Angiomyxolipoma in the 5th Metatarsal Base Region: A Case Report

The angiomyxolipoma is a very rare clinical entity that is considered a variant form of a common lipoma or of a spindle-cell lipoma, however two distinct entities are currently controversial. We report a 56-year-old previous healthy woman who had chief complaint of slow growing mass on the right foot for 3 years. Radiologic examination, ultrasonography, excision biopsy, immunohistochemistry was evaluated. Final diagnosis of angiomyxolipoma was done. We reviewed current articles about angiomyxolipoma and compared with our result. We discussed about its clinical significance.


Case Report
We report a 56-year-old previous healthy woman who had chief complaint of slow growing mass on the right foot for 3 years. The patient had skin hyperkeratosis on the lateral side of 5th metatarsal base and had occasional pain, VAS score of 2 per examination, there was a relatively well demarcated subcutaneous mass, soft and has irregular surface, oval shape with 2 cm diameter, on the fifth metatarsal base area ( Figure 1). The patient had tenderness on mass area. The patient had no trauma history and related past history. The mass showed non-specific radiolucent soft tissue mass density on plain film. Ultrasonography was performed, and revealed an inhomogeneous, lobulated, slightly hyperechoic mass lesion. It measured 1.7 × 0.9 × 1.4 cm on diameter and partly showed slightly increased blood flow (Figure 2). The patient wanted to delay the surgical removal and we carefully followed up the patient for 14 months and there was no change of the character and the size of the mass. After 14 months of follow up, the patient underwent the surgery for excisional biopsy. The surgery was done under peripheral nerve block anaesthesia with semi-lateral recumbent position. Routine orthopaedic drape was done and esmarch tourniquet was applied. Transverse incision was done and lipogenic mass was dissected for biopsy. Skin layer by layer suture was done after vigorous irrigation with gentle compressive dressing. Intraoperative finding showed that the mass mimicked lipoma grossly. But microscopically, it showed specific myxomatous findings. Random mixture of myxoid areas, fibrotic areas, mature adipose tissue, blood vessels and minimal inflammatory invasion was observed. It showed positive staining of the CD31, CD34, Vimentin, S-100 protein (S100), smooth muscle actin (SMA), Desmin, Von willebrand factor (factor 8) and negative staining of human melanoma black 45 (HMB-45), Ki-67, alkaline lymphoma kinase (ALK), cytokeratin AE1/AE3 (CK AR1/3) in immunohistochemical analysis (Table 1).   Final diagnosis of angiomyxolipoma was achieved. Surgical wound has mild pain but clean in inspection. On 4 weeks after surgery follow up, the hyperkeratosis was exfoliated. On 6 weeks follow up, the wound was completely healed with no pain. After 1 year of follow up, there has been no recurrence (Figures 3-5).

Discussion
Angiomyxolipoma was first reported by Mai et al. and there has been 20 reported case of since then. About half of patient with angiomyxolipoma has subcutaneous lesion but various different occurrence location was also reported. 16 men and 4 women have been reported and it is suggested that male predominance exists. The patient age ranged from 4 to 70 years with irregular distribution. There is no predilection to race, ethnicity or age [9,10].
Among 20 reported patients, 12 patients had painful mass and 8 patients had painless mass. Depending on location, mass symptoms were also reported. 18 cases were single lesion and 2 cases were multiple lesion [11][12][13]. By reported literature, disease duration ranged from 3 months to 7 years and follow up duration ranged from 2 months to 8 years but no malignant change or local recurrence were reported [7][8][9].
Radiologic specific finding doesn't exist and the tumor has heterogeneous signal intensity on MR because of its heterogeneous mixture property of components [11]. Its cut surface is yellowish, mixture of fat and mucus. The tumor sometimes has focal haemorrhage with vessel ectasia. In this case, we found focal increased local blood flow on USG.
Microscopically, paucicellular myxoid tissue, mature adipose tissue, dilated and various sized congestive blood vessels were randomly mixed and mild inflammatory infiltration was observed. We did immunohistochemical stain for further differential diagnosis. The three major components of angiomyxolipoma were mature tissue and the mass has its all unique cellular property. After 1 years of follow-up, no recurrence has been observed in this case, assuming the benign nature of the lesion. But Careful follow-up was needed because one possible but important differential diagnosis is myxoidliposarcoma which is highly malignant lesion more common than angiomyxolipoma [11,12]. Other differential diagnosis contains spindle cell lipoma, angiomyolipoma, angiolipoma, angiomyofibroblastoma, superficial angiomyxoma, fibroepithelial stromal polyps, myxoidlipomatous tumors, myxoid leiomyoma which are all benign mass, differs from each other by histologic proportion of lipomatous, angiomatous, myomatous, fibrous property [12].
We suggest that clinicians should consider early biopsy when a patient has growing lipomatous lesion, because the final diagnosis can be only achieved by pathologic biopsy and immunochemistry.