Feline giant-cell pleomorphic sarcoma: cytologic, histologic and immunohistochemical characterization

Abstract

Objectives This study aimed to characterize the cytologic, pathologic and immunohistochemical (IHC) aspects of feline giant-cell sarcoma. Methods Biopsy and necropsy reports from the Department of Veterinary Pathology were retrieved, and 13 cases of pleomorphic sarcoma (PS) were selected according to the established epidemiologic, pathologic and IHC criteria. All samples were fixed in 10% formalin, routinely processed for histology, and stained with hematoxylin and eosin. Samples also underwent IHC testing for vimentin, ionized calcium-binding adaptor molecule 1 (Iba-1), desmin, actin and S-100. Results The mean age of the affected cats was 9.5 years, and females were over-represented. Most neoplasms were observed in the flank, lateral thorax, limbs and interscapular region, and were >2 cm in diameter. Cytology analysis revealed highly cellular preparations with three distinct populations (spindle cells, small round cells and multinucleated giant cells) in a dense eosinophilic stroma. Histologically, PS was composed of a combination of these three populations. IHC labeling for vimentin and Iba-1 was strongly positive for spindle cells and multinucleated giant cells, respectively. Desmin/actin showed variable labeling among the samples. S-100 was negative in all samples. Conclusions and relevance PS is a neoplasm of mesenchymal origin, also known as malignant fibrous histiocytoma. The predominant subtype in this study that affected the cats was the giant-cell type, characterized by the presence of multinucleated giant cells among spindle-shaped cells. These findings are similar to those described in human patients; thus, a comparison between the neoplasms seen in these species might be useful, and the knowledge of biologic behavior and overall treatment approach for humans could be extrapolated to cats.

Primary diaphragmatic undifferentiated pleomorphic sarcoma in a cat

“… 8 – 10 In our case, rare histiocytoid cells and multinucleated giant cells were weakly positive and all the spindle neoplastic cells were negative; for this reason, a diagnosis of HS was ruled out. Similar results were reported by De Cecco et al, 7 who described 13 cases of feline pleomorphic sarcoma, in which the labelling for Iba-1 was mild to marked in histiocytoid cells and multinucleated giant cells, while the spindle cells were negative. It is not clear if histiocytoid and giant cells have neoplastic or inflammatory behaviour in undifferentiated pleomorphic sarcoma; in fact, both antibodies (CD18 and Iba-1) mark neoplastic, as well as non-neoplastic, cells.…”

“…It is not clear if histiocytoid and giant cells have neoplastic or inflammatory behaviour in undifferentiated pleomorphic sarcoma; in fact, both antibodies (CD18 and Iba-1) mark neoplastic, as well as non-neoplastic, cells. 8 In some of the cases described by De Cecco et al, 7 spindle cells were negative for antibodies against α-SMA and desmin, as in the case described herein. In other cases, the spindle cells were positive to antibodies against α-SMA and desmin, suggesting a fibroblastic/myofibroblastic phenotype.…”

“…The diagnosed histotype was a feline undifferentiated pleomorphic sarcoma (or anaplastic sarcoma with giant cells), which is an uncommon tumour of the skin and subcutaneous tissue, usually affecting middle-aged to old animals (mean age 9.5 years). 7 Undifferentiated pleomorphic sarcoma, previously known as malignant fibrous histiocytoma or anaplastic sarcoma with giant cells, is a still controversial entity in human and veterinary medicine; 8,9 in our case, the histological variant was 'giant cell', with numerous giant cells and many spindle cells (fibroblast/myofibroblastlike) and very few mononuclear histiocytoid cells. Histiocytic sarcoma (HS) is the main differential diagnosis to consider; in our case, both the morphological aspect and the immunohistochemical results were not compatible with a HS.…”

“…The diagnosed histotype was a feline undifferentiated pleomorphic sarcoma (or anaplastic sarcoma with giant cells), which is an uncommon tumour of the skin and subcutaneous tissue, usually affecting middle-aged to old animals (mean age 9.5 years). 7 …”

“…Feline pleomorphic sarcomas have been described in several anatomical locations, including the dermis and subcutis in non-vaccine sites. 8 Cytological, pathological and immunohistochemical characteristics have also been described, while treatment, prognosis and outcome have not been extensively characterised, 7 even if the expected outcome is possibly similar to other soft tissue sarcomas, characterised by local invasiveness and a low-to-moderate metastatic rate.…”