Lymphoproliferative Neoplasms 9.7.1
Definition, Epidemiology, Pattern of Growth
Lymphoproliferative neoplasms include a variety of different lesions originating from lymphoid cells. The main lymphoproliferative neoplasms are Hodgkin and non-Hodgkin lymphomas, which originate from lymphocytes; they differ for etiopathogenetic factors, pattern of growth, and prognosis.
Lymphomas account for 3% to 5% of all malignancies, and up to 60% of cases are non-Hodgkin lymphomas (Quraishi et al. 2000). Hodgkin lymphoma develops within lymph nodes and may then spread, in a quite predictable fashion, through lymphatic channels to contiguous lymph node chains and then to other structures. Non-Hodgkin's lymphomas, which are classified into B and T-NK subtypes according to lymphocytic phenotype, may originate from lymph nodes or, in a quite consistent percentage of cases (20-40%), from an extranodal site (Fajardo-Dolci et al. 1999). Non-Hodgkin lymphomas may be characterized by a dissemination of the disease, with involvement also of nodal and extranodal sites far from the original site.
In the head and neck, about 60% of lymphomas have an extranodal origin (Quraishi et al. 2000). Sinonasal tract may be involved by primary lesions (nasal cavity T-NK lymphoma and marginal zone B-cell lymphoma) and secondary lesions. For primary neoplasms, it is possible an exclusive localization within the sinonasal tract; conversely, all secondary lesions should be considered as a systemic disease. Sinonasal lesions, either primary or secondary, are mostly non-Hodgkin lymphomas, while Hodgkin lymphoma is very rarely encountered.
A difference in terms of neoplastic cells subtype, epidemiology, and site of origin between Western World and Far East is well known. In the Western World, non-Hodgkin lymphomas are mainly B-cell subtype and sinonasal tract involvement varies between 0.2 and 2% of all non-Hodgkin lymphomas (Quraishi et al. 2000). In Far East and South America instead, the most frequent cell subtype is T or NK (Nakamura et al. 1997). In the Western World, non-Hodgkin lymphomas tend to affect paranasal sinuses in the elderly, whereas in Far East and South America the nasal cavity in younger people is mainly involved (Quraishi et al. 2000).
In relation to the etiopathogenesis, viruses such as Epstein-Barr and HTLV-1 are considered important agents, especially for specific lymphomas (i.e., Burkitt lymphoma and nasal NK-T lymphoma).
At presentation, non-Hodgkin lymphomas of the sinonasal tract are often bulky, with possible involve ment of the surrounding structures. They may display a tendency to destroy bony walls of the sinonasal tract, just like other aggressive malignancies; however, it is noteworthy that the lesion may also infiltrate and expand the bone (Nakamura et al. 1997) with a per-meative rather than a destructive pattern.
Involvement of regional lymph nodes is commonly observed; their distribution varies in relation of the location of the primary lesion within the sinonasal tract. Involvement of the skin, Waldeyer's ring, and extranodal organs has also been described, especially in the advanced stages of the disease.
Plasmacytoma, a lesion included among plasma-cell derived tumors, is more frequently observed in the sinonasal tract in the extramedullary form, while its solitary form is extremely rare. Extramedullary plasmacytoma develops in the head and neck area in up to 90% of cases, with an elective localization in the submucosa of the upper aerodigestive tract (Susnerwala et al. 1997; Majumdar et al. 2002). Most patients are elderly, and half of them have the lesion located within the sinonasal tract. According to Susnerwala et al. (1997), diagnostic criteria for extramedullary plasmacytoma are considered: 1) a biopsy proven plasma cell tumor involving a single extramedullary site with or without lymph node involvement; 2) a bone marrow biopsy showing less than 5% plasma cells, 3) normal skeletal survey. Extramedullary plasmacytoma cells may show a wide range of cell differentiation which goes from mature cells clones (Grade 1) to intermediate (Grade 2) and completely immature (Grade 3) ones (Kapadia et al. 1982).
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