Discussion:

Urothelial carcinomas may rarely have focal areas showing rhabdoid features. The rhabdoid phenotype has characteristic histological, ultrastructural, immunohistochemical, and cytogenetic findings. Tumor cells are discohesive and are present either singly, in clusters, and/or in large sheets. This neoplasm demonstrates a characteristic morphology with large pleomorphic cells with large nuclei and nucleoli. There is abundant cytoplasm containing eosinophilic inclusions that are composed of intermediate filaments. The tumors generally have a histological appearance similar to that of renal rhabdoid tumors. Ultrastructural studies have confirmed that the eosinophilic body corresponds to whorls of intermediate filaments. Immunohistochemical analysis usually demonstrates reactivity to vimentin, desmin, and keratin. Extrarenal rhabdoid tumors do not demonstrate skeletal muscle components by immunohistochemical analysis or electron microscopy. Cytogenetic analyses of rhabdoid tumors in children have shown a balanced translocation involving the short arm of chromosome 6 (6p12) and the long arm of chromosome 22 (22q11). More recently, a candidate tumor suppressor gene for malignant rhabdoid tumors in children, INI1, has been described in the same location (22q11). The prognosis of urothelial carcinomas with glandular features is poor and is characterized by an aggressive clinical course.

Urothelial carcinoma of bladder demonstrates a capacity of divergent histologic differentiation, which contains 13 kinds of variable types and glandular differentiation is the second most common type Patients of urothelial carcinoma with glandular differentiation (UGCD) tend to have higher pathological grade and progression rate, which may indicate the aggressive clinical course. Urothelial carcinoma of bladder with more than one variant tended to have higher rate of lymphatic metastasis. The diagnosis of bladder pure adenocarcinoma should eliminate any elements of urothelial carcinoma. Grignon et al. recommend that classify a tumor with mixed glandular and urothelial differentiation as urothelial carcinoma with glandular differentiation regardless of the extent of the glandular differentiation. Recently, UCGD and bladder adenocarcinoma were considered two independent kinds of tumor and no relationships were found between them. Glandular tumor cells had variant shapes, which can be cubic or polygonous, forming tubular or enteric glands with mucin secretion. Light microscopic evaluation is key to identify glandular lesions, but occasionally, it is difficult to distinguish GD from conventional UC or adenocarcinoma, particularly in cases with unclear features. In this case, usage of immunohistochemical (IHC) markers are helpful for definite diagnosis. It was reported that MUC5A, MUC2, CK20, c-erbB2 were completely positively expressed in tumor cells of UCGD, meanwhile, MUC1, CK7, 34βE12 could also be the markers helping distinguishing similar cells.

The morphological resemblance of plasmacytoid urothelial carcinoma (PUC) to other malignancies is a source of diagnostic dilemmas and often misdiagnosis. Amongst the differential diagnosis for PUC ranging from benign to malignant lesions, common ones are cystitis with plasma cell infiltration along with plasma cell-derived neoplasms including large B-cell lymphomas and plasmacytomas, lymphomas, lymphoepitheliomas and metastatic carcinoma also are a source of diagnostic difficulties. Striking plasmacytoid morphology is seen in the metastatic disease from breast and stomach as well as melanoma and rhabdomyosarcoma and may pose a diagnostic challenge. Other neoplasms that may have plasmacytoid cells include medullary carcinoma, myoepithelial carcinoma, and carcinoid. Mucin-containing cells that may mimic true signet ring cells may be focally present in PUC. Prognosis of PUC is poor, a biopsy usually reveals a high-grade tumor infiltrating the lamina propria and muscularis, with high potential of metastasis and because of the rarity of the disease, the treatment is not well defined. However, since the majority of patients have advanced disease at diagnosis radical cystectomy and adjuvant chemotherapy is advise.