Small echogenic renal masses: how often is computed tomography used to confirm the sonographic suspicion of angiomyolipoma?

Lymph nodal involvement by renal angiomyolipoma

Angiomyolipoma of the kidney is a clonal neoplasm, apparently part of a family of neoplasms derived from perivascular epithelial cells. A 40-year-old woman presented with right flank pain and an otherwise non-significant medical history. An abdominal computed tomography scan revealed an 18 cm solid mass in the mid-portion of the right kidney and multiple perihilar lymph nodes. Presumptive diagnosis was renal cell carcinoma. Right radical nephrectomy and a perihilar lymph node dissection was performed through a Chevron incision for the anticipated diagnosis of renal adenocarcinoma. The renal tumor was diagnosed as angiomyolipoma and a component was identified pathologically in a dissected lymph node. There was no evidence of tumor recurrence in the follow-up period of eight years. The consensus from other studies suggests that this phenomenon is a manifestation of the multicentric nature of angiomyolipoma, rather than due to metastasis. Genetic studies may resolve this question in the future.

Renal angiomyolipoma with epithelioid sarcomatous transformation and metastases: demonstration of the same genetic defects in the primary and metastatic lesions

Angiomyolipoma (AML) is a benign neoplasm that occurs either sporadically or in patients with tuberous sclerosis complex (TSC) and shows frequent allelic losses at chromosome arm 16p. It has been suggested recently that the melanogenesis marker-positive perivascular epithelioid cell (PEC) has been found consistently in AML. The authors report a 50-year-old woman without evidence of TSC affected by classic renal AML containing an area composed of atypical epithelioid cells with the same morphoimmunophenotypic characters of PEC. After 7 years from surgical removal of the lesion, the patient developed a local recurrence and successive lung and abdominal metastases that showed morphologic and immunohistochemical features overlapping those of the epithelioid area of the previously removed AML. Genetic analysis showed that the classic AML and its epithelioid area as well as the pulmonary and abdominal metastases shared the same allelic loss on chromosome arm 16p. Based on these findings, the authors view this case as evidence of a malignant transformation of a classic AML with morphologic, immunophenotypic, and genetic demonstration of its clonal origin.

Renal angiomyolipoma in children: diagnositc difficulty in 3 patients

PURPOSE

Because angiomyolipoma is less common in children than in adults, its diagnosis can be difficult. We present 3 cases of pediatric angiomyolipoma in which diagnostic problems resulted due to the presenting characteristics.

MATERIALS AND METHODS

We report on 3 children with unilateral renal angiomyolipoma. Computerized tomography (CT) and ultrasonography revealed 3 large renal masses, 20, 7 and 8 cm. in diameter, respectively. A correct diagnosis was not made preoperatively in any case by CT, ultrasound or fine needle biopsy. Wilms tumor was suspected in the first patient who received preoperative chemotherapy. Imaging was inconclusive in the other 2 cases.

RESULTS

All patients underwent surgical exploration and subsequent nephrectomy due to the large size of the tumor. At followup 33, 23 and 13 months postoperatively all children were well without signs of recurrence.

CONCLUSIONS

It has been reported that the demonstration of fat on renal ultrasound and CT can diagnose angiomyolipoma in 95% of the cases. Most radiologists rely solely on CT demonstration of lipid density in the renal mass to diagnose angiomyolipoma but the identification at imaging of lipid tissue may be difficult in small tumors. In our cases the fat content of the tumors was less than 10% despite the large size. This low fat content results in misdiagnosis, since fatty tissue is also present in other renal tumors, such as lipoma, liposarcoma, teratoma and Wilms tumors. We recommend conservative surgery when tumor size permits in pediatric patients with angiomyolipoma to avoid chemotherapy.