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Objectives. Desmoplastic small round cell tumor (DSRCT) is an aggressive round cell sarcoma that arises in the abdominal cavity/pelvis of young males. We sought to expand its clinicopathologic spectrum. Methods. Cases of DSRCT presenting in patients >30 years of age or tumors arising outside of the abdominal cavity/pelvis were retrieved. Results. Thirtyfour cases were identified. Sixteen tumors arose at atypical sites (head/neck, intracranial, thigh, axilla/shoulder, inguinal/ paratesticular, intraosseous, and uterine corpus). The remaining 18 patients were older than 30 years, and their tumors involved the abdomen or pelvis. The majority of cases showed areas with classic histology, while 6 cases exhibited solid growth and 5 showed macronodular architecture. Cytologic appearance included round cell, rhabdoid, epithelioid, and small cell. Conclusion. DSRCT may arise at nonabdominal locations in both pediatric and adult populations, as well as intra-abdominally in older adults, and these tumors exhibit high rates of metastasis and morbidity.

Sarcomatoid melanoma is a rare type of melanoma lacking typical histologic features of melanoma and often lacks expression of S100 protein and melanocyte-specific markers. Given the rarity of this entity, its clinicopathologic findings are not well defined. We report 2 cases of sarcomatoid melanoma received in consultation: a 65-year-old woman with a right breast mass and a 62-year-old man with a left plantar heel mass. Both lesions were ulcerated, pedunculated, highly cellular proliferations of atypical spindle cells arranged as fascicles and/or sheets. The tumor cells of the breast mass expressed CD10 and vimentin diffusely but S100 protein only focally. The tumor cells of the heel mass lacked expression of melanocytic markers altogether, except for weak, very focal S100 protein expression. At the junctional edge of the breast mass and in the ulcer base of the heel mass, focal precursor melanoma was present and exhibited melanocytic differentiation. We report these cases to emphasize the importance of meticulous histologic inspection at the lesion's edge and/or ulcer base to correctly identify the conventional precursor melanoma in these rare lesions to ensure appropriate diagnosis and subsequent clinical management as treatment options may be significantly different from those offered for sarcomas.

We recently encountered a case of primary pulmonary angiomatoid fibrous histiocytoma (AFH), which was initially misdiagnosed as inflammatory myofibroblastic tumor (IMT) based in part on anaplastic lymphoma kinase (ALK) expression by immunohistochemistry (IHC). Prompted by this experience, we evaluated ALK expression in 11 AFH, 15 IMT, and 11 follicular dendritic cell sarcomas using 3 different antibody clones: D5F3, 5A4, and ALK1. ALK IHC positive cases were analyzed with fluorescence in situ hybridization (FISH) using dual color ALK break-apart probe kit. The majority of AFH cases studied were positive for ALK IHC with at least 1 antibody (9/11 D5F3, 6/9 5A4, 1/9 ALK1), most demonstrating moderate to strong cytoplasmic staining. AFH with positive ALK IHC showed no ALK gene rearrangement by FISH (0/8) with ALK copy number ranging from 1.6 to 2.1. Sixty-seven percent of IMT were ALK positive by IHC (10/15 D5F3, 8/15 5A4, 7/15 ALK1), and 9 of the 10 cases were positive for ALK gene rearrangement by FISH. All follicular dendritic cell sarcomas were negative for ALK by IHC (D5F3 and 5A4). Our results indicate that ALK expression in AFH is common, particularly with the highly sensitive D5F3 and 5A4 antibodies and enhanced detection systems, and may be a potential source of diagnostic confusion with IMT. The underlying mechanism of ALK expression in AFH is unclear, although it does not appear to be from ALK rearrangement or amplification.

Due to an unusual anatomical location and frequent infiltration of skeletal muscle, spindle cell/pleomorphic lipoma of the face can be a difficult diagnosis. Increased awareness of its clinicopathological features should allow accurate classification.

We assessed the frequency of programmed death-ligand 1 (PD-L1) expression by immunohistochemistry (IHC) in a cohort of 522 sarcomas from 457 patients, incuding a subset of 46 patients with 63 matched samples from local recurrence or metastases with primary tumours and/or metachronous metastases. We also investigated the correlation of PD-L1 with the presence and degree of tumour-infiltrating lymphocytes (TILs) in a subset of cases. IHC was performed using the PD-L1 SP263 companion kit (VENTANA) on tissue microarrays from an archival cohort. Evaluation of PD-L1 and TILs was performed on full sections for a subset of 23 cases. Fisher's exact and Mann Whitney test were used to establish significance (P <0.05). PD-L1 positive expression (�1%) was identified in 31% of undifferentiated pleomorphic sarcomas, 29% of angiosarcomas, 26% of rhabdomyosarcomas, 18% of myxofibrosarcomas, 11% of leiomyosarcomas and 10% of dedifferentiated liposarcomas. Negative expression was present in all atypical lipomatous tumous/well-differentiated lipoasarcomas, myxoid liposarcomas, synovial sarcomas, pleomorphic liposarcomas, and Ewing sarcomas. PD-L1 IHC was concordant in 81% (38 of 47) of matched/paired samples. PD-L1 IHC was discordant in 19% (9 of 47 matched/paired samples), displaying differences in the proportion of cells expressing PD-L1 amongst paired samples with the percentage of PD-L1-positive cells increasing in the metastatic/recurrent site compared to the primary in 6 of 9 cases (67%). Significant correlation between PD-L1 expression and the degree of TILs was exclusively identified in the general cohort of leiomyosarcomas, but not in other sarcoma subtypes or in metastatic/recurrent samples. We conclude that the prevalence of PD-L1 expression in selected sarcomas is variable and likely to be clone dependent. Importantly, we demonstrated that PD-L1 can objectively increase in a small proportion of metastases/recurrent sarcomas, offering the potential of treatment benefit to immune checkpoint inhibitors in this metastatic setting. PLOS ONEPLOS ONE | https://doi.org/10.1371/journal.pone.0222551 April 15, 2020 1 / 17 OPEN ACCESS Citation: Vargas AC, Maclean FM, Sioson L, Tran D, Bonar F, Mahar A, et al. (2020) Prevalence of PD-L1 expression in matched recurrent and/or metastatic sarcoma samples and in a range of selected sarcomas subtypes. PLoS ONE 15(4): e0222551. https://doi.org/10.

Head and neck clear cell sarcoma is rare but should be considered in the differential diagnosis of nested tumors with fibrous septae. Molecular analysis should be considered for definitive diagnosis regardless of location.

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