Aberrant expression of TTF1, p63, and cytokeratins in a diffuse large B‐cell lymphoma

Abstract

Pancytokeratins and TTF‐1 are used in working up carcinomas of unknown primary and p63 is expressed in many cell lineages. We present a case of a TTF‐1, p63, and cytokeratins positive small round blue cell lesion presenting in a patient with enlarged right supraclavicular lymph nodes and multiple solid pulmonary nodules. The preliminary report to the clinical team was “suspicious for carcinoma.” However, after a complete work up the final diagnosis of diffuse large B‐cell lymphoma, nongerminal center B‐cell phenotype, “double expressor,” was rendered (based on Han's algorithm). This case brings up significant diagnostic dilemma as some lymphoid malignancies can morphologically mimic poorly differentiated carcinoma and stain positive for carcinoma markers. Additionally, the frequently used TTF‐1 SPT23 antibody clone has strong nuclear staining in rare cases of DLBCL, which is a diagnostic pitfall. To our best knowledge this is the first reported case of DLBCL staining positive for three carcinoma markers.

Cytokeratin and CD56 aberrant co‐expression in diffuse large B‐cell lymphoma, NOS misinterpreted as metastatic neuroendocrine carcinoma by FNAC

“…As new antibodies for ICC and immunohistochemical reactions emerge on the market, certain markers may show positive when not expected. For instance, Chornenkyy and Xiaoqi recently reported a case of DLBCL in FNAC with cytokeratin, TTF‐1, and p63 co‐expression 3 . Therefore, excisional biopsy and histology should be performed in all cases where unusual morphological and/or immunophenotypical features observed in FNAC samples preclude accurate diagnosis.…”

“…Aberrant expression of different lineage markers is a rare but well‐described phenomenon in DLBCL, NOS. 2 , 3 Among others, aberrant expression of cytokeratins and CD56 in haematological neoplasms has also been reported in a few case studies. 4 , 5 Their expression may cause diagnostic problems, especially in fine needle aspiration cytology (FNAC), where indistinct cell morphology and limited antibody panels used for immunophenotypic studies preclude accurate diagnosis.…”

“…Aberrant expression of different lineage markers is a rare but well‐described phenomenon in DLBCL, NOS 2,3 . Among others, aberrant expression of cytokeratins and CD56 in haematological neoplasms has also been reported in a few case studies 4,5 .…”