Signet-ring cell lymphoma: clinicopathologic, immunohistochemical, and fluorescence in situ hybridization studies of 7 cases.

CONTEXT: Signet-ring cell lymphoma (SRCL) is a rare morphologic variant of non-Hodgkin lymphoma. Although it was initially reported as a rare morphologic variant of follicular lymphoma (FL), SRCL has to date been described in most types of non-Hodgkin lymphoma, mostly as single-case reports.

OBJECTIVE: To study SRCL systematically by immunohistochemical stains and fluorescent in situ hybridization analyses.

DESIGN: Seven SRCL cases were stained for CD3, CD5, CD20, PAX-5, CD10, CD21, CD23, cyclin D1, BCL2, BCL6, Ki-67, and MUM-1, and were analyzed by fluorescent in situ hybridization for BCL2, BCL6, MYC, and MALT1 rearrangements. Clinical information and patient outcome were reviewed in all patients.

RESULTS: The patients were 3 women and 3 men, ranging in age from 31 to 75 years (average 60.3 years). The lesions involved lymph nodes, tonsil, parotid gland, soft tissue, and breast. There were 4 FLs, 1 diffuse large B-cell lymphoma (DLBCL), 1 DLBCL with FL, and 1 DLBCL with marginal zone lymphoma. All cases had typical signet-ring cell morphology. They were positive for CD20 and BCL-2, and had low-to-intermediate Ki-67 proliferation index (10%-40%) except in the parotid DLBCL with FL (70%). BCL-6 was detected in all but 1 FL (6/7). Fluorescent in situ hybridization detected IGH/BCL2 translocation in 1 FL, increased BCL6 copy number in another FL, BCL6 rearrangement, and increased copy number of MYC and MALT1 in the DLBCL with marginal zone lymphoma.

CONCLUSIONS: The FL with signet-ring cell morphology (1/5) tends to lack IGH/BCL2 translocation, and an extended immunohistochemical study is recommended for correct diagnosis and classification of SRCL.