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Cutaneous lymphoid hyperplasia and cutaneous marginal zone lymphoma: comparison of morphologic and immunophenotypic
M F Baldassano1, E M Bailey, J A Ferry
1Department of Pathology, Massachusetts General Hospital, Boston 02114, USA.
Insights
Cutaneous marginal zone lymphoma (MZL) and cutaneous lymphoid hyperplasia (CLH) present similarly but can be distinguished by specific histological features. Differentiating these conditions is crucial for accurate diagnosis and patient management.
Area of Science:
- Dermatopathology
- Hematopathology
- Oncology
Background:
- Cutaneous marginal zone lymphoma (MZL) is an indolent low-grade B-cell lymphoma.
- It shares clinical and histological similarities with benign cutaneous lymphoid hyperplasia (CLH).
- Distinguishing between MZL and CLH is challenging on routine tissue sections.
Purpose of the Study:
- To identify histological and immunophenotypic features that differentiate cutaneous MZL from CLH.
- To evaluate the diagnostic utility of routinely processed tissue specimens.
Main Methods:
- Comparative analysis of 16 CLH biopsy specimens and 16 cutaneous MZL cases (9 primary, 7 secondary).
- Histological examination of hematoxylin-eosin stained sections.
- Immunohistochemical staining for immunoglobulin light chains and B:T cell ratios on formalin-fixed paraffin-embedded tissues.
Main Results:
- Cutaneous MZL showed a diffuse proliferation of marginal zone cells, plasma cell zones, absence of epidermal changes, reactive germinal centers, and diffuse infiltration.
- Dutcher bodies were exclusive to MZL.
- Monotypic immunoglobulin light chain expression by plasma cells identified MZL in 70% of cases; a B:T cell ratio ≥ 3:1 supported MZL in 40% of cases.
Conclusions:
- While clinically similar, cutaneous MZL and CLH can be differentiated using specific histological features.
- Presence of reactive follicles, marginal zone cells, and plasma cell sheets favor MZL.
- Immunohistochemistry, particularly light chain restriction in plasma cells and B:T cell ratios, aids in definitive diagnosis.
Abstract:
Cutaneous marginal zone lymphoma (MZL) is a recently described low-grade B-cell lymphoma that usually follows an indolent course. This tumor shares many histologic and clinical features with cutaneous lymphoid hyperplasia (CLH), a benign reactive lymphoid proliferation. Sixteen biopsy specimens from 14 patients with CLH were studied, and compared with 16 cases of cutaneous MZL (9 primary cutaneous, 7 with secondary involvement of the skin) to determine whether there were features that would permit their distinction on routinely fixed, paraffin-embedded tissue sections. Both disorders showed a female preponderance (CLH: 9 F, 5 M; MZL: 11 F, 5 M). The median age was also similar (CLH: 54 years; cutaneous MZL: 55 years). CLH was most common on the arm (8) and the head and neck (7) but also involved the trunk (1); primary cutaneous MZL most often involved the limbs (3), trunk (3), and head and neck (3). Lymphoma did not develop in any of the 14 CLH patients (follow-up ranging from 9 to 246 months, mean 62 months). Six of 9 patients with primary cutaneous MZL and all 7 patients with secondary cutaneous MZL experienced relapses, most commonly isolated to skin or a subcutaneous site. On hematoxylin-eosin stained sections, a diffuse proliferation of marginal zone cells (p < 0.0001), zones of plasma cells (p = 0.01), the absence of epidermal change (p = 0.01), reactive germinal centers (p = 0.03), and a diffuse pattern of dermal or subcutaneous infiltration (p = 0.03) were more often seen in cutaneous MZL. A dense lymphocytic infiltrate, bottom-heavy or top-heavy growth pattern, eosinophils, and a grenz zone were seen equally often in both disorders. Dutcher bodies were observed only in cutaneous MZL. Immunoperoxidase stains on formalin-fixed paraffin-embedded tissue sections showed monotypic expression of immunoglobulin light chains by plasma cells in 11 of 16 MZL cases. By definition, no case with monotypic plasma cells was diagnosed as CLH. In CLH, T cells usually outnumbered B cells, and a B:T cell ratio > or = 3:1 was not observed in any case. By contrast, 40% of the MZL cases showed a B:T cell ratio > or = 3:1. No coexpression of CD20 and CD43 was seen in any case of either MZL or CLH. In summary, the clinical presentations of CLH and MZL are similar. In contrast to historical criteria for diagnosing cutaneous lymphoid infiltrates, the presence of reactive follicles favors a diagnosis of cutaneous B-cell lymphoma (CBCL). In addition, a bottom-heavy or top-heavy growth pattern is not a distinctive finding. Marginal zone cells and zones or sheets of plasma cells are strong morphologic indicators of marginal zone lymphoma. The diagnosis of CBCL can be supported in 40% of the cases by demonstrating a B:T cell ratio of > or = 3:1, and confirmed in 70% of the cases by demonstrating monotypic light chain expression of plasma cells on paraffin sections.
