The diagnosis of mantle cell lymphoma (MCL) requires a multifaceted approach with integration of morphology and immunophenotype, supported by cyclin D1 positivity or identification of t(11;14)(q13;q32). Interphase fluorescence in situ hybridisation (FISH) using a dual colour, dual fusion probe strategy for t(11;14) is a rapid test with high sensitivity and specificity for MCL, and is easily performed on routine bone marrow aspirate or peripheral blood specimens. This test has become the method of choice for many pathologists to confirm a diagnosis of MCL. This report describes a case of MCL with a normal (negative) FISH signal pattern for t(11;14) that was found to be cyclin D1 positive by immunohistochemistry in tissue sections. This case illustrates the need for additional testing when the t(11;14) abnormality is not identified but the morphology and immunophenotype are otherwise suggestive of MCL.