Clinical diagnosis
Case 77
【Progress】Her concern was whether her splenic tumor is malignant or not. We explained radiologic findings about splenic tumors, merit and risk of splenic biopsy or splenectomy, and the threatening of its size increasing and the possible rupture. She made a choice of watching observation. She mentioned that in case of tumor increase, she would take splenectomy. She did not agree to take histological examination.
【Discussion】
Splenic hamartoma is a relatively rare tumor with an incidence of 0.12% of autopsied cases (1, 2, 3). There were 113 reported cases in Japan at time of 2008 (4). It can occur at any age (14.3% of the reported cases: pediatric children) with no gender difference (5). It usually causes no special symptom but can occur abdominal pain and hypersplenism accompanied with tumor size growing. Because splenic rupture can occur, the periodic follow-up is crucial, although splenic hamartoma is categorized in benign tumor.
Splenic hamartoma results from congenital growth disorder and is a composed of an anomalous mixture of splenic elements, such as red pulp, white pulp, fibrous tissue, fat tissue and calcification (1-3). Splenic hamartoma is histologically classified as red pulp type, white pulp type and fibrous type (2, 3) and radiologically classified into fibrous type and non-fibrous type (6, 7). In hamartoma including dominant fibrous tissue, MRI showed hypo- or iso-intensity on T1WI and hypo-intensity on T2WI. Meanwhile, in non-fibrous hamartoma, MRI showed iso-intensity on T1WI and hyper-intensity on T2WI. Both types demonstrated heterogeneous enhancement on the arterial phase and uniformly homogeneous enhancement on the delayed phase. Enhancement pattern of hamartoma mimics that of hemangioma. Especially, non-fibrous type hamartoma should differentiate from hemangioma (6, 7). Non-fibrous hamartoma appears iso-intensity on T1WI and heterogeneous hyperintensity (or hypointensity) on T2WI, while hemangioma appears low-intensity on T1WI and homogeneous hyperintensity on T2WI.
Our splenic tumor appeared iso-intensity on T1WI and hypo-intensity associated with iso-intensity like septum (heterogeneous intensity) on T2WI, and iso-density on non-enhanced CT and almost homogeneous delayed enhancement on delayed phase of enhanced CT. It is considered that our splenic tumor has characteristic images of fibrous type hamartoma.
Although splenic mass are not so common, as malignant splenic tumors, malignant lymphoma, angiosarcoma, metastatic tumors are listed and as benign ones, hemangioma, lymphangioma, hamartoma, granuloma, abscess and peliosis are listed. They have their own specific image characteristics (8).
In short, malignant lymphoma appears hypo-vascular tumor and high signal intensity on Diffusion weighted image (DWI) of MRI. Angiosarcoma appears as aggressive growing and hypervascular tumor and high signal intensity on DWI. Meanwhile, benign tumors do not appear high signal intensity on DWI. Splenic hemangiomas are hypointensity on T1WI and homogeneous hyperintensity on T2WI. Following enhancement, gradual central fill-in and persistent retention of contrast agent on the delayed phase. Lymphangioma is hypovascular cystic lesions. Peliosis of the spleen is caused by sinusoidal dilatation and appears cyst-like blood-filled cyst like a complicated cyst. In our case, DWI showed hypo-signal intensity, indicating benign tumor and different image pattern from other benign tumors.
【Summary】
We present a forty two-year-old female with splenic hamartoma whose image showed the homogeneous stain lesion as splenic parenchyma on delayed phase of enhanced CT and heterogeneous low signal intensity on T2WI of MRI plus no high signal intensity on DWI, indicating benign tumor with fibrous component. We should keep in mind that the characteristic image of splenic hamartoma is low signal intensity on T2WI which is different from splenic hemangioma.
【References】
1.Lam KY, et al. . Splenic vascular lesions: unusual features and a review of the literature. Aust N Z J Surg. 1999;69:422–425.
2.Silverman ML, LiVolsi VA. Splenic hamartoma. Am J Clin Pathol. 1978;70:224–9. [PubMed]
3.Lee H, Maeda K. Hamartoma of the spleen. Arch. Pathol. Lab. Med. 2009;133 (1): 147-51. doi:10.1043/1543-2165-133.1.147 - Pubmed citation
4.Yokoi, S et al. A case of splenic hamartoma associated with threatened rupture. Endoscopic Surgery (EAES) . Surg Endosc 2008;22:821―848
5.Hayes TC, et al. Symptomatic splenic hamartoma: case report and literature review. Pediatrics. 1998;101:E10. [PubMed]
6.Abbott RM, et al. From the archives of the AFIP: primary vascular neoplasms of the spleen: radiologic-pathologic correlation. Radiographics. 2004;24 (4): 1137-63.
7.Yu, RS, et al. Imaging findings of splenic hamartoma. World J Gastroenterol. 2004 Sep 1; 10(17): 2613–2615.
8.Kaza, RK, et al. Primary and secondary neoplasms of the spleen. Cancer Imaging. 2010; 10(1): 173–182. Published online 2010 Aug 13. doi:10.1102/1470-7330.2010.0026PMCID: PMC2943678
2017.10.25