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9 - Grade/differentiation unknown, not stated, or not applicable
Histiocytic medullary reticulosis [OBS]
Malignant histiocytosis [see code 9751/3]
True histiocytic lymphoma
True histiocytic sarcoma
A malignant proliferation of cells showing morphologic and immunophenotypic features similar to those of mature tissue histiocytes. There is expression of one or more histiocytic markers without accessory/dendritic cell markers. Neoplastic proliferations associated with Acute monocytic leukemia are excluded.
Tumor mass of macrophage/mature tissue histiocytic cells occuring in any of several sites. Most common sites: lymph nodes (one third), skin (one third), intestinal tract and other extranodal sites.
Histiocytic sarcoma typically presents in extranodal sites, most commonly intestinal tract, skin, and soft tissues. Others present with lymphadenopathy. Rarely, patients have a systemic presentation with multiple sites of involvement, sometimes referred to as "malignant histiocytosis" which was coded separately before 2010 as 9750/3. Patients may present with a solitary mass but systemic symptoms are relatively common, e.g. fever and weight loss. Skin manifestations may range from a benign-appearing rash to solitary lesions to numerous tumors on the trunk and extremities. Patients with intestinal lesions often present with intestinal obstruction. Hepatosplenomegaly and associated pancytopenia may occur. The bones may show lytic lesions. Histiocytic sarcoma is usually an aggressive neoplasm with a poor response to therapy although some exceptions have been reported. Most patients die of progressive disease reflecting the high clinical stage at presentation (stage III-IV) in the majority of patients.
Definitive Diagnostic Methods
Exclusion of B and T cell markers
Clonal IgH negative
TCR rearrangements are lacking
Absence of markers from non-histiocytic cells
Stem cell transplant
Corresponding ICD-9 Codes
202.3 Malignant histiocytosis
Corresponding ICD-10 Codes
C96.3 True histiocytic lymphoma
C96.1 Malignant histiocytosis
Corresponding ICD-10-CM Codes
(effective October 1, 2015 U.S. only)