Overview of histiocytic and dendritic disorders by the 5th version of WHO Classifi cation of Hematolymphoid Tumours from 2022.

BACKGROUND: Histiocytoses are rare disorders characterized by the accumulation of macrophages, dendritic cells, or monocyte-derived cells in various tissues and organs of children and adults, with a wide range of clinical manifestations, presentations, and histology. The histiocytoses are classified according to the WHO Classification, the last version of which was published in 2022, or according to the Histiocyte Society Classification, with the last version published in 2016. PURPOSE: This text provides an overview of histiocytoses as described in the WHO Classification 2022.

Monoclonal gammopathy of clinical signifi cance with osteosclerotic lesions - a case report and a literature review.

INTRODUCTION: Multiple myeloma is a common plasma cell neoplasia usually accompanied by the formation of osteolytic foci, whereas osteosclerotic myeloma is a very rare form of plasma cell dyscrasia. When osteosclerotic myeloma is detected, osteosclerotic foci are usually part of the POEMS syndrome. Osteosclerotic myeloma without other manifestations of the POEMS syndrome is an unusual finding. CASE DESCRIPTION: In a 46-year-old woman, osteosclerotic changes of the temporoparietal region caused soft tissue induration over this lesion, which initiated further investigation. Imaging studies subsequently showed multiple osteosclerotic foci in the skull. Examination of blood proteins revealed 8 g/L of IgG-lambda monoclonal immunoglobulin, subclass IgG1. In search of the cause of the osteosclerotic changes, FDG-PET/CT was performed, which revealed no FDG accumulation, i.e., no other tumor (breast or stomach cancer). Low-dose CT showed irregular bone structure, but not significant osteolytic or osteosclerotic foci. To map the extent of osteosclerotic changes, NaF-PET/CT imagination followed, which revealed multiple spots with high fluoride accumulation. A parietal bone biopsy showed osteosclerosis with minor clonal plasma cell infiltration. Trepanobioptic bone marrow sampling revealed an infiltration of bone marrow with atypical plasma cells in 8%. Flow-cytometric examination of bone marrow showed 0,37% of plasma cells, however predominantly (91%) clonal with lambda expression. MRI of the brain identified asymptomatic meningeal thickening. There was no evidence of POEMS syndrome in the patient; thus, we concluded the diagnosis as monoclonal gammopathy of clinical significance with osteosclerosis which was previously termed osteosclerotic multiple myeloma. CONCLUSION: Monoclonal gammopathy of clinical significance (MGCS) with osteosclerotic skeletal changes, documented on CT and multiple foci with intensive osteoneogenesis, documented on NaF-PET/CT without evidence of POEMS syndrome, is an extremely rare form of plasma cell dyscrasia. This publication documents the unique clinical manifestations of IgG-lambda type plasma cell proliferation without signs of POEMS syndrome and the role of NaF-PET/CT imaging. Classification of this disease as MGSC with osteosclerotic manifestations is more consistent with the indolent nature of the disease with a significantly better prognosis, compared with multiple myeloma.

Waldenström's macroglobulinemia - clinical symptoms and review of therapy yesterday, today and tomorrow.

BACKGROUND: Waldenström macroglobulinemia (WM) is a lymphoplasmocytic lymphoma with immunoglobulin M monoclonal protein. The incidence of this disease is very low (0.4/100,000), so that this disease can be regarded as an orphan's disease. It means that new drugs are often tested and registered for more frequent diseases. PURPOSE: In this review we will focus on the efficacy of the new drugs for WM. RESULTS: The current treatment options for symptomatic WM patients include alkylating agent cyclophosphamide and anti-CD20 monoclonal antibodies. Therapy with rituximab and bendamustin resulted in longer therapeutic response then therapy with rituximab, cyclophosphamide and dexamethasone. Many drugs, used in multiple myeloma (MM), shoved promising results in WM patients. Bortezomib is effective in WM, but its neurotoxicity is higher in WM than in MM patients. Therefore, new proteasome inhibitors, carfilzomib and ixazomib, are better tolerated as documented in several studies. New types of antiCD20 antibody (obinutuzumab) can be used in patients with rituximab intolerance. in five of our patients with WM, obinutuzumab and bendamustin reached deeper responses than therapies administered in previous lines of therapy. Oral Bruton tyrosine kinase (BTK) inhibitor ibrutinib alone and in combination with rituximab have extended the treatment options for WM patients. New BTK inhibitors (e. g. acalabrutinib, zanubrutinib, and vecabrutinib) were tested and their lower toxicity (atrial fibrillation) was documented. Moreover, the BCL2 inhibitor venetoclax is newly tested. CONCLUSION: New antiCD20 antibody (obinutuzumab) is of advantage in patients with WM with rituximab intolerance as well as bendamustin and new proteasome inhibitors (ixazomib and carfilzomib) or new BTK inhibitors with lower cardiotoxicity. Many of the abovementioned drugs do not have official registration for WM and can be administrated with the consent of the health care provider only. Thus, this work brings evidence of their efficacy.