Histiocytoma Explained

A histiocytoma is a tumour consisting of histiocytes. Histiocytes are cells that are a part of the mononuclear phagocytic system, a part of the body's immune system that consists of phagocytic cells, which are responsible for engulfing solid particles by the cell membrane to form an internal phagosome by phagocytes and protists. Myxofibrosarcoma had been classified as a type of histiocytoma. However, the World Health Organization (2020) reclassified myxofibrosarcoma as a malignant tumor in the category of fibroblastic/myofibroblastic tumors.^[1]

Types include:

• benign fibrous histiocytoma: This tumor has also been termed benign fibrous histiocytomas of the skin, superficial/cutaneous benign fibrous histiocytomas, common fibrous histiocytoma, and more recently dermatofibroma. The use of "histiocytoma" in these terms refers more to the morphologic appearance of some of the cells that comprise these lesions rather than their lineage: studies to date have not fully determined the lineage of the neoplastic cells in dermatofibroma tumors^[2] but recent cell marker studies suggest these cells originate from fibroblasts rather than histiocytes.^[3]
• malignant fibrous histiocytoma: This tumor is now termed undifferentiated pleomorphic sarcoma (UPS) because more recently developed immunohistochemistry and cytogenetic analyses suggest that its neoplastic cells most likely arise from mesenchymal stem cells^[4] or fibroblasts^[5] rather than histiocytes.
• histiocytoma (dog)

Notes and References

1. Sbaraglia M, Bellan E, Dei Tos AP . The 2020 WHO Classification of Soft Tissue Tumours: news and perspectives . Pathologica . 113 . 2 . 70–84 . April 2021 . 33179614 . 8167394 . 10.32074/1591-951X-213 .
2. Book: Myers . David J. . Fillman . Eric P. . StatPearls . 2021 . StatPearls Publishing . https://www.ncbi.nlm.nih.gov/books/NBK470538/ . Dermatofibroma . 29262213 .
3. Kirschnick LB, Schuch LF, Silveira FM, Só BB, Martins MA, Lopes MA, Vargas PA, Santos-Silva AR, Carrard VC, Vasconcelos AC, Wagner VP, Martins MD . Benign fibrous histiocytoma of the oral and maxillofacial region: A systematic review . Oral Surgery, Oral Medicine, Oral Pathology and Oral Radiology . 133. 2. e43–e56. July 2021 . 34511357 . 10.1016/j.oooo.2021.07.003 . 237495526 .
4. Book: Robles-Tenorio . Arturo . Solis-Ledesma . Guillermo . StatPearls . 2021 . StatPearls Publishing . https://www.ncbi.nlm.nih.gov/books/NBK570612/ . Undifferentiated Pleomorphic Sarcoma . 34033374 .
5. Wu Y, Liu X, Lv Y, Li Z . Malignant fibrous histiocytoma of the floor of mouth: a case report and review of the literature . Journal of Stomatology, Oral and Maxillofacial Surgery . 123. 3. e106–e111. July 2021 . 34224923 . 10.1016/j.jormas.2021.06.017 . 235745120 .