Progressive nodular histiocytosis with normal karyotypic analysis.

Non-Langerhans cell histiocytoses (NLH) comprise a spectrum of diseases that includes sinus histiocytosis with massive lymphadenopathy, hemophagocytic lymphohistiocytosis, xanthogranuloma, and reticulohistiocytoma. Progressive nodular histiocytosis (PNH) is a rare NLH that microscopically mimics juvenile xanthogranuloma but presents with disseminated persistent and progressive papulonodules in adults. Herein, we describe a case of PNH presenting as diffuse, progressively enlarging papules, nodules, and pedunculated tumors in a 38-year-old male. The diagnosis is supported microscopically by the morphologic and immunohistochemical findings. Whereas conventional cytogenetic analysis of Langerhans cell histiocytosis and juvenile xanthogranuloma has previously been described, there are no reports of the karyotype of PNH. In our patient, conventional cytogenetic analysis of the tumor revealed a normal karyotype. Although these results may represent the overgrowth of normal stromal cells rather than lesional cells, we believe this to be an important finding, indicating karyotypic analysis will not allow for distinction between PCH and other NLH or Langerhans cell histiocytoses.