Cellular angiolipoma: a case report and review of the literature

Abstract

Cellular angiolipoma is a rare subtype of angiolipoma, with vascular density approaching 95%. This case report describes a 55-year-old female that presented for treatment of a mass in her left breast that had been tender to slightly painful on palpation for nearly 2 years The patient underwent surgical excision of the mass, which was pathologically confirmed as a cellular angiolipoma. As of the 3-year follow-up, the patient reported no recurrence of the lesion. It is important to report this case and refresh knowledge of this and similar lesions to raise awareness of this diagnosis and treatment and improve future management of cellular angiolipoma cases.

Introduction

Angiolipomas are composed of adipose tissue and blood vessels. They usually present as multiple, painful subcutaneous nodules on the trunk or arm of young adults. Cellular angiolipoma is a rare subtype of angiolipoma, which consists of >95% blood vessel tissue. ¹ However, the lesion is sometimes highly cellular, which often leads to pathological diagnostic errors. This current case report presents a case of cellular angiolipoma of the breast and a review the literature on this rare entity.

Case report

In August 2021, a 55-year-old female presented at the Department of Breast Surgery, Mianyang Central Hospital, University of Electronic Science and Technology of China, Mianyang, China for the treatment of a mass in her left breast that had been tender to slightly painful on palpation for nearly 2 years. Physical examination revealed a soft subcutaneous lesion in the external upper quadrant of the breast. The remaining physical examination was normal. The patient had a long history of anaemia and received blood transfusions twice previously elsewhere. Laboratory tests, including infectious disease screenings, were negative or within normal limits. Mammography did not detect any mass in the breast and the subcutaneous mass was poorly visualized. An ultrasonographic examination showed a 0.7 cm × 0.7 cm × 0.4 cm defined hypoechoic nodule in the left breast (Figure 1). No other lesion was detected.

Figure 1.

Ultrasonographic findings in a 55-year-old female that presented for treatment of a mass in her left breast that had been tender to slightly painful on palpation for nearly 2 years: a 0.7 cm × 0.7 cm × 0.4 cm defined hypoechoic nodule in the left breast that had an abundant blood flow or marginal blood flow inside. The colour version of this figure is available at: http://imr.sagepub.com.

The patient underwent surgical excision of the nodule. In terms of the pathological examination, the excised mass was a greyish-yellow parenchyma lesion measuring 2 cm × 1 cm × 0.5 cm. Microscopic examination revealed that the lesion was located in the fatty tissue of the breast and was clearly demarcated from the surrounding tissue (Figure 2a). There was no involvement of the breast parenchyma in the lesion. It consisted of cellular spindle cells and collapsed blood vessels, and the cellular spindle cells were closely arranged (Figures 2b and 2c). Clusters of vessels of various sizes were visible, mostly at the lesion's periphery, with interstitial myxoid degeneration in some areas (Figure 2d). Differentiated mature adipose tissue was still visible at the lesion's margins and fibrin thrombi were abundant in the smaller capillaries (Figures 2e and 2f). The tumour cells were not significantly heterogeneous and rarely mitotic. According to immunohistochemistry, the tumour cells expressed smooth muscle actin, cluster of differentiation (CD)34, CD31, vimentin and epidermal growth factor, but were negative for podoplanin, human herpesvirus-8 (HHV8) and phosphorylated cytokeratin.

Figure 2.

Immunohistochemistry of the cellular angiolipoma surgically removed from a 55-year-old female that presented for treatment of a mass in her left breast that had been tender to slightly painful on palpation for nearly 2 years: (a) the lesion was located in the mammary adipose tissue and was well defined from the surrounding tissue (scale bar 500 µm); (b, c) spindle cells (blue arrow) and pressure-closing blood vessels (red arrow) can be seen under the microscope. The spindle cells were closely arranged, with interstitial myxoid degeneration (black arrow) (scale bar 200 µm); (d) clusters (red arrow) of different sizes seen at medium to high magnification (scale bar 100 µm); (e) under medium and high magnification, differentiated and mature adipocytes (blue arrow) were visible (scale bar 100 µm) and (f) no obvious atypia of the tumour cells was observed under the high magnification. Abundant microthrombi (fibrin thrombosis, black arrow) could be seen in the tumour (scale bar 100 µm). The colour version of this figure is available at: http://imr.sagepub.com.

The patient was discharged from the hospital on the second post-surgery day and was fully recovered 1 week later. As of the 3-year follow-up, the patient reported no recurrence of the lesion. The reporting of this study conforms to CARE guidelines. ² Ethics committee approval was not required for this case report. The case report did get board approval for publication. The patient’s personal details have been de-identified. Prior to the study, patient consent for treatment was obtained.

Discussion

Angiolipoma is the most common subtype of lipoma, which is a benign and slow-growing mesenchymal neoplasm. ³ It typically occurs as multiple painful subcutaneous nodules, the cause of which is unknown but may be related to the capillary network or fibrin thrombi. Histopathologically, angiolipoma is distinguished by mature adipose tissue and variable amounts of blood vessels, some of which contain fibrin thrombi.^4,5 Cellular angiolipoma is a rare subtype of angiolipoma, with vascular density approaching 95%. ¹ Its clinical feature is similar to conventional angiolipoma. Cellular angiolipoma is harder in texture and varies in colour from reddish-brown to tan, depending on the number of blood vessels present, in contrast to the regular yellow colour of a conventional angiolipoma. ⁶ Since the first formal report of three cases of cellular angiolipoma in 1990, ⁷ a thorough search of the literature in English revealed three reports of cellular angiolipoma that occurred in the subcutaneous tissue of the breast,^6,8,9 with the most recent being reported in 2013. ⁶ The neoplasm is not widely recognized and is easily misdiagnosed.

Radiographically, cellular angiolipoma presents as an irregular dense mass without unique pathological or radiological features. When cellular angiolipoma is located in the breast tissue, as parenchymal tumours, it is usually visualized by mammography and is not visible by ultrasound. ¹⁰ However, this current case occurred in the subcutaneous tissue of the breast and it was visualized by ultrasound but not identified by mammography. Because of the lack of radiological correlates, biopsies are frequently used for clinical diagnosis.

Histologically, at low magnification, the mature adipose tissue and dense cellular areas at the edge are formed without mammary lobular structure. ¹¹ It is speculated that its occurrence arises from within the subcutaneous tissue of the mammary area, not within the true mammary parenchyma. ¹⁰ Cellular angiolipoma is primarily composed of blood vessels and spindle cells with only a few areas of adipose tissue. ⁹ More than 95% of the neoplasm tissues is made up of blood vessels and <5% of the neoplasm is made up of adipocytic components. ¹ Furthermore, blood vessels in angiolipomas are mostly capillaries, whereas in cellular angiolipoma, moderately large venous vessels and intravascular fibrinous thrombi are often found, as well as a variable number of interstitial spindle cells, and a myxoid stroma has also been found between capillaries. ¹⁰

This current case was a cellular angiolipoma, because it was rich in blood vessels and occurred in the mammary gland, but attention was paid to distinguish it from other lipomas and vascular tumours, including Kaposi’s sarcoma (KS), spindle cell lipoma (SCL), spindle cell haemangioma and capillary haemangioma of infancy. The following key differential diagnostic features should be noted for this current case: (i) the tumour boundary was clear and capsular in some areas; (ii) the blood vessels were extremely abundant, endothelial cells were typical, with significant microthrombus, and there was a small fat component; (iii) the immunohistochemistry indicated that it was HHV8 negative; (iv) the supplementary medical history revealed that the patient’s disease had been present for many years and a clinical examination showed that the mass boundary was clear.

Kaposi’s sarcoma is a low-grade vascular tumour associated with HHV8 infection that typically manifests as multiple skin nodules, but it can also involve the mucosa and viscera.^12,13 KS histopathology is distinguished by the proliferation of both spindle cells and vessels. These features are similar to those of cellular angiolipoma. Eosinophilic cells, extravasated red blood cells and haemosiderin-laden macrophages are also common in KS lesions. Typical KS lesions, on the other hand, lack considerable cellular pleomorphism, necrosis and a high number of mitotic figures. These early histological changes may be subtle and thus easily missed during a biopsy. CD31, CD34 and HHV8 stains are detectable in KS cells using immunohistochemistry.^13,14

Spindle cell lipoma is a benign lipomatous lump that typically manifests as a solitary, painless subcutaneous nodule in the neck and back of older males. The histological features of SCL are composed of mature adipose tissue and fibroblast-like spindle cells, wiry bundles of collagen are observed between the spindle cell fibrils and the interstitium can be myxoid, with no evidence of small-calibre vessels. ¹⁵ SCL has been found to express CD34 and B-cell lymphoma 2, but not S-100. ¹⁶

Spindle cell haemangioma is a primary benign vascular neoplasm that consists of cavernous haemangioma-like regions, with cavernous vascular cavity spaces. Sometimes mechanical thrombus can be seen inside. ¹⁷ It is reported that thick or thin-walled vessels can be found at the periphery of the lesion. Spindle-shaped or round stromal cells may be found in the cavernous space, some of which are vacuolated, which is probably not observed in cellular angiolipoma. ¹⁸

Capillary haemangioma of infancy is an immature capillary haemangioma that typically occurs on the head or neck of infants. Histological morphology varies with disease course. The early lesions consist of fat spindle-shaped endothelial cells with inconspicuous vascular spaces surrounding the lumen, moderate amounts of nuclear division and mast cells and factor Xla-positive stromal cells. However, as the lesions mature, the endothelial cells become flattened, resembling adult-type capillary hemangiomas. ¹⁹

In conclusion, cellular angiolipoma is a benign mesenchymal neoplasm that grows slowly, has no reported potential for malignant transformation, and it can be cured by excision. Cellular angiolipoma differs from conventional lipomas in that it mostly lacks an intact envelope and is poorly demarcated from the surrounding tissue. Therefore, identifying the extent of the lesion while excising the neoplasm as completely as possible is important to minimize damage and postoperative scarring. Because most cellular angiolipomas contain a large number of blood vessels, they must be carefully separated and firmly ligated during surgery. This current case has been reported to refresh the knowledge of this and similar lesions in order to raise awareness of this diagnosis and treatment, and improve the future management of cellular angiolipoma cases.

Supplemental Material

sj-pdf-1-imr-10.1177_03000605231206290 - Supplemental material for Cellular angiolipoma: a case report and review of the literature

Supplemental material, sj-pdf-1-imr-10.1177_03000605231206290 for Cellular angiolipoma: a case report and review of the literature by Zhen Zhang, Li-Jun Peng and Yu-Jun Tong in Journal of International Medical Research