Subcutaneous Pattern: Subcutaneous Lymphoproliferative Disorders

Abstract

Both inflammatory and malignant lymphoproliferative disorders can present as a predominantly subcutaneous infiltrative pattern. The prototype of subcutaneous inflammatory disorders is manifest by lupus profundus (panniculitis).

The panniculitis pattern is also characteristic of erythema nodosum, a painful eruption on the lower extremities, usually of young women, in reaction to bacterial infections, including tuberculosis, and drugs. An indeterminate lobular panniculitis pattern reflects uncertain etiology of a clinically benign disorder with a subcutaneous panniculitic pattern. Malignant disorders are subcutaneous panniculitis-like T-cell lymphoma (SPTCL), alpha-beta type, and the subcutaneous component of primary cutaneous gamma-delta T-cell lymphomas (PCGD-TCL); the latter also involve the dermis and epidermis. Immunohistochemistry combined with histology provides important data to distinguish the poor prognosis of PCGD-TCL with median survival of 15 months from the more favorable prognostic group of SPTCL of alpha-beta phenotype with 5-year median survival. Some patients with SPTCL have a history and pathology of lupus, suggesting a spectrum from lupus to SPTCL, similar to other cutaneous lymphoproliferative disorders discussed in this book. Recent molecular studies of SPTCL revealed upregulation of IFNγ-inducible indoleamine 2,3-dioxygenase (IDO-1) known for tumor-induced tolerance and which therefore is suspected to play a role in the tumorigenesis of SPTCL. This may explain the effectiveness of immunosuppressive agents in the treatment of SPTCL.