Our results suggest that compared to final pathology, biopsy of small renal masses accurately informs an algorithm incorporating size and histological risk group that directs the management of small renal masses.

We illustrate a case of an inflammatory myofibroblastic tumor (IMT) involving the bladder in a woman with dysuria and review the literature and differential diagnosis. Inflammatory myofibroblastic tumor, also referred to as pseudosarcomatous myofibroblastic proliferation, is a rare lesion that can arise in the genitourinary system and is characterized by a fascicular arrangement of myofibroblasts with admixed inflammatory cells and slitlike vessels. Urinary bladder IMT can be a diagnostic pitfall because its histologic features (brisk mitoses, invasion into muscularis propria, and prominent nucleoli) can mimic malignancy. The differential diagnosis of urinary bladder IMT includes sarcomatoid carcinoma and leiomyosarcoma. Diagnostic features such as bland nuclear chromatin, ganglion-like cells, pale eosinophilic cytoplasm with long processes, overexpression of anaplastic lymphoma kinase (immunohistochemistry or gene rearrangement studies), and the absence of atypical mitoses help distinguish IMT from its malignant mimics. Current controversies regarding postoperative spindle cell nodule and IMT are discussed.

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PAX2 and PAX8 are transcription factors involved in embryogenesis that have been utilized as immunohistochemical indicators of tumor origin. Specifically, PAX2 is a marker of neoplasms of renal and müllerian origin, while PAX8 is expressed by renal, müllerian, and thyroid tumors. While studies examining these transcription factors in a variety of tumors have been published, data regarding their expression in salivary gland neoplasms are limited. The goal of this study was to assess expression of PAX2 and PAX8 in a large cohort of salivary gland tumors. Utilizing tissue microarrays, samples of normal salivary glands (n = 68) and benign and malignant salivary gland neoplasms (n = 442) were evaluated for nuclear immunoreactivity with PAX2 and PAX8. No expression was observed with either marker in the normal salivary glands, and PAX8 was negative in all neoplasms. Focal expression of PAX2 was observed in one example each of oncocytoma and acinic cell carcinoma. These results indicate that evaluation of PAX2 and/or PAX8 expression would be valuable in differentiating primary salivary gland tumors from metastases known to express PAX2 and/or PAX8.

Sarcomas, including rhabdomyosarcoma (RMS), are rarely encountered in effusion specimens; therefore, difficulties in the accurate diagnosis of metastatic sarcomas in effusions can occasionally arise. Immunohistochemistry for myogenin has emerged as a useful adjunct in the diagnosis of RMS, especially in small biopsy specimens. To date, there are no published series describing the utility of immunocytochemistry for myogenin in the diagnosis of RMS in effusion specimens. A total of 15 patients, for whom metastatic sarcomas were diagnosed in effusion specimens between 1998 and 2012, were identified for analysis: alveolar RMS (n = 5); embryonal RMS (n = 1); pleomorphic RMS (n = 1); angiosarcoma (n = 1); Ewing's sarcoma (n = 2); osteosarcoma (n = 1); endometrial stromal sarcoma (n = 1); unclassified spindle cell sarcoma (n = 1); unclassified/undifferentiated pleomorphic sarcoma (n = 1); and leiomyosarcoma (n = 1). Immunocytochemistry for myogenin was performed for each of these cases as well as for 102 effusions that were positive for metastatic carcinoma. Immunocytochemistry for myogenin diffusely and strongly highlighted the nuclei of the tumor cells in six (86%) of seven cases of metastatic RMS; specifically, the five alveolar RMS and one embryonal RMS cases. The one case of pleomorphic RMS, the eight remaining metastatic sarcoma cases, and all 102 cases of metastatic carcinoma were completely negative for myogenin expression. In conclusion, immunocytochemistry for myogenin is a sensitive and specific ancillary adjunct in the diagnostic evaluation of metastatic RMS in effusion specimens.

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