Contribution of longitudinal follow up and clinical pathological correlation in the diagnosis CD30-positive skin infiltrates.

The diagnosis of a CD30+ cutaneous infiltrate is often difficult and requires clinicopathologic correlation. To further evaluate this challenge, initial clinical and histopathologic diagnoses were correlated with final clinicopathologic diagnosis in 44 cases with CD30 immunopositivity. Dermatopathologic evaluation confirmed the initial clinical diagnosis in 65% of the suspected benign cases, all cases of suspected lymphomatoid papulosis (LyP), and 72% of clinically malignant cases. In the 25 patients with clinical suspicion for lymphoma, the histopathologic diagnoses included lymphoma in 18, LyP in 2, CD30+ lymphoproliferative disorder (CD30 LPD) in 3 and hypersensitivity reaction in 2 patients. Clinicopathologic correlation led to a change in three cases diagnosed histopathologically as anaplastic large cell lymphoma (ALCL) reclassified as LyP type C, and one patient diagnosed as CD30 LPD clinically evolved as herpes virus infection. Furthermore, five cases reported as CD30 LPD received more specific diagnoses after clinicopathologic correlation (LyP type C in three, and ALCL in two patients). Clinicopathologic correlation is essential in establishing the correct diagnosis of CD30 LPD, in particular the distinction of ALCL from LyP type C. In this setting, the histopathologic diagnosis of CD30 LPD is advisable in the absence of clinical data.