case_images: PMC8569467_01
case_images: Image of the primary mass located on the left lateral elbow obtained approximately 1 month prior to presentation. Note the overlying alopecia and discoloration of the skin.
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case_images: PMC8569467_01_fvets-08-666226-g0001.jpg
case_images: F1
case_images: Physical examination identified a semi-fixed, 6 cm, raised cutaneous mass (Figure 1). Additionally, the left prescapular and axillary lymph nodes were firm and enlarged on palpation, measuring 4.4 and 2.9 cm in diameter, respectively (Figure 1).
case_images: Representative photomicrographs of a fine-needle aspirates from the left elbow mass (A) and the left prescapular lymph node (B,C), modified Wright-Giemsa stain. (A) The cytology image shows a population of neoplastic cells found in tight aggregates and occasionally individually. The neoplastic cells often contained eosinophilic material within the cytoplasm, x100. (B) There is a population of neoplastic cells that are cytologically similar to the population seen in the left elbow mass, x 20. (C) The neoplastic cells occasionally were seen individually and exhibited a spindloid appearance, x 100.
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case_images: PMC8569467_01_fvets-08-666226-g0002.jpg
case_images: F2
case_images: Multiple clusters of epithelial cells frequently containing intracellular, eosinophilic secretory material were found in acinar formations, which was suggestive of a glandular neoplasm (Figure 2). Occasional spindle-shaped neoplastic cells were observed (Figure 2).
case_images: Microscopic features of the neoplastic population, hematoxylin and eosin (H&E). (A) The neoplastic population is centered within the deep dermis but invades overlying mid to superficial dermis in multiple areas (asterisks), x 20 magnification. (B) There are solid aggregates of neoplastic cells along with occasional individualized cells (arrowhead) located within endothelium-lined (arrow) vascular profiles, x 40 magnification. (C) The majority of the neoplasm consist of disorganized sheets of pleomorphic, plump, epithelioid cells with moderate mitotic activity (arrow); intercellular channels are mostly compressed (arrowhead), but occasionally contain erythrocytes (asterisk), 40 x magnification. (D) Scattered throughout the neoplasm, there are regions with delicate, anastomosing, hyaline eosinophilic trabeculae lined by relatively flattened endothelial cells forming rete-like vascular profiles, x 60 magnification.
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case_images: PMC8569467_01_fvets-08-666226-g0003.jpg
case_images: F3
case_images: In the amputation specimen, the deep dermis contained an unencapsulated, locally invasive, malignant mesenchymal population forming expansile nodules with random intervening bands of collagen, multifocal central tumor necrosis, and reactive mixed inflammation (Figure 3A). Cells were supported by, and often encircled, narrow to thick eosinophilic trabeculae (wrap-around cells), forming a meshwork of vascular channels containing variable numbers of erythrocytes, leukocytes, and individualized neoplastic cells (Figure 3B). Many regions of the neoplasm were devoid of erythrocytes, appearing instead as disorganized sheets of neoplastic cells intermixed with empty, narrow clefts and channels (Figure 3C). Occasionally, the vascular profiles within the neoplasm exhibited distinct retiform architecture (Figure 3D).
case_images: Immunohistochemical staining of representative tissue sections from the primary mass. Positive cytoplasmic/membranous labeling was observed for (A) vimentin, (B) factor VIII-related antigen, (C) CD31, (D) Prospero-related homeobox gene-1 (PROX-1). (E) Ki-67. (F) Neoplastic cells did not label for cytokeratin, (G) synaptophysin, (H) chromogranin-A. (I) Strong CD3 and (J) CD20 labeling was observed among lymphocytes forming discrete follicle-like structures at the periphery of the neoplasm. All photomicrographs are shown at x 40 magnification.
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case_images: PMC8569467_01_fvets-08-666226-g0004.jpg
case_images: F4
case_images: IHC assessment was performed to further characterize the neoplasm, as well as discriminate between blood vessel and lymphatic endothelial origin (Figure 4). IHC was performed revealing positive cytoplasmic labeling of neoplastic cells for vWf (rabbit polyclonal, 1:1,000, Dako cat.