Sinonasal SMARCB1 (INI1) Deficient Carcinoma With Yolk Sac Tumor Differentiation: Report of a Case and Comparison With INI1 Expression in Gonadal Germ Cell Tumors.

SMARCB1 (INI1) deficient sinonasal carcinoma is a recently recognized entity with wide histomorphologic spectrum. We present a case of this carcinoma that contained, in addition to a "common" morphology, scattered foci of yolk sac tumor differentiation. The tumor occurred in paranasal sinuses in a 44-year-old woman. Immunohistochemically, it was diffusely negative for INI1, whereas an expression of yolk sac tumor markers (α-fetoprotein, glypican-3, CDX2) was limited to the yolk sac tumor component. For comparison with the present case, we performed INI1 immunostaining on a series of 11 gonadal germ cell tumors with yolk sac tumor differentiation. All of these cases showed strong and diffuse expression of INI1, in contrast with the present sinonasal tumor. Our findings expand the morphologic spectrum of SMARCB1 (INI1) deficient sinonasal carcinoma. In addition, we show preliminarily that gonadal germ cell tumors with yolk sac tumor differentiation are not SMARCB1/INI1-deficient.

Lymphocyte-rich renal cell carcinoma: an unusual histomorphologic manifestation of a tumor that is not part of lynch syndrome.

Lynch syndrome (LS) is characterized by familial clustering of early cancer development in various organs. One of the histologic characteristics of carcinomas associated with LS is prominent intratumoral and peritumoral lymphocytes. The relationship between LS and the rare lymphocyte-rich clear cell renal cell carcinoma (CRCC) has been not been studied. We compared lymphocyte-rich CRCC (N=15) with CRCC with no or minimal lymphoid infiltration, occurring in young (<40 y of age) patients (N=15) and in a control group of older (>62 y of age) patients (N=5) with CRCC having conventional histologic features. All cases were analyzed histologically and immunohistochemically using antibodies against the mismatch repair (MMR) proteins MLH1, MSH2, MSH6, and PMS2. The mutational status of the Von Hippel-Lindau (VHL) gene was analyzed successfully in 25 cases. We found no case with complete absence of immunoreactivity for the MMR proteins/ enzymes studied in any of the groups. Hence, none of the RCCs with heavy lymphocytic infiltration displayed complete absence of protein expression of any of the MMR enzymes. We found mutation of the VHL gene in 2 of 8 tumors from group A, in 4 of 12 tumors from group B, and no mutation in the control group C. We conclude that this rare subset of renal neoplasms is not part of the spectrum of tumors seen in LS. The results of the VHL gene analysis are in concordance with published data on sporadic CRCCs.

Metastatic desmoplastic malignant melanoma associated with low-grade myofibroblastic sarcoma.

The authors report a 63-year-old man with a 2-year history of a primary desmoplastic malignant melanoma on the right heel with lymph node metastasis in the right groin, presented with a large painless mass in the right inguinal area. Microscopically, there was a dense spindle cell proliferation in the reticular dermis, subcutis, and subjacent soft tissue. The neoplastic cells were moderately pleomorphic and showed mitotic figures including atypical ones. Immunohistochemical studies showed a biphasic cellular composition, with one component being S-100 protein positive and alpha-smooth muscle actin negative and another component with a reverse phenotype, namely, alpha-smooth muscle actin positive and S-100 protein negative. Pleomorphic cells and atypical mitotic figures were evident in both components. Electron microscopy identified cells with peripheral bundles of thin cytoplasmic myofilaments with focal dense bodies, fibronexus junctions, abundant rough endoplasmic reticulum, micropinocytic vesicles, and strikingly folded nuclei. These cells had features of myofibroblasts. We conclude that the myofibroblastic proliferation in this case clearly exceeded just a stromal reaction and fulfilled the criteria of a low-grade sarcoma.