Background. CD30 (Ki‐1)‐positive anaplastic large cell lymphoma (LCL) has been described as a morphologically distinct group of LCL that generally are associated with a poor prognosis. Recent studies indicate that these lymphomas, when confined to the skin, have a favorable prognosis. However, there is no consensus regarding the definition of these primary cutaneous CD30‐positive LCL. Reported patients have been selected variously on the basis of morphologic (anaplastic cytology) or immunophenotypical (expression of CD30 antigen) criteria. Methods. At two recent workshops aimed to achieve consensus on the definition and terminology of these lymphomas, the clinical, histologic, and immunophenotypical data of 47 patients with primary cutaneous CD30‐positive LCL from five collaborating European centers were analyzed. Results. Characteristic clinical features were presentation with solitary or localized skin lesions (42 of 47 patients), frequent cutaneous relapses (15 patients), and partial or complete spontaneous remission of skin lesions (11 patients). Twelve of 47 (25%) patients developed extracutaneous disease. The favorable prognosis of these lymphomas is indicated by the follow‐up data that show that 36 of 47 patients are alive and in complete remission, only four disease‐related deaths have occurred, and the overall median survival is 42 months (range, 2–130 months). There were no differences in clinical presentation, course, or prognosis between anaplastic and nonanaplastic CD30‐positive LCL. Conclusion. The results of this study indicate that primary cutaneous CD30‐positive LCL, regardless of their morphologic classification (anaplastic or nonanaplastic) can be considered as a distinct type of cutaneous T‐cell lymphoma. Recognition of this type of cutaneous lymphoma is important because it may prevent patients from unnecessary aggressive treatment.

Our findings indicate that CD30+ cutaneous lymphoproliferative disorders comprise a spectrum of closely related skin lesions, which can be assigned a relatively favorable or unfavorable prognosis by a combined clinical and pathologic analysis.

This study shows that primary mediastinal B-cell lymphoma with sclerosis is a distinctive subtype of NHL with unique clinicopathologic aspects and aggressive behavior. Prompt recognition and aggressive treatment may provide long survival in a good proportion of cases. However, a subset of patients is extremely refractory to first- and second-line treatment. Conventional prognostic factors seem inadequate to identify these very-poor-risk cases.

Sinus histiocytosis with massive lymphadenopathy (SHML), or Rosai-Dorfman disease, is rare histiocytic disorder of known origin which shares several cell markers with Langerhans' cell histiocytosis (LCH). Although Rosai-Dorfman cells exhibit an aberrant immunophenotype, the indolent clinical course of SHML suggests a reactive disorder rather than a neoplastic process. Until recently this was prevailing opinion concerning LCH also, but recent studies have detected clonal histiocytes in all forms of this latter condition, which is therefore considered a clonal neoplastic disorder with highly variable biological behaviour. To determine whether the histiocytic proliferation in SHML is polyclonal or clonal we used X-linked polymorphic loci to assess clonality in lesional tissues in two women. Polymorphic regions of the human androgen receptor (HUMARA) locus were amplified by polymerase chain reaction (PCR) analysis. The HUMARA locus was informative in both cases and, following digestion with methylation-sensitive enzymes, typical polyclonal X-inactivation patterns were observed. Since abnormal cells accounted for > 90% lesional tissue cells, we conclude that Rosai-Dorfman histiocytic proliferation was polyclonal in the women studied.

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