Modern Pathology最新文献

Tumors resembling tenosynovial giant cell tumor (TGCT) but additionally forming chondroid matrix are rare and most often involve the temporomandibular joint (TMJ). We studied 21 tumors consisting of synoviocytes (large, eosinophilic mononuclear cells containing hemosiderin) and chondroid matrix to better understand these unusual neoplasms. The tumors occurred in 10 males and 11 females, in the age group of 31 to 80 years (median, 50 years) and involved the TMJ region (16), extremities (4), and spine (1). As in conventional TGCT, all were composed of synoviocytes, small histiocytes, foamy macrophages, siderophages, and osteoclast-like giant cells in variably hyalinized background. Expansile nodules of large, moderately atypical synoviocytes were present, in addition to “chondroblastoma-like,” “chondroma-like,” or “phosphaturic mesenchymal tumor-like” calcified matrix. The synoviocytes expressed clusterin (17/19) and less often desmin (3/15). The tumors were frequently CSF1 positive by chromogenic in situ hybridization (8/13) but at best weakly positive for CSF1 by immunohistochemistry (0/3). Background small histiocytes were CD163 positive (12/12). All were FGF23 negative (0/10). Cells within lacunae showed a synoviocytic phenotype (clusterin positive; S100 protein and ERG negative). RNA-Seq was successful in 13 cases; fusions were present in 7 tumors, including FN1::TEK (5 cases); FN1::PRG4 (2 cases); and MALAT1::FN1, PDGFRA::USP35, and TIMP3::ZCCHC7 (1 case each). Three tumors contained more than 1 fusion (FN1::PRG4 with TIMP3::ZCCHC7, FN1::TEK with FN1::PRG4, and FN1::TEK with MALAT1::FN1). Clinical follow-up (17 patients; median follow-up duration 38 months; range 4-173 months) showed 13 (76%) to be alive without evidence of disease and 4 (24%) to be alive with persistent/recurrent local disease. No metastases or deaths from disease were observed. We conclude that these unusual tumors represent a distinct category of synoviocytic neoplasia, which we term “chondroid synoviocytic neoplasm,” rather than simply ordinary TGCT with cartilage. Despite potentially worrisome morphologic features, they appear to behave in at most a locally aggressive fashion.

Acral fibrochondromyxoid tumor (AFCMT) is a recently described likely benign mesenchymal neoplasm arising in the distal extremities with distinctive histologic features and a recurrent THBS1::ADGRF5 fusion. We studied an additional 37 cases of AFCMT and expanded on the so-far reported clinicopathologic and molecular findings. Tumors occurred in 21 females and 16 males, ranging in age from 17 to 78 years (median age: 47), and solely involved the hands (24/37, 65%) or feet (13/37, 35%). Histologic examination revealed well-delineated uni- or multinodular tumors with prominent vasculature-rich septa and bland, chondrocyte-like tumor cells set within abundant chondromyxoid stroma. Immunohistochemical studies showed that tumor cells were positive for CD34 (25/27; 93%) and ERG (27/27; 100%), whereas negative for S100 protein (0/31). Molecular analysis revealed evidence of a THBS1::ADGRF5 fusion in 17 of 19 (89%) successfully tested tumors. Clinical follow-up was available in 8 cases (median: 97 months), with multiple local recurrences in 1 case at 276, 312, and 360 months. We conclude that AFCMT is a distinct entity with reproducible morphologic, immunohistochemical, and molecular genetic features that should be differentiated from other similar appearing acral mesenchymal neoplasms.