Benign vascular neoplasms of the spleen with myoid and angioendotheliomatous features

Aims: To present the clinical light microscopic and immunophenotypic featur es of a distinctive vascular neoplasm of the spleen. Methods ann results: Two of the splenic lesions arose in children, and one was found in an adult. They ranged from 19 to 40mm diameter and histologica lly were quite similar. Sheets of large epithelioid cells with a spectrum o f nuclear configurations ranging from oval and vesicular to twisted and hyp erchromatic were noted in each case. Distinct or prominent nucleoli were pr esent in many cells, and occasional cells had nuclear pseudoinclusions. In two cases, bands of basophilic, fibroblast-rich stroma with scattered chron ic inflammatory cells were present. The mitotic rate ranged from 0/10 high- power fields (HPF) to 0.5/10 HPF in these epithelioid cells. The vascular n ature of these tumours was manifested as a sieve-like array of round, eryth rocyte-filled spaces, most with attenuated and cytologically bland lining c ells, The polygonal, epithelioid cells exhibited the following phenotype: s mooth muscle actin (SMA)+, muscle specific actin (MSA)+, vimentin+, CD31-, CD34-, CD21-, CD8-, CD68-(2/3 cases), S100-, while the lining cells were CD 34+, vimentin+ and SMA-, with variable CD31 and factor Vm related antigen e xpression. Elongated SMA+, MSA+ cell processes were evident in one case, re miniscent of previously characterized myoid elements of the normal spleen. An uneventful follow-up was noted for an three patients. Conclusions: The histology and immunophenotype set these neoplasms apart fr om classic hamartomas, haemangiomas and previously characterized (haem)angi oendotheliomas of the spleen, and may represent proliferations of myoid ele ments native to the spleen.