Macroscopically, the tumour was apparently well capsulated, multi-lobated with a greyish cut surface and hemorrhagic alternated to sclerotic areas. Microscopically, a thin fibrous capsule incompletely delimitated the tumour mass which was focally infiltrated the liver parenchyma (Figure 2A). The tumour was mainly characterized by “staghorn-like” vascular branching spaces surrounded by spindle or epithelioid cells sometimes with abundant clear cytoplasm embedded in a rich myxoid stroma (Figure 2BD). Alternating, sclerotic areas and “solid growth” were characterized by small vessels with fascicular arrangements of neoplastic cells (Figure 2E-F). A multilayered concentric proliferation of spindle cells with myoid features around blood vessels was also observed (Figure 2G-H). Atypia and mitosis were absent. Small areas of coagulative necrosis were detected probably due to the previously performed fine needle aspiration biopsy.
Immunohistochemical examination revealed that tumour cells were α-smooth muscle actin positive (Figure 3A) whereas CD34 (Figure 3B), CD31 (except for endothelial cells covering the vascular spaces), CD99 and bcl-2 immonodetection were negative. The proliferative index evaluated by Ki-67 nuclear positivity was lower than 1% (Figure 3C). Concentric proliferations of spindle cells around vessels were α-smooth muscle actin positive (Figure 3D). A diagnosis of myopericytoma was made. After 24 months, the patient is alive with no recurrence.
Although generally benign, pericytic tumours can recur following excision. Recurrence is usually related to poor circumscription of a lesion and so incomplete surgical removal. Moreover, true malignant cases of perivascular tumour with distant metastasis have been rarely described[9].
Nevertheless, the histological aspect is not always predictive of the clinical behaviour of some tumours, especially those exhibiting “glomus-type” features[9]. High mitotic activity (typical and atypical), the large tumour size and visceral location are diagnostic criteria of malignancy[1,9]. When a tumour does not fulfill all these criteria, the designation “uncertain malignant potential” seems to be appropriate, suggesting a possible more aggressive biological behavior. The presence of a prominent vascularization suggests a potential target for additional post-surgical therapy of more aggressive cases[10,11].
In conclusion, it is important to take the possibility of a pericytic tumour into consideration for a correct differential diagnosis of primary liver neoplasms for a better management of patient care.
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