Anti-Histone H3.3 G34W antibody is a sensitive and highly specific immunohistochemistry marker for the diagnosis of Giant cell tumor of bone. A validation based on analysis of 198 cases from a single centre in India

Context: The diagnosis of giant cell tumor of bone (GCTB) is difficult in small biopsies with unusual age of presentation, location, and extensive secondary changes. Most of the GCTBs harbor H3F3A G34W mutations with a subset of cases showing alternate G34V, G34R, and G34L mutations. Objectives: To analyze the expression of anti-histone H3.3G34W antibody in different cellular components of GCTB across different locations and presentations (including the unusual ones) and validate the utility of this antibody in the diagnosis of GCTB and differentiate it from the other osteoclast-like giant-cell-rich lesions. Design: Immunohistochemistry was performed using anti-histone H3.3G34W antibody in the diagnosed cases of GCTB (136 cases of GCTB from 133 patients, including two malignant GCTBs) and other giant cell-containing lesions (62 cases). The presence of unequivocal crisp nuclear staining was considered positive. Results: Immunohistochemistry revealed unequivocal nuclear positivity in the mononuclear cells in 87.3% of the cases of GCTB. Of these, most showed diffuse expression with moderate to strong intensity staining. The positive staining was restricted to the nuclei of mononuclear cells with the nuclei of osteoclastic giant cells being distinctly negative. In addition to conventional GCTBs, two cases each of multicentric and malignant GCTB showed positive staining. The other giant-cell containing lesions were distinctly negative. The present study showed a sensitivity of 87.3% with specificity and positive predictive value of 100%. Conclusion: The anti-histone G34W antibody is a highly sensitive and specific marker for the diagnosis of GCTB and differentiating it from its mimics. The positive staining is restricted to the mononuclear cell component of GCTB with sparing the osteoclastic giant cells further reiterating the fact that the mononuclear stromal cells are the true neoplastic component of GCTB.

Hepatic epithelioid hemangioendothelioma—report of three cases of a puzzling tumor

Hepatic epithelioid hemangioendothelioma (EHE) is a rare malignant vascular neoplasm with unpredictable clinical behavior. These lesions are frequently misdiagnosed owing to its non-specific symptomatology, ambiguous radiological features, and overlapping histomorphology. We report three cases of hepatic EHE, of which one was male and two were female patients. While all three patients presented with abdominal pain, the male patient gave an additional history of weight loss and was jaundiced. The radioimaging showed multiple nodules in the liver and two of the patients also had pulmonary metastasis. The biopsies of the liver nodules revealed a tumor composed of spindle, epithelioid, and stellate tumor cells, some with characteristic intracytoplasmic vacuolations/lumina surrounded by myxohyaline stroma. Some of these intracytoplasmic vacuoles/lumina showed erythrocytes, suggesting its vascular origin which was confirmed by CD31 and CD34 positivity. The article highlights the importance of histopathology and IHC in the precise diagnosis of EHE.

Pericardial mesothelioma presenting as chronic constrictive pericarditis. A series of three cases from a single institution

Pericardial mesotheliomas are rare tumors which often present with features of constrictive pericarditis. We present clinical, imaging, histological, and immunohistochemical findings of three cases presenting with chronic constrictive pericarditis. Two of these cases were initially treated as tuberculous pericarditis. Histologically, all the three cases were of an epithelioid type and showed positivity for more than one mesothelial markers. Two patients had a fatal outcome, and one was lost to follow-up.