[Lymphomatoid papulosis: a clinicopathologic analysis and whole exome sequencing]

Objective: To study the clinicopathologic characteristics and immunophenotype of lymphomatoid papulosis(LyP), followed by exon mutation analysis with focus on gene mutations involved in apoptosis pathway and other possible pathogenic genes. Methods: Clinical data analysis and immunohistochemical staining were carried out in 20 cases of LyP. Whole exome sequencing technology was employed in 2 cases of type C of LyP. Results: Of the 20 cases, there were 9 males and 11 females with a median age of 28.6 years. Nineteen patients presented with multiple papules and nodules, and one case presented with only one tumor nodule. Of the fifteen cases with available followed-up data, all were alive (20-155 months). Histologically, the tumors primarily involved the dermis and subcutaneous layer, in which 6 were type A, 3 were type B, 10 were type C and 1 was type D. Main infiltration patterns included wedge-shaped, band-like, sheets and large nodular. Immunohistochemistry showed that most cases expressed CD30 in the large tumor cells. Sixteen cases expressed CD3, 17 cases expressed CD4 and 8 cases expressed CD8. Sixteen cases expressed TIA1. Ten cases expressed GrB and 1 case expressed CD15. All but one case did not expressed CD20. All cases did not express ALK1.A total of 101 common non-synonymous mutations were detected in 2 cases of LyP type C by whole exome sequencing, including 87 missense mutations, 6 missense mutation/frame-shift deletions, 2 missense mutation/nonframe-shift deletions, 5 frame-shift deletions, 1 missense mutations/synonymous mutation. Syndecan-1(SDC1), COL4A1, Laminin-5 were involved in the extracellular matrix receptor pathway. Conclusions: Clinical presentations are crucial for the diagnosis of LyP. LyP has a favorable prognosis. SDC1, COL4A1 and Laminin-5 gene mutations may be associated with tumor recurrence or progression into a higher gradelymphoma.