Clonal heterogeneity and its association with skin lesions in canine epitheliotropic cutaneous T-cell lymphoma

The types of skin lesions in canine epitheliotropic cutaneous T-cell lymphoma (ECTCL) vary markedly; however, the mechanisms underlying this diversity remain unclear. Human ECTCL exhibits clonal heterogeneity, with different clones of neoplastic lymphocytes being observed in skin lesions from the same patients. Therefore, we hypothesised that diversity in skin lesions may be attributed to clonal heterogeneity.

To evaluate clonality and its association with skin lesions.

PCR for T-cell receptors was performed on 25 formalin-fixed paraffin-embedded lesional skin samples derived from eight ECTCL cases. A fragment analysis was performed to establish whether clonal patterns were identical or nonidentical between lesions. The associations of clonal patterns with the types and histopathological features of skin lesions were investigated by statistical analyses. A transcription analysis was also conducted to examine the expression of recombination-activating gene (RAG)1 in skin lesions.

The fragment analysis identified only one case with an identical clonal pattern in all skin lesions. Nonidentical clonal patterns were detected in the seven other cases. Clonal patterns were not associated with the types of skin lesions or histopathological features. The transcription analysis did not detect RAG1 in any skin lesions.

The present study is the first to report clonal heterogeneity in canine ECTCL that was not associated with the clinical or histopathological features of skin lesions. The results obtained also suggested that clonal heterogeneity originated not in the skin.