[Articular and periarticular tumors : Important diagnoses in rheumatology and orthopedic rheumatology].

This review article presents the histopathological differential diagnostics of malignant and benign joint tumors as well as pseudotumors of the joints and the peri-implant tissue. Methodologically, these integrative diagnostics are based on conventional standard staining procedures, on immunohistochemical analyses of formalin-fixed and paraffin-embedded (FFPE) tissues and also on molecular diagnostic procedures, which can be particularly useful in the diagnosis of benign and malignant joint tumors. For joint tumors S100, smooth muscle (SM) actin, cluster of differentiation (CD) 68, CD34, signal transducer and activator of transcription (STAT) 6, clusterin, mucin 4 (Muc-4), beta-catenin and mouse double minute 2 homolog (MDM2) fluorescence in situ hybridization (FISH) are recommended. For the differential diagnostic typing of periarticular carcinoma metastases cytokeratin (CK, AE1/AE3), CK8, p63, thyroid transcription factor (TTF)-1, thyroglobin (TGB), prostate-specific antigen (PSA), androgen receptor, GATA, CD56, chromogranin, caudal type homeobox (CDX) 2, special AT-rich sequence-binding protein 2 (SATB2), spalt like transcription factor 4 (SALL4), estrogen and progesterone receptors, CD45LCA, CD30, CD79a and S100 are recommended. Necrosis, pronounced inflammatory infiltration and reparative inflammatory changes can make histopathological classification difficult. Therefore, the correlation with clinical, microbiological and radiological imaging data may be necessary in the sense of interdisciplinary integrative diagnostics. In the case of histopathological findings that reveal questionable representativeness, the report should definitely refer to the need for clinical or radiological control as well as the need for a second biopsy.