of diagnosis such as the possibility of mistakenly diagnosing this disease as a carcinoma secondary to epithelioid morphology with cohesiveness/clustering, pseudo-acinar or pseudo-papillary formations, and abundant cytoplasm. [10][11][12] The cytomorphologic appearance of large cells with admixed background lymphocytes in "tigroid" backgrounds in the air-dried and modified Giemsa stained preparations in our case raised the differential diagnosis of seminoma at the time of ROSE. [28][29][30] Tigroid backgrounds are classically present in smears and scrape preparations made from seminomatous germ cell tumors and are described as having delicate, blue-gray, frothy background material dispersed in a pattern of interlacing ribbons, felt reminiscent of a tiger's coat pattern.…”

“…[3][4][5][6][7][8][9] Immunohistochemically, the lesional cells in this disease demonstrate strong immunoreactivity for ALK protein, with patterns of staining differing according to translocation partner. [10][11][12] This report focuses on a challenging case in which the combination of clinical presentation and the presence of a tigroid background in modified Giemsa stained FNA smears from splenic hilar lymph nodes suggested an initial differential diagnosis of seminoma. Clathrin (CTLC) and nucleophosmin (NPM) fusions with ALK are perhaps the most commonly encountered translocations in ALK1 non-Hodgkin lymphomas; however, there are several other fusion gene partners for ALK reported in ALK1 LBCLs.…”

“…[2][3][4][5][6][7][8] Very few published manuscripts exist (three to our knowledge) which detail specific cytologic or needle aspiration features of cases of ALK1 LBCL, and there are no previously documented examples of this disease entity encountered by endoscopic ultrasound-guided fine needle aspiration (EUS FNA). [10][11][12] This report focuses on a challenging case in which the combination of clinical presentation and the presence of a tigroid background in modified Giemsa stained FNA smears from splenic hilar lymph nodes suggested an initial differential diagnosis of seminoma.…”

Cytologic perspectives on neoteric B‐cell lymphoproliferative disorders

“…[24][25][26][27][28][29][30][31][32][33] Only a few cases of ALK1 LBCL have been described in the cytology literature with most of these focusing on potential pitfalls in diagnosis, such as the possibility of mistakenly diagnosing this rare disease as carcinoma or seminoma because of epithelioid morphology, cohesion and comparatively abundant cytoplasm ( Figure 3). [34][35][36][37] Immunohistochemically, ALK1 LBCLs show a characteristic pattern of reactivity in which the lesional cells are classically positive for ALK1, plasma cell markers (CD38, CD138, and MUM1), and epithelial membrane antigen (EMA). The cells are typically CD30 non-reactive (negative); although, focal areas of positivity for CD30, CD79a, and AE1/3 have been reported.…”