Splenic littoral cell haemangioendothelioma: a new low-grade variant of malignant littoral cell tumour

Aims: Littoral cell angioma is a recently described splenic vascular tumour of splenic sinus lining cells. Almost all cases of splenic littoral cell tumours hitherto described were benign. Methods and results: A splenic littoral cell tumour recurred 8 years after splenectomy, with an abdominal mass and multiple liver metastases, resulting in the patient's death. Histologically, the original splenic tumour showed solid areas with small necrotic foci in addition to large areas of typical littoral cell angioma. The recurrent tumours showed increased solid architecture and slightly increased nuclear atypia. The tumours showed an immunohistochemical profile positive for factor VIII. CD31, CD68, cathepsin D, and CD21 and negative for CD34 and CD8. consistent with the immunophenotype of classic littoral cell angioma. Ki67 index in the recurrent tumours was higher than in the primary tumour. Conclusions: The mildly atypical. but not frankly malignant, histological features as well as the protracted clinical course support definition of the tumour as 'littoral cell haemangloendothelioma'. Low rate of Ki67 staining and diploid DNA histogram with low S-phase fraction of the tumours are in accordance with a low-grade malignancy, Literature review revealed two other cases of littoral cell tumours with disseminated disease that may be other examples of littoral cell haemangioendothelioma. Littoral cell haemangioendothelioma should be distinguished from the overtly malignant splenic angiosarcomas, of which a few may show splenic lining cell differentiation with some immunohistochemical features of littoral cells. Due to difficulties in predicting biological behaviour based on histological features of splenic littoral cell tumours. a long-term follow-up for these patients, especially for those with atypical histology, is recommended.