9 June 2010 – Case of the Week #181

 

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Case of the Week #181

 

Clinical History

 

A 28 year old woman was seen in the outpatient clinic because of a 4 month history of progressive enlargement and swelling of the right labium major, with obvious asymmetry.

 

During surgery, a non encapsulated tumor was found, which infiltrated down to the pelvic floor, making a complete resection difficult. The tumor was 9 x 6 x 5 cm with a white, gelatinous consistency.

 

Gross images
   

 

Micro images:

       

 

       

 

Immunohistochemistry images:

   

Desmin                       Progesterone

 

What is your diagnosis?

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Diagnosis:

 

Aggressive angiomyxoma of the vulva

 

Discussion:

 

Many small and medium sized vessels in a myxomatous stroma were present (Fig. 3 and 4). The stromal cells resembled spindle shaped fibroblasts (Fig. 5). There was prominent condensation of collagen around vessels, with spinning off of muscle fibers (Figs. 6 and 7). Small hemorrhages were present around small capillaries (Fig. 8). The spindle cells were strongly positive for desmin (Fig. 9) and progesterone receptor (Fig.10).

 

Aggressive angiomyxoma is a rare, distinctive, infiltrative mesenchymal tumor usually found in women of reproductive age, frequently in their third decade of life.  It was first described by Steeper and Rosai (Am J Surg Pathol 1983;7:463) as a slow growing, low grade neoplasm involving the pelvis and vulvo-perineal region, with a high risk for local recurrence, which may occur after many years. In their original report of nine cases, six were located in the vulva. Of twenty nine cases reported by Fetsch et al (Cancer 1996;78:79), ten were vulvo-perineal tumors. Although the tumor is locally aggressive with a propensity to infiltrate deep soft tissue in a diffuse manner, the metastatic potential is very low. Only two cases with metastasis have been reported (N Engl J Med 1999;341:1772, Hum Pathol 2003;34:1072).

 

Grossly, the tumor is rubbery, white and gelatinous. Most tumors are 6 to 9 cm, but they are rarely huge and pedunculated (Kaohsiung J Med Sci 2006;22:301, Indian J Pathol Microbiol 2008;51:259). Histologically, there is a myxomatous stroma and a hypocellular pattern of mesenchymal stellate and spindle shaped cells with a myofibroblastic morphology, without nuclear atypia or mitoses. Numerous small capillaries, venules, veins and medium size arterioles are present. In some vessels, there is a peculiar perivascular eosinophilic condensation of collagen. Short bundles of smooth muscle fibers seem to spin off from the arterial walls into the stroma. Small hemorrhages around capillaries with fibrin thrombi are present. There are also entrapped nerves and adipocytes.

 

The stromal cells are strongly immunoreactive for desmin, and are also positive for vimentin and actin. The tumor appears to be hormone dependant, based on immunostaining for estrogen and progesterone receptors (J Clin Pathol 2000;53:603).  Tumor cells are variably positive for smooth muscle actin, and negative for S100 (Int J Gynecol Cancer 2005;15:140).

 

The differential diagnosis includes other vulvar myxoid tumors:

- Plexiform neurofibroma: neural morphology, S100+
- Angiomyofibroblastoma: hypo- and hypercellular with perivascular multinucleated giant cells

- Myxoid smooth muscle tumors

- Superficial angyomyxoma: tumor of superficial dermis

- Vulvar hypertrophy with lymphedema: bilateral, similar histologically but with prominent ectatic tortuous lymphatic vessels and no thick walled vessels (Arch Pathol Lab Med 2000;124:1697)

 

Treatment is surgical excision, although the tumors are difficult to completely excise and there is a high recurrence rate.  GnRH agonist therapy has also been used with success (Gynecol Oncol 2006;100:623).

 

Additional references: PathologyOutlines.com-Vulva chapter

 

Nat Pernick, M.D., President,

and Kara Hamilton, M.S., Associate Medical Editor

PathologyOutlines.com, Inc.

30100 Telegraph Road, Suite 408

Bingham Farms, Michigan (USA) 48025

Telephone: 248/646-0325

Email: NatPernick@Hotmail.com

Alternate email: NatPernick@gmail.com