Sinusoidal hemangioma is a distinctive subset of a group of cavernous hemangioma first described by Calonje and Fletcher1 in 1991. Clinically, it develops in middle-aged adults, predominantly in females, and presents as a solitary, painless, bluish subcutaneous nodule. Although anatomic distribution is wide, the tumor presents most frequently on the extremities, trunk, and often on the breast and scalp1. Histologically, it is characterized by a well-circumscribed lobulated architecture composed of dilated interconnecting, thin-walled vascular channels that frequently show a pseudopapillary pattern and a back-to-back arrangement with scanty intervening stroma1-3.

Lipoma is a common benign soft tissue tumor, that usually develops between the ages of 40 and 70 years. Histologically, lipomas contain mature adipocytes as a principle component. They tend to be surrounded by a thin capsule of connective tissue and are composed often entirely of normal fat cells indistinguishable from fat cells in the subcutaneous tissue4.

Sinusoidal hemangioma is rarely reported. Here, we report on an interesting case of sinusoidal hemangioma with a lipoma on the right arm that occurred in a 43-year old male patient. To the best of our knowledge, this is the first report of a case with the combined tumors.

A 43-year-old male visited our clinic complaining of an asymptomatic solitary subcutaneous nodule on his right upper arm. He presented with a two-month history and claimed that he had noticed it by accident. On physical examination there were no symptoms except for a skin lesion. Skin examination revealed a solitary, relatively well-defined, pea-sized bluish subcutaneous nodule on the right upper arm (Fig. 1). There was tenderness on palpation, and no bleeding or ulceration was observed. All laboratory examinations, including a complete blood count, blood coagulation test, routine chemistry, and venereal disease research laboratory test were either in the normal range or negative. Histopathologically, there was a well-circumscribed, lobulated subcutaneous mass. The mass was not encapsulated, and was composed of dilated and interconnecting, thin-walled vascular channels forming a sinusoidal structure. The channels were filled with many red blood cells. On the right side of the mass, was a well-circumscribed collection of benign mature adipocytes (Fig. 2). The dilated vessels showed a pseudopapillary pattern and a back-to-back arrangement with scanty intervening stroma. The nuclei of the endothelial cells showed focal hyperchromasia and mild pleomorphism, but no mitotic figures (Fig. 3). In addition, the mature adipocytes were surrounded by a capsule of thin connective tissue. However, features of inflammation and malignancy were not seen (Fig. 4). Based on the clinical and histological findings, the patient was diagnosed with sinusoidal hemangioma associated with lipoma, after which a simple excision was performed. Follow-up for 1 month after excision revealed no tendency to either local recurrence or metastasis.

Sinus hemangioma is a relatively rare variant of cavernous hemangioma. A typical feature during histopathology is the presence of gaping, markedly dilated and congested, thin-walled, back-to-back vascular spaces in a sieve-like or sinusoidal arrangement. Pseudopapillary structures due to cross-sectioning of these spaces focally resemble intravascular papillary endothelial hyperplasia. The blood vessels are lined by bland, flat endothelial cells, which can be focally prominent and mildly pleomorphic. Thrombosis, hyalinization, dystrophic calcification, and even areas of infarction can be seen in older lesions1-3. Since they are composed of dilated vessels in subcutaneous tissue, cavernous hemangiomas are considered in the differential diagnosis. Cavernous hemangioma differs principally in its tendency to appear in childhood, be of a larger size, and present on the upper body. Histologically, in contrast to sinusoidal hemangioma, a cavernous lesion has a nonlobular, poorly demarcated structure and no pseudopapillary appearance3. Although the anatomical distribution of sinusoidal hemangioma is wide, tumors often present in the breast. In our case, cytological atypia and hyperchromasia were seen histologically in the endothelial and perivascular cells. Therefore, the need to differentiate this type of tumor from well-differentiated angiosarcoma and avoid unnecessary radical treatment was emphasized1,3. Angiosarcoma is an interstitial lesion and not a subcutaneous lesion. It typically shows diffuse infiltration, atypical mitosis and multilayered endothelial cells3. Another tumor that shows papillary projection is the intravascular papillary endothelial hyperplasia. This tumor contains eosinophilic interstitial stroma, which are not observed in sinusoidal hemangioma.

Another subcutaneous hemangioma, like subcutaneous pyogenic granuloma (lobular capillary hemangioma), spindle cell hemangioma and cellular angiolipoma are considered to be part of the differential diagnosis. The characteristic histopathologic features of subcutaneous pyogenic granuloma are distinctive lobules of dilated and congested capillaries. The angiomatous tissue is surrounded by myxoid stroma containing scattered spindle- and stellate-shaped connective tissue cells and occasional mast cells5. The lesion of spindle cell hemangioma is characterized by cavernous or slit-like vascular proliferations lined with a thin layer of endothelium, alternating with cellular areas consisting predominantly of spindle cells6. The histopathological findings of cellular angiolipoma show well-circumscribed tumors composed of vascular endothelial and spindle cells forming vascular spaces intermingled with scattered adipocytes4,7. Thus, it is possible to distinguish between these subcutaneous hemangiomas and sinusoidal hemangiomas.

Sinusoidal hemangioma combined with another benign tumor has never been reported. However Calonje and Fletcher1 reported a case of sinusoidal hemangioma with metaplastic ossification while Nakamura and Miyachi2 reported one that showed calcification and organized thrombi.

Lipoma is the most common benign mesenchymal neoplasm composed of mature adipocytes, and usually presents between the ages of 40 and 70 years. Most lipomas occur in subcutaneous tissue as superficial lipomas, and rarely in interosseous tissue as deep lipomas. Subcutaneous lipomas are frequently located on the trunk, and occasionally occur on the neck, forearm, and axilla. Histologically, they tend to be surrounded by a capsule of thin connective tissue and are composed often entirely of normal fat cells that are indistinguishable from fat cells in the subcutaneous tissue4.

Two-months earlier, our patient had accidentally noticed a subcutaneous nodule on the right upper arm. Clinically it was suspected to be a lipoma, but was diagnosed histologically as a sinusoidal hemangioma combined with lipoma.

The pathophysiology of a sinusoidal hemangioma combined with lipoma has not been reported. Several recent electron microscopic studies suggest that adipocytes are closely related to capillaries and originate from perivascular cells, like prenatal adipogenesis8. From these studies, we believe that adipocytes from the perivascular cells, which make the sinusoidal hemangioma, also formed the lipoma. Also, as mentioned earlier, in the case of sinusoidal hemangioma with ossification, metaplastic lipoma can not be ruled out. Alternatively, the lipoma may have occurred accidentally from the abnormal condensation of adipocytes combined with the sinusoidal hemangioma.

Vascular endothelial growth factor (VEGF) and basic fibroblast growth factor (bFGF) have been demonstrated as regulators of angiogenesis9. These factors are found in higher concentrations and play a role in proliferative hemangiomas. Since adipose tissue serves as an important conduit for the vasculature, it is conceivable that the angiogenic properties of this tissue may modulate the growth of the vasculature in a paracrine manner. The angiogenic cytokines (FGF-2, VEGF) released by adipocytes and endogenous cytokines such as FGF-2 play a role in the vasoproliferative response10.

The lipoma observed in our patient was able to stimulate angiogenesis. Previous cytogenetic studies showed that a substantial subset of adipose tissue tumors display a rearrangement or loss of chromosome 1311. Tharapel et al.12 suggested that the hemangioma is a common features in distal trisomy 13. Maybe the rearrangement of chromosome 13 affected our patient. However, interconnections between the sinusoidal hemangioma and lipoma could not be specifically identified, and they may be a coincidence or another type of hemangioma. Further studies will be required to investigate possible interconnections.