Dermoscopy of primary cutaneous B- and T-cell lymphomas and pseudolymphomas presenting as solitary nodules and tumors: a case-control study with histopathologic correlation.

Background: Primary cutaneous lymphomas (PCLs) and pseudolymphomas presenting as single pink-red nodules/tumors are highly unspecific and include a wide differential diagnosis.

Objective: To describe the dermoscopic characteristics of PCL/pseudolymphoma.

Methods: In this retrospective, case-control study, we evaluated the dermoscopic features of patients with solitary PCL/pseudolymphoma tumors and compared them to a control group of non-lymphomatous, nonpigmented, solitary tumors (e.g., basal cell carcinoma, amelanotic melanoma, etc).

Results: We included 14 patients with PCL/pseudolymphomas and 35 controls. T-cell and B-cell lymphoma proportions were 28.6% (n = 4) and 71.4% (n = 10), respectively. Compared to controls, most lymphomas presented dermoscopically with orange color (71.4% vs. 14.2%, P < 0.001), follicular plugs (85% vs. 2.8%, P < 0.001), and as  organized lesions (85% vs. 31.4%, P = 0.001). Coexistence of orange color and follicular plugs had an odds ratio (OR) of 2.8 (P < 0.001), highly suggestive of PCL . The kappa index for independent observers was 0.66, 0.49, 0.43 for orange background, follicular plugs, and organized lesion, respectively. Histopathologic correlation was performed in six PCL cases and showed dense diffuse and perifollicular lymphocytic infiltrate in all cases and keratin plugs in five of six cases, possibly correlating with the orange color and the follicular plugs, respectively.

Conclusion: Primary cutaneous lymphomas/pseudolymphomas present with characteristic dermoscopic findings irrespective of immunohistochemical subtype.