A Case of Generalized Crystal Storage Histiocytosis Presenting as Soft Tissue Sarcoma: Diagnostic Dilemma

Crystal storage histiocytosis (CSH) is a rare clinical entity. It comprises of benign histiocytes showing accumulation of refractile generally immunoglobulin crystals in the cytoplasm. Accumulation of non-immunoglobulin substances is also described, common being clofazimine, charcot-leyden, and cystine. Here, we present a case of generalized CSH presenting as a chest wall mass in a 62-year-old gentleman. X-ray showed a chest wall mass with destruction of the right sixth rib. Histopathological examination revealed plasmacytoma with the presence of histiocytes showing abundant pink cytoplasm. Bone marrow examination revealed the presence of plasma cells with dense azurophilic granules. The patient was started on chemotherapy for multiple myeloma. It is clinically important to identify these cases as part of published literature since it annotates poor prognosis to the generalised form of CSH compared to localized one. The unusual location, presence of morphologically distinct plasma cells in marrow, made the diagnosis challenging. The case also highlights the role played by immunohistochemistry to arrive at the right diagnosis.