Fibroadenoma vulva: Experience based on FNA of vulvar lesion

INTRODUCTION

Vulval fibroadenoma is thought to be a mammary-like fibroepithelial lesion of uncertain histogenesis. It is an extremely rare slow-growing tumor, usually seen after puberty, between 20 and 80 years of age.^[1,2] To date, around 50–60 cases of ectopic benign breast lesions and 20 cases of ectopic malignant breast lesions have been reported in the literature.^[3] Although fibroadenomas occur very rarely in the vulva, they can be seriously considered in the differential diagnosis based on the cytomorphological features of fine-needle aspiration (FNA) biopsy of the mass. This is important to avoid unnecessary incisional biopsy before excision.

CASE REPORT

A 51-years-old woman presented with a painless vulval mass since one year, gradually increasing in size [Figure 1a]. On examination, swelling was 5 × 5 cm, mobile, pedunculated, well-defined, firm, and non-tender arising from the vulva. Magnetic resonance imaging of perineum was done and it was reported as a benign mesenchymal tumor [Figure 1b]. FNA cytology (FNAC) was performed and a Giemsa and PAP-stained smear were made. On microscopy, the smears were cellular showing sheets, clusters, and stag-horn patterns of benign ductal epithelial cells with overlying myoepithelial cells, along with the presence of many scattered bare nuclei and presence of fibromyxoid stroma in the background. There was no atypia noted in the cells, nor there was necrosis, or mitosis. Hence, a diagnosis of benign fibroepithelial lesion suggestive of fibroadenoma vulva was given and excision was advised [Figure 2a and b]. No cell block preparation was made as it was suspected to be a benign lesion clinically and radiologically.

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Figure 1:

(a) Clinical photograph showing a pedunculated, large, mobile, soft-tissue mass over the vulva and (b) a computed tomography scan shows a nodular homogenously enhancing lesion on the vulva, (marked with an arrow).

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Figure 2:

(a and b) Smears show a cohesive cluster of polygonal epithelial cells and overlying myoepithelial cells exhibiting focal tubular arrangements, with no pleomorphism or mitosis and necrosis along with fibromyxoid stroma. There is the presence of bare bipolar nuclei in the background. Cytomorphological features are of fibroadenoma vulva. Giemsa stain, ×100 (a), ×400 (b) (c and d) The excision biopsy section shows ductal epithelial cells in a pericanalicular pattern in the background of fibromyxoid stroma. The ducts were lined by bilayered epithelium, inner columnar epithelium, and outer myoepithelial cells. H and E stain, 100× (c); SMA, 100× (d).

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The specimen was excised and sent for histopathological examination for confirmation. On gross examination, a single globular encapsulated grey-brown soft-tissue piece measuring 7 × 4.5 × 3 cm was received. On serial sectioning, a firm grey-white solid tumor with slit-like areas and whorls was seen. Microscopy showed a peri-canalicular pattern of ducts, lined by bi-layered inner columnar to cuboidal and outer myoepithelial cells with the absence of atypia, necrosis, or atypical mitosis [Figure 2c]. There were also few cystically dilated ducts in the background of fibromyxoid stroma. These ducts showed continuous cytoplasmic staining for SMA and nuclear p63 staining in the myoepithelial cells [Figure 2d]. Therefore, a confirmative diagnosis of vulval fibroadenoma was made histopathologically. The patient was followed up and is doing well for the past 8 months after surgery.

DISCUSSION

Vulval fibroadenoma presents either as cutaneous or subcutaneous nodules measuring 0.8–6.0 cm.^[1] They are usually solitary on labia major and rarely can present as vulval cysts.^[4] Approximately 1–6% of the population may have aberrant mammary tissue in the vulva.^[2,3] It can either be asymptomatic or present as a painful lesion. The swelling increases during pregnancy and lactation, suggesting a role of hormone.^[1,2] Approxiamtely 1–6% of the population may have aberrant mammary tissue in the vulva.^[2,3] Hartung reported the first case of a fully formed mammary gland in the left labium.^[5] Most of the studies have been done on excision samples Kalyani et al. observed two cases of vulval fibroadenoma diagnosed on FNA.^[6] Divya reported three cases of fibroadenoma, two in axilla, and one in the vulval region diagnosed on cytology and further confirmed on histology in young women.^[7]

The histogenesis of vulval fibroadenoma is controversial. It either may arise from ectopic mammary tissue derived from a primitive embryological milk line that extends from the axilla to the groin with incomplete involution giving rise to ectopic mammary tissue along the embryonic milk line.^[8] The second and recent theory by Putte et al. suggests that the presence of specialized glands similar to mammary glands exists in the anogenital area normally and is similar to eccrine glands, called mammary-like anogenital glands, and found in the vulva.^[3]

The ectopic breast tissue expresses hormone receptors and has the potential to present with benign or malignant lesions similar to normal mammary tissue.^[2] The benign lesion seen is an epidermal cyst, follicular cyst, Bartholin’s gland duct cyst, lipoma, hidradenoma papilliferum, lactating adenoma, intraductal papilloma, phyllodes tumor, syringoma, fibroadenoma, fibrocystic disease, and sclerosing adenosis. Malignant lesions which can be seen at this location are extra-mammary Paget’s disease, ductal/lobular/mucinous adenocarcinoma.^[1]

Cytologically such lesions can mimic a few entities like hidradenoma vulva. The smear shows groups and sheets of benign glandular cells with a dual population of cells, one with a moderate amount of cytoplasm and the others and basaloid cells. The nuclei are eccentrically placed with a finely granular chromatin pattern and inconspicuous nucleoli. They resemble fibroadenoma, but fibroadenoma has a very characteristic fibromyxoid stroma long with many bare bipolar nuclei.

They may also look like low-grade adenocarcinoma or hidradenocarcinoma if they show overlapping clusters or atypia, but the lack of nuclear features, atypical mitosis, and necrosis rule out this. The differential of Paget’s disease can be considered due to the location of the lesion but the presence of prominent nucleoli is needed which was lacking in our case.^[8]

The role of cell-blocks compared to core biopsies is increasingly indicated in most cytology cases, especially with the use of immunohistochemical markers and the subtractive coordinate immunoreactivity pattern approach. It can also be used for many ancillary tests even as archived material. Shidham in their review introduced the term Cell Blockistry as the science of studying chemistry and the art of achieving improved quality cell blocks.^[9]

Histopathological features are similar to those in the breast. They present as a grey-white encapsulated lesion and whorl-like on cut section. Microscopy shows the presence of tubular or slit-like glands along with fibromyxoid stroma. The glands are arranged in pericanalicular or intracanalicular ducts lined by two layers of luminal columnar cells and abluminal myoepithelial cells with the presence of normal ductular structures adjacent to the lesion indicating its origin from ectopic breast tissue.^[1,2] These ducts are positive for ER, PR, SMA, S100, CK, and EMA. They are benign tumors with similar behavior as that seen breast. Excision usually has a good prognosis, with recurrence seen in 3% of cases.^[10]

CONCLUSION

Although fibroadenomas occur very rarely in the vulva, they can be seriously considered in the differential diagnosis based on the cytomorphological features of FNA biopsy of the mass. This case is presented not just because of its rarity but to highlight the importance, that a minimally invasive procedure like FNAC may help in the early diagnosis and an unnecessary incisional biopsy for confirmation can be avoided.