Perivascular epithelioid cell neoplasms (PEComas) include the common renal angiomyolipoma, pulmonary clear cell sugar tumor, lymphangioleiomyomatosis, and less common neoplasms of soft tissue, gynecologic, and gastrointestinal tracts. Recently, aberrant immunoreactivity for TFE3 protein (a sensitive and specific marker of neoplasms harboring TFE3 gene fusions) has been reported in as many as 100% of PEComas; however, TFE3 gene status in these neoplasms has not been systematically investigated. We used a fluorescence in situ hybridization (FISH) break-apart assay to evaluate for evidence of TFE3 gene fusions in archival material from 29 PEComas. These cases included 2 earlier published TFE3 immunoreactive nonrenal PEComas, 14 additional nonrenal PEComas, and 13 renal angiomyolipomas with predominantly spindle or epithelioid morphology. Four nonrenal PEComas (mean patient age 24 y) showed TFE3 gene rearrangements by FISH, and all 4 of these showed strong positive (3+) TFE3 immunoreactivity using the original validated overnight incubation protocol. Two of these cases had adequate mRNA for RT-PCR analysis, but neither harbored the PSF-TFE3 gene fusion reported earlier in 1 PEComa. In addition, a lung metastasis of a uterine PEComa showed TFE3 gene amplification, an earlier unreported phenomenon. None of the other 24 PEComas (mean patient age 54 y) showed TFE3 gene alterations, though 4 exhibited moderate positive (2+) TFE3 immunoreactivity. In contrast, using an automated stainer, 2 of these 4 cases exhibited strong (3+) TFE3 immunoreactivity. All PEComas with TFE3 genetic alterations immunolabeled strongly for Cathepsin K, similar to other PEComas. In conclusion, a subset of lesions currently classified as PEComas harbors TFE3 gene fusions. Although numbers are small, distinctive features of these cases include a tendency to young age, the absence of association with tuberous sclerosis, predominant alveolar architecture and epithelioid cytology, minimal immunoreactivity for muscle markers, and strong (3+) TFE3 immunoreactivity. Despite significant morphologic and immunohistochemical overlap with other PEComas, PEComas harboring TFE3 gene fusions may represent a distinctive entity.

Glomus tumors are relatively uncommon clinically benign tumors. Malignant glomus tumors are rare, and only a small number develop metastatic foci. The usual location is deep dermis or subcutis, but it has been reported in various locations. A 55-year-old man presented with an incidentally found thyroid mass. Neck ultrasound showed a mass with a heterogeneous hypoechoic calcific mass in the right lobe. Right lobectomy specimen showed the 3.6-cm-sized calcified mass composed of sheets of uniform round to polygonal cells and intervening staghorn-shaped vessels. Occasional cellular atypism and necrosis with increased mitotic activity (up to 7 per 10 high-power fields) were found. Infiltration to the residual thyroid parenchyma, vessel, thyroidal capsule, and strap muscle was found. These tumor cells were strongly positive for smooth muscle actin, collagen type IV, and vimentin with pericellular reticulin-cuffing. Ultrastructurally, closely packed oval-shaped tumor cells having cytoplasmic mitochondria, rough endoplasmic reticulums with pinocytotic vesicles along the plasmalemmal surface and thin filaments of 6 nm in diameter were surrounded by thick basal lamina. That mass was diagnosed as a malignant glomus tumor. Incidentally, a 0.5-cm-sized papillary carcinoma was found through entire embedding. Complete thyroidectomy with chemotherapy was done. Thirty months later, multiple metastases developed in the brain and lung, and he expired. To our knowledge, neither benign nor malignant thyroid glomus tumor has been previously described. Here, we describe the first case of a malignant glomus tumor in the thyroid gland.

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Rice body formation in a joint or bursa is a rare condition, and is usually associated with rheumatoid arthritis or tuberculous arthritis. Here we describe a case of multiple rice body formation in a shoulder joint and in adjacent bursae, which was confirmed to be due to septic arthritis by Candida species. To the best of our knowledge, rice body formation in Candida septic arthritis in an immune-competent patient has not been previously reported.