Human herpesvirus-8 genes are expressed in pulmonary inflammatory myofibroblastic tumor (inflammatory pseudotumor)

Inflammatory myofibroblastic tumors (inflammatory pseudotumors) of the gastrointestinal tract: how closely are they related to inflammatory fibroid polyps?

Inflammatory myofibroblastic tumors (inflammatory pseudotumors) and inflammatory fibroid polyps of the gastrointestinal tract both feature prominent inflammatory infiltrates admixed with spindle-shaped fibroblasts/myofibroblasts set in a collagenous, fibrovascular, or myxoid stroma. Erroneously, some have considered inflammatory fibroid polyps to be intraluminal manifestations of inflammatory myofibroblastic tumors. In this study, we have characterized the histopathology of inflammatory myofibroblastic tumors, tumors that have only rarely been reported in the gastrointestinal tract, and have focused on whether inflammatory myofibroblastic tumors and inflammatory fibroid polyps in the gastrointestinal tract are distinct or similar. Clinical, histopathologic, and immunohistochemical features of 38 inflammatory myofibroblastic tumors limited to the wall of the gastrointestinal tract were compared with those of 45 inflammatory fibroid polyps. Compared to patients with inflammatory fibroid polyps, those with inflammatory myofibroblastic tumors were younger (mean age 41 years vs. 53 years); had larger tumors (mean 8 +/- 5.2 cm vs. 3.6 +/- 4.6 cm); presented with abdominal pain, fever, and weight loss more frequently and less frequently had bowel obstruction. Inflammatory fibroid polyps had more eosinophils and fibrosis and fewer lymphoid cell infiltrates than inflammatory myofibroblastic tumors. A regular vascular pattern was a feature of inflammatory fibroid polyps but not of inflammatory myofibroblastic tumors. Most (82%) inflammatory fibroid polyps were positive for CD34 versus none of the inflammatory myofibroblastic tumors. Smooth muscle actin was more frequently positive in inflammatory myofibroblastic tumors than in inflammatory fibroid polyps (86% versus 13%). Inflammatory myofibroblastic tumors were much less frequent and were more evenly distributed in the gastrointestinal tract than inflammatory fibroid polyps. Both appear to be benign processes. Inflammatory myofibroblastic tumors, but not inflammatory fibroid polyps, had a tendency to recur. In conclusion, inflammatory myofibroblastic tumors of the gastrointestinal tract are extremely rare and differ clinically, histologically, and immunohistochemically from inflammatory fibroid polyps.

Inflammatory pseudotumor of lymph node and spleen: an entity biologically distinct from inflammatory myofibroblastic tumor

Inflammatory pseudotumors (IPTs) of the lymph node and spleen are an uncommon, benign cause of lymphadenopathy and/or splenomegaly that often bear striking clinicopathologic similarities to the inflammatory myofibroblastic tumors (IMTs) found in soft tissues. These tumors have classically been grouped together under the umbrella category of "inflammatory pseudotumor." Recent evidence shows that IMTs are in fact neoplastic processes that often harbor balanced chromosomal translocations involving the ALK kinase gene. These translocations result in expression of ALK kinase in IMTs as assessed by immunohistochemical studies. However, the relationship between IMT and IPT of the lymph node and spleen is uncertain. To determine if ALK tyrosine kinase expression is also present in IPT, 13 cases of IPT (9 involving lymph nodes, 4 splenic lesions) were examined for the presence of ALK tyrosine kinase by immunohistochemical staining on paraffin-embedded tissue. In addition, in situ hybridization studies for Epstein-Barr virus--encoded RNAs (EBER) and immunoperoxidase studies for human herpesvirus-8 (HHV8)--specific proteins were performed. All cases had clinical, morphologic, and immunophenotypic findings typical of IPT and had varying proportions of fibroblastic and inflammatory components. Age ranged from 11 to 75 (median, 40) years; 8 subjects were male, and 5 were female. None of the cases (0 of 13) had positive staining for ALK kinase or HHV8, and in 1 a lymph node (1 of 13) was focally positive for EBV (EBER) by in situ hybridization. The absence of ALK kinase as detected by immunohistochemical studies in IPT of the lymph node and spleen suggests that this entity is biologically distinct from the histologically similar IMT.

Anaplastic lymphoma kinase (ALK) expression in the inflammatory myofibroblastic tumor: a comparative immunohistochemical study

Inflammatory myofibroblastic tumor (IMT) is an uncommon mesenchymal neoplasm with a variable histologic appearance that may mimic other spindle cell processes, particularly nodular fasciitis, desmoid tumor, and in intra-abdominal locations, gastrointestinal stromal tumor. Recently, gene fusions involving ALK at chromosome 2p23 have been described in IMTs. The resultant ALK protein overexpression in the myofibroblastic component of these tumors is detectable by immunohistochemistry. We examined 73 IMTs, 20 cases of nodular fasciitis, 15 desmoid fibromatoses, and 15 gastrointestinal stromal tumors by immunohistochemistry using ALK-11, a rabbit polyclonal antibody that recognizes the C-terminus of the protein. ALK positivity was detected in 44 of 73 (60%) IMTs. All cases of nodular fasciitis, desmoid fibromatosis, and gastrointestinal stromal tumors were ALK negative (p < 0.001). These findings demonstrate that ALK positivity is common in IMTs, and immunohistochemistry using anti-ALK antibodies can be helpful in the differential diagnosis of these neoplasms. In addition, anti-ALK staining seems to correlate with those IMTs that have the typical tri-patterned histologic appearance and clinical presentation, providing additional support to the premise that IMT is a distinctive clinicopathologic entity within the broad category of inflammatory pseudotumors.

The emerging role of the human herpesvirus 8 (HHV8) in human neoplasia

The human herpesvirus 8 (HHV8) was initially described and characterised in Kaposi's sarcoma tissue. The virus was found in the lesion of most cases of Kaposi's sarcoma. Whilst there is a large body of evidence to implicate its role in the pathogenesis of Kaposi's sarcoma, it has recently been found that the virus may also be important in a number of other human neoplasias. This review will examine the molecular pathology of HHV8 in the pathogenesis of Kaposi's sarcoma and summarise the current evidence and postulated mechanisms in its role in other human neoplasias.