Incidental small lymphocytic lymphoma/chronic lymphocytic leukemia in pelvic lymph nodes excised at radical prostatectomy.

CONTEXT: Incidental non-Hodgkin lymphoma is often unrecognized at the time of radical prostatectomy in patients with prostate cancer because of nonspecific symptoms and an inconspicuous pathology. The early identification of lymphoma allows optimal long-term management and prevention of significant morbidity.

OBJECTIVE: To show the subtlety of pathologic findings in cases of non-Hodgkin lymphoma in pelvic lymph nodes and the need for scrupulous attention to detail for diagnostic accuracy.

DESIGN: Histologic and immunohistochemical profiles of 18 consecutive cases of small lymphocytic lymphoma (SLL) incidentally identified in pelvic lymph node dissections were reviewed and compared with 22 cases of benign pelvic lymph node dissections.

RESULTS: Malignant nodes were grossly enlarged and averaged 3.2 cm in their greatest dimension. Histologically, 16 of the SLL cases were characterized by diffuse architectural effacement with obliterated sinuses and rare cortical follicles. Twelve of these cases showed evidence of pseudofollicles. Two cases showed an interfollicular growth pattern with occasional small pseudofollicles. In contrast, benign pelvic lymph nodes averaged 1.7 cm in their greatest dimension. Although most were architecturally distorted by fibrosis, all benign nodes were notable for patent sinuses. Immunohistochemistry was diagnostically helpful in several cases with equivocal morphology. All malignant cases had a B-cell phenotype with aberrant coexpression of T-cell-related antigens typical of SLL.

CONCLUSION: Incidental low-grade non-Hodgkin lymphoma identified at radical prostatectomy is often overlooked by both the urologist and the pathologist. Although malignant pelvic lymph node dissections frequently lack overt manifestations of lymphoma, attention to subtle morphologic features coupled with lymph node size and immunohistochemical findings should permit diagnostic accuracy.