Angiomyofibroblastoma of Vulva: Case Report with Histomorphological Differential Diagnosis and Review of Literature

ABSTRACT


Introduction
Angiomyofibroblastoma (AMF) is a rare, benign, non-recurrent mesenchymal neoplasm occurring mainly in the pelvi-perineal region of reproductive age females (1).They are composed of two major components, namely prominent blood vessels and stromal cells (2).In the literature, there is one case of AMF recurrence (3), and one case with sarcomatous transformation (4).Preoperative diagnosis of AMF and distinction from other soft tissue tumors is often difficult, as there are no characteristic imaging findings.It is often mistaken for a Bartholin's cyst, causing delays in diagnosis and treatment (1, 5).AMF needs to be differentiated from other mesenchymal tumors of the vulva (2, 6); more importantly from aggressive angiomyxoma (AAM) because of differences in their biological behavior (2).Local excision of the tumor mass is an adequate treatment for AMF.This report presents a case of AMF of the labia in a 40-year-old female.We have laid special emphasis on the differential diagnosis and review of literature.

Case Report
A 40-year-old married female presented in the obstetrics and gynecology clinic with menorrhagia and a slow-growing, painless mass in her left vulva, which gradually increased in size over a period of four months.She complained of dyspareunia.No other significant past, family, obstetric or gynecologic history was identified.She denied history of sexually transmitted disease, changes in appetite, bowel movements, dysuria, hematuria, fevers, chills, night sweats or weight loss.Laboratory investigations were within normal limits.On local examination, a 6×2 cm painless, cystic mass was identified in the left labia majora and was clinically diagnosed as a Bartholin's cyst.Ultrasonography (local part) showed a 6.5×2.4 cm well-defined heterogeneously isohypoechoic lesion with multiple dense echoes.Magnetic resonance imaging was subsequently performed for further characterization which revealed a 5.9×3×1.7 cm well-defined, heterogeneous altered signal intensity lesion involving the left labia majora; hypointense on T1W and hyperintense on T2W and STIR images.Possible radiological differentials included an infected hydrocele of the canal of Nuck, Bartholin's cyst and epidermoid vulval cyst.Complete excision of the cystic swelling was performed with clear margins.
The specimen was a 5.5×3.5×2cm single, nodular, pseudo-encapsulated mass with a pale-pink, soft, solid, homogenous and fleshy cut surface (Fig 1 a).There was no evidence of cystic areas, necrosis or hemorrhage.Microscopic examination revealed a tumor with alternating hypercellular and hypocellular areas, comprising spindle cells with bland, hyperchromatic nuclei, indistinct nucleoli and eosinophilic cytoplasm that appeared to be clustered around numerous capillary-sized thin-walled blood vessels.The stroma was loose, edematous and collagenous (Fig. 1 b-d) and showed the presence of scattered chronic inflammatory infiltrate.Occasional intralesional adipose tissue was seen.However, there was no evidence of mitosis, necrosis, perivascular hyalinization, atypia or malignancy in the sections studied and a diagnosis of AMF was given.No evidence of recurrence was seen in the three months since excision.

Discussion
AMF is a rare, benign, non-recurring mesenchymal tumor composed of myofibroblasts and blood vessels.It was first recognized by Fletcher et al., in the early 1990s (5).It occurs almost exclusively in the subcutaneous tissue of the vulvo-vaginal region of women but can also occur occasionally in the ischiorectal fossa, cervix, and bladder, as well as similar tumors have been reported in the spermatic cord, scrotum, and perineum of men (7).It is thought to be derived from the subepithelial mesenchyme of the lower genital tract (1).
It presents as a well-circumscribed, 2 to 8 cm, painless mass.The cut surface is usually soft, tan-white and solid.Histologically, it is a well-demarcated neoplasm composed of an admixture of numerous delicate, thin-walled, capillary-sized vessels and plump AAM is most likely to be confused with AMF because they share many features including age at presentation, location, clinical manifestations and pathological features, but AAM has infiltrative margins, pauci-cellularity, large and thick-walled blood vessels and stromal mucin.They are potentially destructive lesions with a local recurrence rate of 30-50% (2, 6).On the other hand, superficial angiomyxoma has a more lobulated and distinct margin.Histologically it can be differentiated from AMF due to the hypocellularity and presence of delicate, elongated and thin-walled blood vessels (6).Cellular angiofibromas most commonly occur in the vulva.It also occurs at reproductive age and is a wellcircumscribed subcutaneous mass like AMF.However, unlike AMF it is more uniformly cellular and shows presence of large thick-walled vessels and perivascular hyalinization (2, 6).Fibroepithelial stromal polyp is typically an exophytic polypoid lesion with variable cellularity and shows the presence of large, thickwalled blood vessels within the central core (2).Mammary-type myofibroblastoma occurs typically after 40-years-of-age.Though it is well-circumscribed, it shows variable cellularity and is composed of bland spindle cells with short, stubby nuclei admixed with collagen bundles and adipocytes.It lacks the prominent vascular component of AMF (2, 6).SCVMF is more superficially located than AMF and composed of moderately cellular spindle, stellate to epithelioid cells with scant cytoplasm, arranged in a reticular pattern.They have inconspicuous vascularity (6).The perivascular clustering of cells in AMF may suggest a glomus tumor.However, glomus tumor has a uniform cellularity and is composed of sheets of round-shaped cells with indistinct borders and rounded, sharply punched-out nucleus and eosinophilic cytoplasm (2).
AMF has no risk of recurrence or metastasis, therefore; simple total surgical excision of the lesion is the treatment of choice.

Conclusion
In conclusion, AMF is a distinctive neoplasm of reproductive age females.A wide variety of lesions can present with similar clinicoradiological features.Recognition of this entity is important to avoid misdiagnosis and confusion with other vulval mesenchymal neoplasms.
round to spindle-shaped stromal cells.The spindleshaped cells are typically clustered around the prominent vasculature.The stromal cells have nuclei with fine chromatin and inconspicuous nucleoli and moderate amounts of eosinophilic cytoplasm; set within a variably edematous to collagenous matrix with alternating zones of cellularity.Occasionally, intralesional adipocytes may be present and lack mitoses.The stromal cells are typically desmin positive and show variable positivity for actin (1, 2, 6).Though the principal differential diagnostic consideration is AAM, other common vulval mesenchymal lesions include superficial angiomyxoma, cellular angiofibroma, fibroepithelial stromal polyp, mammary-type myofibroblastoma, superficial (cervicovaginal/vulvovaginal) myofibroblastoma (SCVMF) and glomus tumor (2, 6).