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Atypical “hairy cell-like” presentation of leukemic mantle cell lymphoma

Mantle cell lymphoma (MCL) is a mature B-cell neoplasm that accounts for 3%–10% of malignant lymphomas [1]. Peripheral blood (PB) involvement occurs in one fifth to one quarter of the cases [2]. MCL is cytologically characterized by small to medium-sized lymphoma cells with irregular nuclear contours that may show clefts [1–3]. However, in contrast to other types of mature B-cell lymphoma, the cells in MCL tend to be more pleomorphic, which is reflected by the definition of four cytologic variants by the World Health Organization (WHO). The recently published WHO classification of tumors of hematopoietic and lymphoid tissues differentiates between a small cell, a marginal-zone like, a blastoid and a pleomorphic variant [1]. To the best of our knowledge, a MCL variant showing cytoplasmatic projections resembling those observed in hairy cell leukemia (HCL), hairy cell leukemia variant (HCL-V) or splenic lymphoma with villous lymphocytes (SLVL), has been rarely reported in the literature so far. In one case report, an intermediate or hybrid lymphoma, demonstrating features of both MCL and monocytoid B-cell lymphoma, simulating HCL, was described [4]. The authors of a previous study reviewed cases of malignant lymphoma presenting with isolated splenomegaly and observed a few cases of MCL in which the cells sometimes showed short, fine cytoplasmatic villi [5]. In this case report we describe an atypical “hairy cell-like” morphological presentation of MCL. An 80-year-old Caucasian man presented with intermittent fever, chills and night sweat. Computed tomography revealed abdominal and retroperitoneal lymphadenopathy as well as a marked splenomegaly with a diameter of 20 cm. A complete blood cell count performed by an ADVIA 2120i hematology analyser (Siemens, Vienna, Austria) showed moderate anemia with a hemoglobin concentration of 9.1 g/dL (14–18) (SI: 5.65 mmol/L), moderate thrombocytopenia of 77 × 103/μL (140–400) and a white blood cell count of 11.16 × 103/μL (4–9) with 13% neutrophils, 78% lymphocytes, 8% monocytes and 1% eosinophils. Examination of a PB smear stained according to the May-Grünwald-Giemsa technique confirmed the lymphocytosis of 78%. The lymphocytes were atypical small to intermediate-sized cells with mainly oval and sometimes irregular and indented nuclei with often singular nucleoli and moderately condensed chromatin. The cytoplasm was moderate in amount and weakly to moderate basophilic, with irregular margins and hairy-like projections in about 70% of the lymphocytes (Figure 1A). The projections were mostly distributed over the whole circumference of the cells or sometimes appeared as bipolar. These cytoplasmatic changes were restricted to the atypical lymphocytes, whereas the granular and typical lymphocytes did not show any villous projections. Based on the observed morphological features, leukemic B-cell malignant lymphoma such as SLVL, HCL or HCL-V was suspected and further investigations were performed. By flow-cytometric immunophenotyping of a PB specimen, the leukemic cells were positive for CD19, CD20, lambda light chain and CD5, weakly positive for CD23 and CD43, and negative for CD10. Bone marrow (BM) cytology revealed an infiltration by atypical lymphocytes showing the same morphological features as in the PB film (Figure 1B). About 30% of the BM aspirate cellularity consisted of lymphoma cells. The histopathological examinations confirmed the presence of lymphomatous BM infiltration. The pattern of BM *Corresponding author: Christoph Robier, MD, PD, Institute of Laboratory Diagnostics, Hospital of the Brothers of St. John of God, Graz, Bergstr. 27, 8020 Graz, Austria; and Clinical Institute of Medical and Chemical Laboratory Diagnostics, Medical University of Graz, Graz, Austria, Phone: +43 316 5989 26671, Fax: +43 316 5989 21505, E-mail: christoph.robier@bbgraz.at Gerald Hoefler: Diagnostic and Research Institute of Pathology, Medical University of Graz, Graz, Austria Margot Egger: Department of Laboratory Medicine, Konventhospital Barmherzige Brueder Linz, Linz, Austria Eva Hubmann: Department of Internal Medicine 1, Hospital of the Brothers of St. John of God, Graz, Austria