21 September 2016 - Case of the Week #401

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Case of the Week #401

Clinical history:
A five week old, full term boy presented with respiratory distress, URI symptoms and thrombocytopenia. Chest CT showed pericardial effusion, cardiac tamponade and a supracardiac soft tissue mass, 2.9 x 2.4 x 1.1 cm. He had a mediastinoscopy with excisional biopsy.


Micro images:

Low power view

20x




What is your diagnosis?































Diagnosis:
Kaposiform hemangioendothelioma


Discussion:

Special stains:

CD31 (20x)

CD34

SMA

Vimentin



Microscopic examination shows a cellular tumor composed of bland spindle cells in a fascicular arrangement with vasoformative slit-like lumina and extravasated red blood cells ("kaposiform" morphology). The tumor cells were positive for CD31, CD34, SMA and vimentin, and negative for desmin, myogenin, CK AE1/3, EMA, S100, synaptophysin and HHV8 (stains not shown). Ki67 was positive in ~15% of the tumor cells.

Kaposiform hemangioendothelioma (KHE) is a rare, locally aggressive, immature vascular neoplasm of children. The usual presentation is a violaceous skin lesion, but it may also present viscerally, typically in the retroperitoneum or mediastinum (Arch Pathol Lab Med 2004;128:678). KHE may be associated with Kasabach-Merritt syndrome, in which platelet trapping and hemorrhage occur within the tumor, leading to a potentially life threatening thrombocytopenic coagulopathy. First described in 1940, 200 cases have now been reported (J Indian Assoc Pediatr Surg 2012;17:33), typically within large visceral lesions (Arch Pathol Lab Med 2004;128:678).

Treatment of KHE consists of vincristine and anti-platelet aggregant therapy. Prognosis is excellent if thrombocytopenia is controlled (Pediatr Blood Cancer 2013;60:1478). Multiple investigators have described successful pharmacological management with vincristine, ticlopidine and aspirin (Pediatr Hematol Oncol 2010;27:641). Recently, VEGF inhibitors and mTOR pathway inhibitors such as Sirolimus have been shown to be effective (Br J Haematol 2015;171:38). This patient was treated with vincristine and is doing well.


Discussion edited by: Dr. Hillary Z. Kimbrell, Myriad Genetics, Inc., Utah (USA)