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9 June 2010 - Case #181

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Thanks to Dr. Juan Jos Segura Fonseca, Laboratorio de Patologa Diagnstica, S.A., San Jos, Costa Rica, for contributing this case and much of the discussion. This case was reviewed in May 2020 by Dr. Jennifer Bennett, University of Chicago and Dr. Carlos Parra-Herran, University of Toronto.


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Case #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 nonencapsulated 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:



Microscopic images:




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Diagnosis: Aggressive angiomyxoma of the vulva

Immunohistochemistry images:

Desmin

Progesterone



Discussion:
Many small and medium sized vessels in a myxomatous stroma were present (figures 3 and 4). The stromal cells resembled spindle shaped fibroblasts (figure 5). There was prominent condensation of collagen around vessels, with spinning off of muscle fibers (figures 6 and 7). Small hemorrhages were present around small capillaries (figure 8). The spindle cells were strongly positive for desmin (figure 9) and progesterone receptor (figure 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 as a slow growing, low grade neoplasm involving the pelvis and vulvoperineal region, with a high risk for local recurrence, which may occur after many years (Am J Surg Pathol 1983;7:463). In their original report of 9 cases, 6 were located in the vulva. Of 29 cases reported by Fetsch et al, 10 were vulvoperineal tumors (Cancer 1996;78:79). 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 2 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 dependent, 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:
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).


Image 01 Image 02