Final Diagnosis -- Small lymphocytic lymphoma

Comment: The current specimen is diagnostic of a low-grade small lymphocytic lymphoma that appears to be arising within a Warthin's tumor.

DISCUSSION:

Although rare, the diagnosis of malignant lymphoma involving a Warthin's tumor has been reported in the literature. In this current case, the patient has both features of a typical Warthin's tumor as well as a low-grade non-Hodgkin lymphoma. Since this case was sent as a consultation, no flow cytometric immunophenotypic studies were available. In addition, no bone marrow or peripheral blood was available for analysis. The immunohistochemical-staining pattern was consistent with small lymphocytic lymphoma (CD20 positive, CD5 positive, and CD43 positive, and cyclinD1 negative. The absence of detectable CD23 staining by immunohistochemistry is common. Small lymphocytic lymphoma is characteristically CD23 positive using flow cytometric analysis.

Chronic lymphocytic leukemia/small lymphocytic lymphoma (SLL/CLL) is a mature B-cell neoplasm of monomorphic small, round lymphocytes in the peripheral blood, bone marrow and lymph nodes, admixed with prolymphocytes and para-immunoblasts. A diagnosis of SLL (but not CLL) can be made histologically in the absence of bone marrow or blood involvement. The architecture of an involved area (lymph node or other tissue) consists of effacement of the nodal architecture with a pseudofollicular pattern of regularly distributed pale areas containing larger cells in a dark background of small cells. The small lymphocytes predominate and usually show a round nucleus and occasionally small nucleolus.

The differential diagnosis of small B-cell lymphoid neoplasms (small round lymphocytes) include: B-cell chronic lymphocytic leukemia/small lymphocytic lymphoma, follicular lymphoma, mantle cell lymphoma and marginal zone lymphoma. Follicular lymphoma was ruled out based on morphology and the fact that the majority of follicular lymphomas are CD10 positive, bcl6 positive and CD43 negative. Based on the immunohistochemical staining panel mantle cell lymphoma was ruled out due to the negative cyclinD1. A marginal zone lymphoma was not considered in the diagnosis due to morphology and immunohistochemical staining pattern.

REFERENCES:

1. Jaffe ES, Harris NL, Stein H Vardim JW (Eds): WHO Classification of Tumours. Pathology and Genetics of Tumours of Haematopoietic and Lymphoid Tissues. IARC Press: Lyon 2001.
2. Barnes, EL (ed): Surgical Pathology of the Head and Neck. Dekker, Marcel Inc.: 2nd ed New York 2001.
3. Chen CC et al Classification of small B-cell lymphoid neoplasms using a paraffin section immunohistochemical panel. Appl Immunohistochem 8(1): 1-11, Mar 2000.
4. Medeiros, LJ, et al. Malignant Lymphoma Involving A Warthin's Tumor: A Case with Immunophenotypic And Gene Rearrangement Analysis. Hum Pathol 21:974-977; 1990.
5. Bunker, ML and Locker, J. Warthin's Tumor with Malignant Lymphoma: DNA Analysis of Paraffin-Embedded Tissue. Am J Clin Pathol 91:341-344; 1989.

Contributed by Maurice R. Grant, MD and Fiona Craig, MD.