Cutaneous Crystal‐Storing Histiocytosis With Marginal Zone Lymphoma. A Case Report With A Striking Clinical Presentation

Cutaneous crystal-storing histiocytosis (CSH) is an extremely rare histopathologic finding of histiocytes accumulating crystals of immunoglobulin or paraproteins, often associated with lymphoplasmacytic malignancies. It commonly presents in a wide age range of both female and male adults with a history of a lymphoproliferative disorder. Dermatologic examination typically shows cutaneous nodules, plaques, or papules, which frequently present on the trunk, proximal extremities, head, and neck. Histopathologic examination demonstrates numerous large eosinophilic CD68-positive histiocytes with a wavy-granular appearance. Ultrastructural examination of the histiocytes shows refractile needle-like or rhomboid crystals in the cytoplasm. The crystals are composed of immunoglobulins, and typically, there is an associated monotypic B-cell population, often lymphoplasmacytic lymphoma or multiple myeloma. Herein, we describe a case with a striking clinical presentation of cutaneous CSH involving the entirety of the face, neck, chest, shoulders, and upper arms of a 63-year-old female with a history of marginal zone lymphoma (MZL).