A 69-Year-Old Woman With a Vulvar Lesion

A 69-year-old woman presented with a subcutaneous sessile, soft tissue mass, palpable, and arising in the vulvar region adjacent to the interlabial sulcus. The mass was attached to the vulvar cutis and measured approximately 3.0 cm in diameter. It was nontender, nonulcerated, and freely mobile. No sinuses, erythema, or stretching of the overlying skin was seen. The lesion was excised and submitted for pathologic examination. Gross examination revealed that the specimen consisted of a 2.8 × 2.0-cm skin fragment excised to a depth of 3.0 cm, with a firm, pink, partially circumscribed mass. The lesion was inked and submitted for histopathologic examination.Microscopic examination revealed that the tumor was composed of a stromal proliferation surrounding epithelial-lined cystic spaces that were flattened and leaflike (Figure 1). The epithelial lining was predominantly secretory-type epithelium, which did not resemble a mammary or anogenital glandular type. No atypia or significant mitotic activity was present. The stroma was hypercellular, with spindle-shaped cells with pale, elongated, and pointed nuclei and scanty cytoplasm (Figure 2). Scattered mitotic activity (<3 mitoses per high-power field) was observed within the stroma (Figure 2, inset). No evidence of stromal overgrowth, necrosis, or areas of heterologous differentiation was seen. The tumor was not infiltrative and the surrounding connective tissue appeared normal. The attached skin did not show any significant pathologic changes and was not connected to the lesion in the specimen received.What is your diagnosis?Phyllodes tumor is more common in the breast, where it accounts for less than 1% of breast tumors. Phyllodes tumor is also known to occur in various other anatomical sites. This is a case report of a phyllodes tumor arising in the vulva of a 69-year-old woman. Using this case as an illustration, we discuss whether phyllodes tumor is a site-specific tumor requiring the presence of ectopic breast tissue for tumorigenesis. An alternate hypothesis, that highly specialized anogenital glands can mimic mammary tissue was proposed previously. The tissue distribution of phyllodes tumor as described in literature and other common differential diagnoses are discussed.Based on the classic morphology, a diagnosis of phyllodes tumor of the vulva was made. The most common site for phyllodes tumor is the breast, where it accounts for less than 1% of breast tumors.1 Previous reports have shown that extramammary phyllodes tumor can occur in ectopic sites, including vulva and axilla.1–4 This is consistent with ectopic locations for extramammary breast tissue along the milk line. Only a very few cases of phyllodes tumor of the vulva have been reported in literature, to our knowledge. However, other morphologically similar lesions have been reported variably as fibroadenoma5 or adenofibroma, perianal apocrine adenoma, intraductal papilloma, and “adenoma of anogenital mammary-like glands.”In many of the reported cases, an association with ectopic breast tissue—as seen in normal mammary ductular structures adjacent to, or in direct histologic contiguity with, the lesion, was presumed. However, this presumption that phyllodes tumors arise from distal components of the embryologic milk ridge has been challenged strongly by van der Putte.6 His initial report on mammary tissue of anogenital region7 contended that extension of the milk ridge into the vulva has not been convincingly demonstrated and that the milk-ridge theory does not explain tumors rising from the perianal region. In a separate paper, van der Putte and van Gorp8 postulated the presence of a specialized gland type that may mimic mammary glands.In accordance with van der Putte's theory, in our current case, we did not identify normal mammary type tissue in contiguity or surrounding the lesion. According to her history, the patient did not have any accessory breasts or supernumerary nipples in the vulvar region. These cases indicate that the presence of normal breast tissue is unlikely to be a prerequisite for the development of phyllodes tumors. This observation is further supported by the fact that phyllodes tumors with the classic morphology have been described in such varied locations as the prostate9 and seminal vesicle.10Vulvar phyllodes tumor should be distinguished from the rare Mullerian adenosarcoma of the cervix that secondarily involves the vulva.11 Mullerian adenosarcomas may also display the same leaflike pattern and may be considered to be on the malignant end of the spectrum of biphasic lesions, one of which is represented by the phyllodes tumor. Mullerian adenosarcomas, however, also display periglandular stromal condensation, stromal cellularity, and increased mitotic activity. Other less likely differential considerations include cutaneous adnexal lesions, such as papillary hidradenoma and syringoma (because of the papillary formation in the former and the fibrotic stroma of the later). Syringoma is characterized by small ductal structures lined by 2, frequently compressed, cell layers in a fibrotic stroma. Both lesions lack the broad leaflike pattern that is characteristic of the phyllodes tumor.The rarity of extramammary phyllodes tumors makes it difficult to define whether phyllodes tumor is a morphologically similar lesion arising from diverse histogenesis, or whether the designation of phyllodes tumor should be reserved specifically for lesions arising from mammary-type stroma and epithelium.