Introduction: In healthy adult kidneys, differentiated tubular epithelial cells do not express the neural cell adhesion molecule (NCAM), while a small number of NCAM-expressing cells can be detected in the renal interstitium. The role and the significance of these cells have not yet been clarified, but it has been observed that the number of NCAM-expressing cells increases in the initial stage of interstitial fibrosis. Aim: The aim of the study is to examine the significance of the expression of NCAM molecules in the renal interstitium, in etiologically different diseases, with varying degrees of interstitial fibrosis, as well as to define the pathohistological and clinical indicators (predictors) of impaired kidney function. Materials and methods: The study included 69 patients who underwent needle biopsies of the kidneys in 2011 and 2012. Clinical and laboratory data were collected at the time of the biopsy and at the time of the latest follow-up examination. Pathohistological characteristics were defined optically-microscopically, while NCAM-expressing interstitial cells were detected with immunohistochemical staining, using the primary NCAM antibody (1:50, clone 123C3.D5). Results: NCAM-expressing interstitial cells were detected in 59.4% of kidney biopsies, the presence of these cells was significantly more frequent in the initial stages of interstitial fibrosis than in the remaining stages (p < 0.001), and it did not depend on the pathohistological diagnosis (p = 0.995). Patients in whom NCAM cells were detected had significantly lower proteinuria levels at the time of biopsy, as compared to patients without NCAM interstitial cells (p = 0.024). The levels of serum creatinine (p < 0.001) and urea (p = 0.007) significantly influenced the probability of the deterioration of renal function. Conclusion: The presence of NCAM cells in the kidney interstitium is a characteristic of the early stages of chronic kidney disease with incipient interstitial fibrosis and a lesser degree of proteinuria

Introduction/Aim: Membranous nephropathy (MN) typically presents as nephrotic syndrome and may be idiopathic (primary MN, pMN) or occur secondary to other diseases (secondary MN, sMN). Given the differing therapeutic approaches, this study aimed to compare clinical and pathohistological parameters between patients with pMN and sMN. Methods: Through a retrospective analysis of kidney biopsy samples diagnosed at the Institute of Pathology, Faculty of Medicine, Belgrade, between 2011 and 2023, 99 patients with membranous nephropathy were identified. These patients were divided into two groups: patients with pMN (n = 44) and patients with sMN (n = 55). Clinical and pathohistological parameters (by optical and immunofluorescence microscopy) were compared among study participants. Results: While males more frequently suffered from MN, females more frequently had sMN (p = 0.036). Haematuria was more common in subjects with sMN (p = 0.009). Proteinuria values were significantly higher among patients with pMN (p = 0.018), related to a significantly greater decrease in serum total protein values in them (p = 0.011). Endocapillary proliferation was significantly more frequent among those with sMN (p = 0.032). Marked positivity of several immunofluorescent markers was significantly more common in subjects with sMN: IgA, IgM, C1q, κ-chains, and λ-chains (p < 0.05). Conclusion: Females are more commonly affected by sMN. Characteristics of sMN include presence of haematuria, endocapillary hypercellularity and immunofluorescence positivity for markers not seen in pMN (IgA, IgM, C1q), while characteristics of pMN include significantly higher levels of proteinuria, accompanied by significantly reduced serum protein values.

Multiphoton microscopy (MPM) is a cutting-edge nonlinear microscopy technique known for its exceptional capabilities in imaging dense tissues, making it an ideal tool for exploring human kidney tissue. This study delves into the application of MPM in evaluating renal cell tumors and characterizing tumor capsules. MPM encompasses two core methods: two-photon excitation fluorescence (TPEF) and second harmonic generation (SHG). It leverages femtosecond lasers to provide deep tissue imaging while minimizing phototoxicity, making it well-suited for live tissue analysis. The study analyzed 100 formalin-fixed paraffin-embedded (FFPE) kidney tissue samples, ensuring compliance with ethical standards. Using a Ti:Sapphire laser for femtosecond pulses and a variety of optical components and filters, the researchers captured TPEF and SHG signals, facilitating image analysis. Normal kidney tissue exhibited distinctive structures like glomeruli and tubules under MPM. Renal cell carcinoma (ccRCC) displayed unique TPEF patterns with eccentrically located nuclei and indistinct cytoplasmic membranes. Papillary RCC (pRCC) exhibited a papillary pattern with dark nuclei, while chromophobe RCC (chRCC) showcased distinct features like thick cell membranes, strong TPEF signal in nuclei, and granular cytoplasm. Renal oncocytoma (RO) presented strong TPEF signals in cuboidal cells with microcyst-like arrangements. Overall, MPM proved invaluable in assessing human kidney tissue, offering distinct TPEF patterns for different renal cell tumor types. This non-invasive technique has the potential to enhance pathological examinations and advance our understanding of complex biological processes, ultimately contributing to improved diagnostics and treatment strategies for renal diseases.

Introduction: Widespread routine ultrasound diagnostics enables early detection of kidney tumors. However, due to nonspecific symptomatology and signs that usually appear as the disease progresses, there are still patients whose diagnosis is made only in advanced stages of the disease. Aim: Our aim was to investigate the correlation of human epididymis protein 4 (HE4) expression, including the intensity and localization of HE4 positivity, with the clinical and pathohistological characteristics of kidney tumors. Material and Methods: The study included 96 kidney tumors diagnosed between 2010 and 2013 at the Institute of Pathology in Belgrade. Anti-HE4 antibodies were used for immunohistochemical analysis. Demographic, clinical, and pathohistological characteristics were examined in relation to HE4 expression. Results: No correlation was observed between HE4 expression in kidney tumors and patients' gender and the nuclear grade of tumors. However, HE4 expression was significantly more frequent in larger tumors, specifically in T3 and T4 tumors, compared to T1 and T2 tumors (p=0.009; p=0.006, respectively). No correlation was observed between HE4 expression and the pathohistological type of kidney tumors, but it is important to emphasize that membrane expression of HE4, unlike most renal cell carcinomas, was not observed in oncocytomas. Conclusion: It's possible that HE4 plays a role in progression of kidney tumor growth. Membrane expression of HE4 could be used as a new parameter in differentiating renal cell carcinomas from oncocytomas.

Crohn’s disease (CD) is a chronic inflammatory bowel condition with increasing global incidence. Diagnosing CD is challenging and requires close collaboration between clinicians and pathologists due to the lack of specific diagnostic criteria. Histologically, CD is characterized by transmural inflammation, crypt distortion, metaplasia, and granulomas, although granulomas are not always present. Schaumann bodies (SB), initially described in sarcoidosis, are rare in CD but have been reported in about 10% of cases. This case report presents a 4-year-old female with chronic hemorrhagic diarrhea, severe anemia, and elevated inflammatory markers. Endoscopic and histological evaluations suggested CD, with the presence of SB in the gastric mucosa. Further investigations ruled out sarcoidosis, confirming a diagnosis of multi-segmental, very early onset CD with atypical histological features. SB are inclusions composed of calcium carbonate crystals and conchoid bodies, typically found within giant cells. The presence of SB in the mucosa is rare, limiting their diagnostic significance in endoscopic biopsies. Differential diagnosis should exclude other granulomatous diseases such as intestinal tuberculosis and sarcoidosis. This case highlights the importance of considering SB in the diagnosis of CD, particularly in pediatric patients.