Superficial Myofibroblastoma in the Vulva Mimicking Aggressive Angiomyxoma: A Case Report and Review of the Literature

Abstract

Background: Superficial myofibroblastoma (SMF) is a very rare benign mesenchymal tumor in the female lower genital tract. Only 46 cases have been reported in the English language literature, among which only 7 cases arose in the vulva. Sometimes SMF histologically mimics aggressive angiomyxoma (AA) in which massive myxoid change in stroma is characteristic. We herein report a case of vulvar SMF with prominent myxoid stroma and review the literature with the emphasis on the differential diagnosis of SMF and AA.

Case presentation: a 37-year-old woman presented with a painless mass in the vulva. Magnetic resonance imaging (MRI) showed a well-circumscribed 7 cm mass in the subcutis of the vulva. The tumor was resected. Histopathologically, the tumor was characterized by sparsely populated spindle-shaped cells in the fibromyxoid stroma. Thin-walled blood vessels were detected. Mitoses or pleomorphism was not found. Tumor cells were positive for vimentin, ER, PgR, and desmin. Some cells were positive for alpha-SMA and CD34. All cells were negative for S100 protein.

Conclusions: because SMF and AA show different clinical prognoses, distinguishing SMF from AA is important. However, SMF may share many common histological features with AA: superficial localization (above fascia), sharp borderline from adjacent tissue, expansive growth pattern; a specific vascular pattern will lead to an accurate diagnosis of SMF. Familiarization with the histological characteristics of the two entities will help to make a prognostic prediction.

Figure 1

Magnetic resonance imaging of the pelvis showed a well-circumscribed mass in the vulvar subcutaneous region.

Figure 2

On histopathological examination (×10;HE), the tumor was located in the subcutaneous region. There is an uninvolved segment between the tumor and overlying squamous epithelium. The boundary between the tumor and adjacent tissue was well demarcated.

Figure 3

Tumor cells were short and spindle-shaped, arranged in no overt architecture. The nuclei were oval, without prominent atypia. The intervening matrix was edematous and myxoid ((a); ×400;HE). In some regions, fine collagen as well as dense collagen was detected ((b); ×100;HE). The vast majority of blood vessels were small and thin-walled ((c); ×100;HE). Some medium-sized blood vessels were also identified within the lesion ((d); ×100;HE). There was no specific distribution pattern of the vascularity.

Figure 4

Immunohistochemically, positive nuclear staining for ER (a) and PgR(b) was observed. Tumor cells showed cytoplastic positivity for desmin (c) and αSMA (d). CD34 (e) and S100 protein were negative in all cells(f).