Case 277 -- A Left Flank Mass

Contributed by Richard Whisnant, MD
Published on line in July 2001


The patient was a 44 year-old white male who presented with a chief complaint of a left flank mass which was gradually increasing in size. The mass had been present for approximately six years and caused intermittent mild pain, especially when the patient was lying on that side.


A CT scan showed a vascular soft tissue mass of the lateral abdominal musculature with extension into subcutaneous tissues. Axial CT (Fig. 01) showed a larges mass which involved several muscle groups of the left flank, extending cranio-caudally for a substantial distance. MRI with contrast (Fig. 02) confirmed the presence of a prominent vascular component. Sagittal MRI (Fig. 03) demonstrated the extent and topography of the flank involvement. The radiologic appearance was essentially unchanged from a study 2 1/2 years earlier.


An incisional biopsy was performed, which was signed out as consistent with lipoma, but with a descriptive comment regarding abnormal vasculature which was focally present. Given the benign radiographic features and slow growth, the decision was made to proceed with a marginal excision of the mass. At the time of surgery, striking vascularity of the lesion was noted, and in fact the patient was taken back to the OR from the recovery room for persistent bleed within the field. At the time of intraoperative consultation, the pathologist could not perceive a distinct mass, and so margins were felt to be difficult to assess. The patient tolerated the procedure well, and his post-operative course was uncomplicated.


The gross specimen measured 28 x 13 x 6.5 cm, and consisted of a skin ellipse, subcutaneous tissue, and abdominal wall musculature, with obvious recent biopsy cavity (Fig. 04). No distinct mass could be identified. However, in areas of both subcutaneous adipose tissue and within muscle there were grossly visible collections of tortuous vessels, ranging from 0.5 to 1.5 cm in aggregate (Fig. 05 and Fig. 06).


Microscopic sections of the areas with dilated vessels revealed thick-walled vessels with dilated vascular channels distributed around the periphery and a chronic inflammatroy infiltrate (Fig. 07, Fig. 08, and Fig. 10). Adjacent to most of these vessels, there were collections of glomeruloid capillaries proliferating (Fig. 9 and Fig. 11). On the basis of the clinical history and H&E appearance, a diagnosis was made.


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