MED15::ATF1-Rearranged Tumor: A Novel Cutaneous Tumor With Melanocytic Differentiation.

We recently described novel dermal tumors with melanocytic differentiation and morphologic and biological similarities to cutaneous clear cell sarcoma, including CRTC1::TRIM11 cutaneous tumor, and clear cell tumors with melanocytic differentiation and either ACTIN::MITF or MITF::CREM. Here, we describe a series of 3 patients presenting with tumors reminiscent of CRTC1::TRIM11 cutaneous tumor, found to demonstrate a novel MED15::ATF1 fusion. All 3 patients were children (5-16 years old). Primary excision of case 1 showed a circumscribed wedge-shaped silhouette with peripheral intercalation into collagen fibers and scattered lymphoid aggregates. All 3 tumors abutted the epidermis; one showed a junctional component. Tumors were highly cellular and comprised of monomorphic, oval-to-round epithelioid cells arranged in vague nests and short fascicles in variably fibrotic stroma. Mitotic rate was high (hotspot 6-12/mm2), without atypical mitoses. Necrosis was focally present in case 3. All cases showed strong, diffuse nuclear staining for SOX10 and MITF (2/2) but showed variable expression for S100 protein (1/3) and other melanocytic markers-Melan-A (focal in 2/3), HMB45 (focal in 1/3), and Pan-Melanoma (patchy in 1/1). Whole-exome RNA sequencing demonstrated a MED15::ATF1 fusion without any other notable alterations. Cases 1 and 2 were completely excised without recurrence (12 months). Case 3 developed a grossly apparent regional lymph node spread shortly after primary biopsy. The patient was treated with wide excision, radiation, cervical lymph node dissection (4/46 with >75% lymph node replacement), and neoadjuvant and adjuvant nivolumab (alive without disease at cycle 11). This series is presented to aid in future diagnosis of this novel dermal tumor with melanocytic differentiation and emphasize the potential for aggressive biologic behavior, which should be considered in patient management planning.

Clear cell sarcoma of kidney: morphoproteomic analysis reveals genomic correlates and therapeutic options.

We used the morphoproteomic approach to analyze clear cell sarcoma of kidney (CCSK), a rare pediatric renal tumor, for which the exact pathogenesis and reliable diagnostic markers remain inexplicable. The tumor, currently being treated with chemotherapy and radiation therapy before or after radical nephrectomy, has demonstrated improved survival rates after introduction of doxorubicin. Three cases of CCSK were studied. We attempted to decipher the possible pathological mechanisms involved in CCSK and to explore the therapeutic targets and plausible less-toxic chemotherapeutic agents. We propose that cyclin D1 may be a central molecule in the pathogenesis of CCSK, driven mainly by the sonic hedgehog and the nuclear factor-kappa B pathways and secondarily by the mammalian target of rapamycin complex mTORC2/PI3K/Akt pathway, heat shock protein 90, and possibly phospholipase D1. Inclusion of relatively less toxic but effective therapies in the form of statins, 13-cis retinoic acid, curcumin, and 17-AAG in the combinatorial treatment strategies, which can target the involved subcellular pathways, may be considered.