Hist-O-08 - Macular type of primary cutaneous B-cell lymphoma: extension of the clinical and histopathological patterns

Abstract

<h3>Importance:</h3> Primary cutaneous B-cell lymphoma (PCBCL) classically presents with papules, plaques, nodules/ tumors. Previous reports of PCBCL manifesting with macular lesions are scarce, and focused on primary cutaneous follicle-center cell lymphoma (PCFCL), with limited data on its clinicopathological correlation. <h3>Objective:</h3> To report our experience with PCBCL presenting with erythematous macules. <h3>Design:</h3> Retrospective cohort. <h3>Setting:</h3> Two tertiary cutaneous-lymphoma outpatient clinics. <h3>Participants:</h3> Fourteen patients with low-grade PCBCL manifesting with erythematous patches, diagnosed and managed between January 2000 and December 2019. <h3>Intervention:</h3> Clinical data were collected from the medical files. Biopsy specimens of the macules, and if present of the typical nodular/tumoral lesions, were reviewed. <h3>Main outcome measures:</h3> Characterizing the macular lesions of low-grade PCBCL. <h3>Results:</h3> There were 14 patients, aged 16–67 years, 8 had PCFCL and 6 had primary cutaneous marginal zone lymphoma (PCMZL). All had erythematous macules, measuring 1–15 cm, which mimicked: figurate erythema, interstitial granuloma annulare, livedo reticularis, vascular tumors, and in 7 patients showed also follicular accentuation, thus simulated early-stage folliculotropic mycosis fungoides. In 3 patients macules were the presenting lesions, in 2 as the sole manifestation, whereas in 12 patients typical PCBCL lesions were observed during the disease course. On histopathology, the macular lesions showed in all superficial and deep perivascular infiltrates and in all but 1 also periadnexal lymphoid infiltrates. Microdules were observed in 11 biopsy specimens, in only 4 of them nodular infiltrates were also observed B-cells comprised the majority of the lymphocytes in only 4 patients, while in the remaining 10, B and T-cells were either equally distributed or T-cells outnumbered B. Polymerase-based analysis of a patch showed immunoglobulin heavy chain monoclonality in 7 of 11 cases tested. <h3>Conclusions and relevance:</h3> PCMZL and not only PCFCL, as previously reported, may manifest with erythematous macules, rarely as the sole presentation, and more often in conjunction with typical lesions. Histopathologically, the macules are characterized by distinct perivascular-periadnexal and micronodule pattern, and in most of the cases without the nodule formation classically observed in such lymphomas. Physicians should be aware of this unique variant representing a pitfall in the clinical and histopathologic diagnosis of low-grade PCBCL.