Clonal T-Cell Receptor Gamma-Chain Gene Rearrangements In Differential Diagnosis Of Lymphomatoid Papulosis From Skin Metastasis Of Nodal Anaplastic Large-Cell Lymphoma (Vol 147, Pg 943, 2011)

Background: In patients with a history of nodal anaplastic large-cell lymphoma (ALCL), differentiation of type C lymphomatoid papulosis from cutaneous involvement of systemic ALCL may be challenging because the 2 entities may exhibit identical histologic features. Although metastatic ALCL generally carries the same clone as the primary lymphoma, expression of a distinct clone likely represents a distinct process.Observations: A 54-year-old white man had a history of anaplastic lymphoma kinase 1-negative ALCL in the right inguinal lymph node 6 years ago. A complete response was achieved after 6 cycles of CHOP (cyclophosphamide, doxorubicin, vincristine [Oncovin], and prednisone administered in 21-day cycles) and radiation therapy. After 31/2 years, the patient observed waxing and waning papules and nodules. Examination of the biopsy specimen revealed a dense CD30(+) lymphocytic infiltrate; no evidence of systemic malignancy was evident on positron emission tomography. Although clinically the presentation was consistent with lymphomatoid papulosis, metastatic ALCL had to be excluded. Polymerase chain reaction analysis with T-cell receptor gamma-chain gene rearrangement (TCR-gamma R) was performed on the original lymph node and new skin lesions. Results of the TCR-gamma R analysis were positive for clonality in both lesions. However, separate clonal processes were identified. The identification of distinct clones supported the clinical impression of lymphomatoid papulosis.Conclusion: Polymerase chain reaction analysis of TCR-gamma R is a useful method for distinguishing different clonal processes and is recommended when differentiation of primary and secondary lymphoproliferative disorders is required.