RESUMEN
Symplastic haemangioma is a rare vascular tumor presented with regressive and degenerative atypia in stromal cells. Its morphology represents a challenge in classification of vascular tumors, regarding their biological behaviour in particular. We present a case report of a 47-years-old female with a history of left-sided breast adenocarcinoma treated by resection followed by adjuvant chemotherapy and radiotherapy. Three years after the primary diagnosis a tumorous mass appeared in the region of upper margin of left scapula, in subcutaneous tissues and the trapezius muscle. Histologically, the tumor was formed by multiple blood vessels of varied diameter and wall thickness. Endothelial lining was bland, without atypia; thromboses were observed in vascular spaces. In the interstitium, a population of spindle and pleomorphic cells with distinctive atypia and bizarre nuclei was found. These cells showed positivity in immunohistochemical expression of smooth muscle actin, further extensive immunohistochemistry including cytokeratines was negative. Mitoses were absent, proliferating activity was minimal. Signs of infiltrative growth pattern were not found and the tumor lacked hallmarks of malignant behaviour. A diagnosis of symplastic haemangioma was established. Above mentioned atypical stromal cells show myofibroblastic and sporadically smooth muscle differentiation. Their atypical appearence is associated with degenerative alterations similar to changes in leiomyomas with bizarre nuclei or ancient schwannomas. Etiopathogenesis of these changes is not clear, there are hypotheses considering long-lasting persistence of the lesion, regression of ischaemic or postinflammatory origin, or, like in our case, postirradiative degeneration. Differential diagnosis of symplastic haemangioma is widespred and contains many histological entities of variant histogenesis and biological potential. For proper classification, an extensive investigation including immunohistochemistry, clinical and anamnestic data and imaging methods is necessary.