Xp11.2 translocation carcinoma is a distinct subtype of renal cell carcinoma characterized by translocations involving the TFE3 gene. Our study included the morphological, immunohistochemical and clinicopathological examination of 28 Xp11.2 RCCs. The immunophenotype has been assessed by using CA9, CK7, CD10, AMACR, MelanA, HMB45, Cathepsin K and TFE3 immunostainings. The diagnosis was confirmed by TFE3 break-apart FISH in 25 cases. The ages of 13 male and 15 female patients, without underlying renal disease or having undergone chemotherapy ranged from 8 to 72. The mean size of the tumors was 78.5 mm. Forty-three percent of patients were diagnosed in the pT3/pT4 stage with distant metastasis in 6 cases. Histological appearance was branching-papillary composed of clear cells with voluminous cytoplasm in 13 and variable in 15 cases, including one tumor with anaplastic carcinoma and another with rhabdoid morphology. Three tumors were labeled with CA9, while CK7 was negative in all cases. Diffuse CD10 reaction was observed in 17 tumors and diffuse AMACR positivity was described in 14 tumors. The expression of melanocytic markers and Cathepsin K were seen only in 7 and 6 cases, respectively. TFE3 immunohistochemistry displayed a positive reaction in 26/28 samples. TFE3 rearrangement was detected in all the analyzed cases (25/25), including one with the loss of the entire labeled break-point region. The follow-up time ranged from 2 to 300 months, with 7 cancer-related deaths. In summary, Xp11.2 carcinoma is an uncommon form of renal cell carcinoma with a variable histomorphology and rather aggressive clinical course.

The renal angiomyolipoma (AML) is a benign tumor characteristically composed of fat, smooth muscle tissue, and vessels. We collected AMLs from our nephrectomy database, reclassified them according to their histological appearance, recorded the demographic, clinical, and pathological parameters, and compared them with oncocytoma (RO) and renal cell carcinoma (RCC). Immunohistochemistry was ordered in 41 cases. In 2224 nephrectomies, we found 52 AMLs with a 53 mm median size. The mean age was 52.76. Forty-eight tumors were sporadic, while four were hereditary. The revision resulted in 31 classic, 13 leiomyoma-like, five lipoma-like, two epithelioid, and one AML with epithelial cysts. SMA was diffusely positive, except for the epithelioid type, while MelanA harbored stronger expression than HMB45. AML was more frequent in females and appeared ten and 7 years earlier than RO and RCC, respectively. The follow-up time was 7.42 years, and neither tumor-related death nor relapse occurred. AML is rare in nephrectomies and develops primarily in females in their 50s with an average size of 50–60 mm at the surgery. The histological appearance in order of frequency is classic, leiomyoma-like, lipoma-like, epithelioid, and cystic. The MelanA, HMB45, and SMA immunohistochemistry can support the light-microscopic findings.

The lack of oestrogen receptor, progesterone receptor and human epidermal growth factor receptor-2 expression in breast cancer (BC) is the basis for the categorization of the tumour as triple negative breast carcinoma (TNBC). The majority of TNBCs are aggressive tumours with common metastases and decreased expression of markers that could help in identifying the metastatic lesion as of mammary origin. Breast markers, such as gross cystic disease fluid protein-15 (GCDPF-15), GATA binding protein 3 (GATA3), mammaglobin (MGB) and SOX10, are not uniquely specific to BC. Our aim was to evaluate trichorhinophalangeal syndrome type 1 (TRPS1) protein as a breast marker in a series of cytokeratin-5-expressing TNBC, mostly corresponding to basal-like TNBCs, previously characterized for the expression of other breast markers. One hundred seventeen TNBCs in tissue microarrays were immunostained for TRPS1. The cut-off for positivity was ≥ 10%. The reproducibility of this classification was also assessed. TRPS1 positivity was detected in 92/117 (79%) cases, and this exceeded the expression of previously tested markers like SOX10 82 (70%), GATA3 11 (9%), MGB 10 (9%) and GCDFP-15 7 (6%). Of the 25 TRPS1-negative cases, 11 were positive with SOX10, whereas 5 to 6 dual negatives displayed positivity for the other makers. The evaluation showed substantial agreement. Of the five markers compared, TRPS1 seems the most sensitive marker for the mammary origin of CK5-expressing TNBCs. Cases that are negative are most often labelled with SOX10, and the remainder may still demonstrate positivity for any of the 3 other markers. TRPS1 has a place in breast marker panels.

Low-grade oncocytic tumor (LOT) of the kidney is a recently recognized renal neoplasm with distinctive morphologic, immunophenotypic, and molecular features that distinguish it from other eosinophilic tumors such as oncocytoma and chromophobe renal cell carcinoma (chRCC). This study presents a comprehensive analysis of 20 LOTs from 19 patients, integrating clinicopathological, immunohistochemical, and genetic data. LOTs typically appeared as small, unilateral, well-circumscribed tumors with a tan-brown cut surface, composed of uniform eosinophilic cells with round nuclei and occasional perinuclear halos. Key histological hallmarks included an extensive capillary network and central edematous areas without necrosis or significant atypia. Immunohistochemically, all tumors showed strong diffuse CK7 positivity and CD117 negativity, with universal expression of GATA3, GPNMB, and L1CAM. Whole-exome and panel-based sequencing revealed recurrent mutations in the mTOR signaling pathway, including MTOR, TSC1, and ATM genes. mTORC1 activation was confirmed immunohistochemically in one case. No evidence of aggressive behavior or metastasis was observed during the follow-up period (median: 4.5 years). Comparative analysis demonstrated that LOT patients were diagnosed at an older age than those with chRCC and had smaller tumors overall. This study reinforces the notion that LOT is a distinct renal tumor entity with consistent morphology, immunoprofile, and mTOR-pathway-related genetic alterations. Despite overlapping features with other eosinophilic renal neoplasms, the specific immunohistochemical profile and indolent clinical course support LOT’s classification as a unique diagnostic category.

Chromophobe renal cell carcinoma (CHRCC) is known for morphologic variability. Besides classic morphology, several other patterns like pigmented adenomatoid, multicystic, even papillary were documented. 10 cases of CHRCC composed of small cell population in various percentages that were analysed using morphologic parameters, immunohistochemistry and next generation sequencing. Patients were 5 males and 5 females with 40-78 age range. Size of tumors ranged from 2.2 cm to 11 cm (mean 5.17 cm). Small cell component comprised 10-80% of total tumor volume, the rest was formed by cells with classic morphology. Immunohistochemical profile followed typical CHRCC immunophenotype with positivity for CD117, CK7 among others. Neuroendocrine markers were negative. Mutations of 13 genes were found: DCIER1, FGFR3, JAK3, SUFO, FAM46C, FANCG, MET, PLCG2, APC, POLE, EPICAM, MUTYH, AR. However, only mutation of PLCG2 is listed as pathogenic. Recognition of small cell variant of CHRCC is not problematic in tumors, where “classic” CHRCC component is present. In limited material, like core biopsy, recognising this pattern could be troublesome. Very problematic might be in limited material like core biopsy. From our limited data it seems, that small cell morphology has no influence on prognosis.