Fig. 11.1
Fibroadenoma. A biphasic tumor comprised of branching glandular structures within a fibrous stroma (Courtesy of Dr. Payal Kapur, Department of Pathology, University of Texas Southwestern Medical Center, Dallas, Texas)
Fig. 11.2
(a, b) Phyllodes tumor. (a). Leaflike projections are seen at low magnification. (b). A cellular stroma is seen at higher magnification (Courtesy of Dr. Venetia Sarode, Department of Pathology, University of Texas Southwestern Medical Center, Dallas, Texas)
Similar to the mammary counterpart, the epithelial component expresses epithelial markers (AE1/AE3, CK7), estrogen receptor (ER) and progesterone receptor (PR); and smooth muscle markers highlight the myoepithelial layer [8, 13]. Human papillomavirus (HPV) DNA has been shown to be negative in three vulvar fibroadenomas [18].
Differential Diagnosis
The architecture and stroma would be the main differentiating features between fibroadenoma and benign phyllodes tumor. Fibroadenoma would exhibit a fibrous paucicellular stroma, whereas benign phyllodes tumor has a more cellular stroma. PASH should be differentiated from its mimicker, the low-grade angiosarcoma, by the lack of cytologic atypia, mitotic activity, and erythrocytes [17].
Summary
Clinical Presentation
Present as asymptomatic nodules
Histologic Features
Fibroadenoma: a circumscribed tumor composed of branching glandular structures surrounded by a fibrous paucicellular stroma
Phyllodes tumor: leaflike projections and cellular stromal component with variable number of pleomorphic cells and mitosis
Differential Diagnosis
Vascular neoplasm for lesion with pseudoangiomatous stromal hyperplasia
Takeaway Essentials
Clinical Relevant Pearls
Vulvar fibroadenoma and phyllodes tumor are rare lesions arising from the anogenital mammary-like glands.
Enlargement during pregnancy may be seen due to lactating-like changes.
Pathology Interpretation Pearls
The number of stromal mitosis is the determining criterion in distinguishing benign from low-grade phyllodes tumor.
Immunohistochemical/Molecular Findings
The epithelial component expresses estrogen receptor.
Lactating Adenoma
Associated with pregnancy, lactating adenoma arises from the anogenital mammary-like glands in rare occasions [19]. They can be solitary or multiple and present as masses [20, 21].
Histologic Features
The lesion is circumscribed and comprised of densely packed round tubules lined by cells with cytoplasmic vacuoles and intraluminal eosinophilic secretion (Fig. 11.3a, b). The stromal component does not compress the ducts. Mitotic figures may be identified.
Fig. 11.3
(a, b) Lactating adenoma. A circumscribed proliferation of round tubules which are lined by cells with cytoplasmic vacuoles (Courtesy of Dr. M. Angelica Selim, Department of Pathology, Duke University Medical Center, Durham, NC)
Differential Diagnosis
Other lesions of anogenital mammary-like glands can exhibit lactational changes such as a fibroadenoma [11, 22].
Summary
Clinical Presentation
Rare lesion that presents as a mass during pregnancy
Histologic Features
Well-circumscribed lesion
Epithelial cells with cytoplasmic vacuoles
Differential Diagnosis
Other lesions of anogenital mammary-like glands with lactational changes
Takeaway Essentials
Clinical Relevant Pearls
Most of these lesions are alarming because of the detection of significant clinical changes in a short period of time.
Pathology Interpretation Pearls
Mitotic figures are not associated with aggressive behavior.
Immunohistochemical/Molecular Findings
In practice rarely are immunohistochemical stains used to diagnose these lesions.
Hidradenoma Papilliferum and Hidradenocarcinoma Papilliferum
Hidradenoma papilliferum was first reported by Worth in 1878 and characteristically occurs in the vulvar and perianal regions [23]. Initially thought to be derived from the apocrine glands [24], subsequent reports support that hidradenoma papilliferum (as well as tubular adenoma) are derived from anogenital mammary-like glands [25, 26]. Therefore, the term “mammary-like gland adenoma of the vulva” has been proposed; however, hidradenoma papilliferum is best conceptually compared to intraductal papilloma of the breast [4, 27]. In a recent review [28], hidradenoma papilliferum was the most common benign vulvar glandular neoplasm accounting for 60 % of the benign lesions.
It often presents as a solitary and asymptomatic nodule. The ages of the patients in large series range from 29 to 90 years with the mean of 50 years [27]. The sites of involvement include labia minora (50 %), labia majora (40 %), fourchette (7 %), and clitoris (3 %) [27]. This distribution mirrors that of anogenital mammary-like glands. Although HPV types 16, 31, 33, 53, and 56 have been identified within lesional tissue, the virus does not appear to play a causative role [17].
Histologic Features
Histopathologically, the tumor exhibits both a papillary and glandular architecture with interconnected anastomosing tubules. The inner epithelial cells are typically columnar with pale eosinophilic cytoplasm and are surrounded by a myoepithelial layer (Fig. 11.4a, b). Oncocytic (oxyphilic) metaplasia, clear cell change, predominantly solid growth, cystic change, sclerosing adenosis-like changes, and others can be seen [4, 17, 29]. Mitoses can be identified in both the epithelial as well as the myoepithelial components and are not indicative of aggressive behavior [30].
Fig. 11.4
(a, b) Hidradenoma papilliferum. (a). An intradermal tumor comprised of branching and anastomosing tubules which are lined by inner epithelial columnar cells and an outer myoepithelial cells. (b). Prominent apocrine metaplasia can be seen (Courtesy of Dr. M. Angelica Selim, Department of Pathology, Duke University Medical Center, Durham, NC)
The epithelial component is highlighted by a variety of keratins (AE1/AE3, CK5/6, CK15) [31, 32], ER [33], and GCDFP-15 [34]. The myoepithelial component would be stained with a number of myoepithelial markers (S100, smooth muscle actin, calponin) and interestingly nestin [32].
The literature cites five cases of ductal carcinoma in situ arising in association with hidradenoma papilliferum [35–38]. Histopathologically, these tumors are described to possess foci of crowded pleomorphic epithelial cells with hyperchromatic nuclei, prominent nucleoli, and abnormal mitotic figures. However, the retention of a myoepithelial layer is indicative of its in situ nature [36, 38].
Differential Diagnosis
When there is connection to the overlying epidermis, epidermal hyperplasia and prominent plasma cells infiltrate can mimic syringocystadenoma papilliferum.
Summary
Clinical Presentation
A solitary and asymptomatic nodule
Histologic Features
A papillary and glandular architecture with interconnected anastomosing tubules.
An inner epithelial and an outer myoepithelial layer.
Oncocytic metaplasia, clear cell change, predominantly solid growth, and cystic change can be seen.
Differential Diagnosis
Syringocystadenoma papilliferum
Takeaway Essentials
Clinical Relevant Pearls
Derived from anogenital mammary-like glands
Pathology Interpretation Pearls
Mitoses can be seen in both the epithelial as well as the myoepithelial components and are not indicative of aggressive behavior.
When cellular pleomorphism and severe cytologic atypia are seen, the diagnosis of hidradenocarcinoma papilliferum should be considered.
Immunohistochemical/Molecular Findings
The retention of a myoepithelial layer highlighted by smooth muscle actin or calponin is indicative of the in situ nature of the lesion.
Extramammary Paget Disease
First reported by Crocker [39] to affect the scrotum and penis, extramammary Paget Disease (EMPD) has since been documented in the vulva and perianal region [40]. EMPD can be either primary or secondary. Primary EMPD can be either an intraepithelial neoplasm with or without invasion, or as a manifestation of an underlying primary adenocarcinoma. The implicated cells of origin for primary EMPD include skin adnexa (eccrine or apocrine glands) and anogenital mammary-like glands [6], or possibly pluripotential stem cells [4, 41–43]. Chanda et al. [44] identified that 29 % of 197 EMPD cases were associated with an underlying malignancy arising in organs in proximity to the vulva. Through a mechanism reminiscent of mammary Paget disease, secondary EMPD is thought to originate from epidermotropic spread of malignant cells or within contiguous epithelium [45]. Many cases of vulvar secondary EMPD have been described in association with other gynecologic and genitourinary (bladder) neoplasms [40]. Furthermore, perianal Paget disease, which accounts for 20 % of EMPD cases [46], is strongly associated with adenocarcinoma of the anus and colorectum [47].
EMPD of the vulva predominantly affects women in the seventh decade [48–50]. The primary symptoms are pruritus and burning [48]. The labia majora is the most frequently involved site followed by labia minora and clitoris [50]. It presents as a relatively well-demarcated flat or slightly elevated erythematous or gray-white lesion, 1–20 cm in size [50, 51] (Fig. 11.5). “Triple” EMPD is a rare presentation in which the genital lesions are associated with synchronous or metachronous, uni- or bilateral axillary involvement [52]. The primary EMPD is with a high recurrence rate and rarely metastasizes, contrary to the secondary form [48]. Noninvasive EMPD has an excellent prognosis [53]. Studies have shown conflicting data regarding the presence of invasion and prognosis [54, 55]. A recent study using the SEER (Surveillance, Epidemiology, and End Results) Program identified a long-term increased risk of developing secondary malignancies in patients with invasive EMPD [56]. Surgical excision is currently the standard treatment [49].
Fig. 11.5
Extramammary Paget disease. An erythematous plaque is seen bilaterally on the vulva and extends to the perianal region
Histologic Features
The histologic features are similar in both primary and secondary forms, characterized by large pale cells arranged as single units and clusters or glands formed within the epidermis (Fig. 11.6a–c). The involvement of adnexa, most commonly hair follicles and ducts, is frequently seen in EMPD. A signet-ring appearance can be seen due to marked intracytoplasmic mucin accumulation. In EMPD in situ, the neoplastic cells are localized within the epidermis. Invasive EMPD is classified as microinvasive or invasive. In microinvasive cases, the tumor cells are seen in the stroma no deeper than 1 mm below the basement membrane [57].
Fig. 11.6
(a–c) Extramammary Paget disease. (a, b). A proliferation of polygonal neoplastic cells is seen within the epidermis and extending into hair follicular epithelium. (c). Tumor cells with abundant pale cytoplasm and vesicular nuclei are seen replacing the eccrine glands. Residual lumen is still visible in one of the glands – a clue for not misdiagnosis adnexal extension as invasion (Courtesy of Dr. M. Angelica Selim, Department of Pathology, Duke University Medical Center, Durham, NC)
Rarely, mammary-type ductal carcinoma, invasive or in situ, can be seen in EMPD. In the latter case, ductal carcinoma in situ (DCIS) appears to involve anogenital mammary-like glands, thus complicating the accepted terminology EMPD in situ used for designation of carcinoma cells confined to the epidermis.
The tumor cells in EMPD are usually positive for mucicarmine, Alcian blue, and periodic acid-Schiff with diastase. Primary EMPD lesions would typically exhibit a sweat gland phenotype (cytokeratin (CK) 7+/CK20-/gross cystic disease fluid protein (GCDFP)-15+), whereas secondary EMPD lesions would exhibit an endodermal phenotype (CK7+/CK20+/GCDFP-15-) [58] (Fig. 11.7). Co-expression of CK20 and CDX2 is indicative of secondary EMPD of colorectal origin [59, 60]. HER-2/neu and CDX2 have been found to be useful in distinguishing primary EMPD from secondary EMPD of anorectal adenocarcinoma [61, 62]. Although the expression can be variable, mucin core proteins such as MUC2 and MUC5AC might be helpful in distinguishing primary from secondary EMPD (see Vignette 3 at the end of this chapter) (Table 11.1). Uroplakin III has been demonstrated to be of help in identifying metastatic urothelial carcinomas [63]. It should be emphasized however that the burden of delineation between primary and secondary EMPD lies on the clinician.
Fig. 11.7
Extramammary Paget disease. The intraepidermal tumor cells strongly express cytokeratin 7
Table 11.1
Immunoprofile of primary and secondary extramammary Paget disease
Immunostain | Primary | Secondary colorectal | Secondary urothelial |
|---|---|---|---|
Cytokeratin 7 | + | −/+ | −/+ |
Cytokeratin 20 | − | + | + |
GCDFP-15 | + | − | − |
HER-2/neu | + | − | − |
CDX2 | − | + | − |
Uroplakin III | − | − | + |
p63 | − | − | + |
MUC5AC | + | − | − |
MUC-2 | − | + | − |
Our understanding of the genetic basis for EMPD is currently limited. The expression of HER-2/neu and androgen receptor indicates potential benefit from targeted therapy [62, 64]. However, fluorescence in situ hybridization demonstrates no evidence of HER-2 gene amplification [65]. Recently, the deleted in liver cancer-1 gene (DLC1) hypermethylation and mutations in oncogene PIK3CA with overexpression of PI3K protein have been shown in EMPD cases [66–68].
Differential Diagnosis
The differential diagnosis of EMPD includes both benign conditions such as vulvar Toker cells, mucinous metaplasia, vulva intraepithelial neoplasia, and malignant melanoma [69]. In a recent study of 56 patients, Shaco-Levy et al. [50] reported that a panel of pan-cytokeratin, CK7, CEA, and EMA labels 100 % of primary EMPD cases, while no cases stained with S100, HMB-45, and MART-1 distinguishing EMPD from malignant melanoma. The mucinous cells in mucinous metaplasia would lack cytologic atypia and replace rather than infiltrate the squamous epithelium as in EMPD (see Chap. 12). Careful examination would show that the neoplastic cells in EMPD are round and often with cytoplasmic mucin in contrast to the dysplastic keratinocytes seen in VIN.
Summary
Clinical Presentation
Affects mainly women in the seventh decade.
The labia majora is the most frequently involved site followed by labia minora and clitoris.
It presents as a relatively well-demarcated flat or slightly elevated erythematous or gray-white lesion.
Histologic Features
Large pale cells arranged in singly or in clusters within the epidermis.
Extension along the adnexal structures can be seen.
Microinvasion is defined when the tumor cells are seen less than one millimeter below the basement membrane.
Differential Diagnosis
Vulvar Toker cells
Mucinous metaplasia
Vulvar intraepithelial neoplasia with mucinous differentiation
Secondary EMPD
Malignant melanoma
Takeaway Essentials
Clinical Relevant Pearls
Primary EMPD is slowly progressive and rarely metastasizes, in contrast to the secondary form.
EMPD is frequently confused with eczematous process delaying the diagnosis.
Pathology Interpretation Pearls
Minimal inflammation is seen in association with EMPD.
Cytoplasmic mucin is seen only in EMPD and not in squamous cell carcinoma or malignant melanoma.
Immunohistochemical/Molecular Findings
Panel for primary EMPD: CK7, CK903, and S100
Panel for secondary EMPD: CK7, CK20, CDX2, and p63
Other Lesions of Anogenital Mammary-Like Glands
Uncommon benign lesions of the anogenital mammary-like glands include fibrocystic-like changes in the form of sclerosing adenosis, columnar cell lesions, ductal lesions, and various metaplastic changes affecting the epithelium and myoepithelium.
Other Carcinomas of Anogenital Mammary-Like Glands
Adenocarcinoma of Anogenital Mammary-Like Glands
First reported by Greene in 1936, there have been approximately 30–40 cases of adenocarcinoma of anogenital mammary-like glands reported in the literature to date [4, 70–76]. Anogenital mammary-like glands have been suggested in those cases as a likely origin due to their marked similarity to homologous mammary carcinomas. The labia majora is the most commonly involved site, and the mean tumor size is 2.5 cm [71]. Because of the rarity, varying treatment modalities, and relatively short follow-up periods in the original publications, it is difficult to draw firm conclusions regarding the natural history and prognosis of these neoplasms. As a group, primary mammary-type adenocarcinomas appear to be locally aggressive tumors. In one review, 60 % (12/20) of patients were found to have regional lymph node metastasis at the time of presentation [71]. Radical or hemivulvectomy has been the primary treatment in most cases [71].
Histologic Features
The presence of an in situ component, remarkable similarity to a mammary counterpart, or a transition zone between normal mammary-like glands and the carcinoma component is necessary to establish a diagnosis. The histopathology of these tumors varies from predominantly ductal to lobular, mixed ductal and lobular, tubulolobular, mucinous, and adenoid cystic-like [71, 73, 74, 77, 78]. The morphology of most cases is that of an invasive ductal carcinoma [71] (Fig. 11.8a, b).
Fig. 11.8
(a, b) Adenocarcinoma of mammary-like glands. An infiltrative carcinoma resembling mammary ductal carcinoma is seen
Differential Diagnosis
The differential diagnosis includes extramammary Paget disease, sweat gland carcinoma, and metastatic adenocarcinoma to the vulva. Without clinical history, it would be difficult to distinguish adenocarcinoma of anogenital mammary-like glands from metastatic carcinoma from the breast since both have similar histology. Expression of ER and PR has been variable in adenocarcinoma of mammary-like glands [71, 76].
Summary
Clinical Presentation
The labia majora is the most commonly involved site.
Histologic Features
Varied from predominantly ductal to lobular, mixed ductal and lobular, tubulolobular, mucinous, and adenoid cystic-like
Differential Diagnosis
Extramammary Paget disease, sweat gland carcinoma, and metastatic adenocarcinoma to the vulva
Takeaway Essentials
Clinical Relevant Pearls
An aggressive tumor with 60 % of patients presented with nodal metastasis
Pathology Interpretation Pearls
Transition zone between normal mammary-like glands and the carcinoma component confirms the diagnosis.
The histology of most cases is that of an invasive ductal carcinoma.
Immunohistochemical/Molecular Findings
Can express estrogen and progesterone receptors
Other Adnexal Neoplasms
Syringoma
Syringoma was first described in 1874 by Kaposi and Biesiadeki as “lymphangioma tuberosum multiplex”; however vulvar involvement was not reported until 1972 [79]. Since then isolated cases and small case series of syringomas on the genital region have been reported [80–88].
Vulvar syringomas mostly occurred in young women in the third decade [81]. In a series of 18 vulvar syringomas from Taiwan, 11 lesions presented as multiple skin-colored, smooth-surfaced or brownish papules on the labia majora [81]. Discrete whitish cystic papules were seen in three patients [81]. Pruritus was the most commonly presenting symptom [81]. The size has been reported to increase during summer month or menstruation. Rare report of familial history has been documented [80].
Some have hypothesized that the growth of syringoma is under hormonal influence [82, 83]; however, staining for estrogen receptor (ER) and progesterone receptor (PR) was negative for all 15 studied cases by Huang et al. [81] and the case reported by Trager et al. [84]. Reported treatment for vulvar syringomas includes carbon dioxide laser treatment [81, 86], cryotherapy [87], electrosurgery [88], and excision [83].
Histologic Features
The lesion is typically a well-circumscribed proliferation of small ductal structures that are evenly distributed in a collagenous stroma (Fig. 11.9). The geometric ductal structures such as “comma-like” or “tadpole-like” are characteristic features. Clear cell change can be seen in tumors associated with diabetes mellitus and Down syndrome [89]. Extension into the deep dermis and subcutaneous tissue is typically seen in the plaque-type syringoma. Vulvar syringoma can be encountered as an incidental finding in association with melanocytic nevi, lichen sclerosus, and lichen simplex chronicus.
Fig. 11.9
Syringoma. A proliferation of small ductal structures is seen evenly distributed in a collagenous stroma. The overlying epidermis exhibits lichen simplex chronicus changes – hyperkeratosis, epidermal hyperplasia, and hypergranulosis
Differential Diagnosis
The differential diagnosis of deep or plaque-type vulvar syringoma would include microcystic adnexal carcinoma [95, 96]. (See Vignette 1 at the end of this chapter.) A sharp demarcation between the deep syringoma and the adjacent dermis or subcutaneous tissue would not be seen in microcystic adnexal carcinoma.
Summary
Clinical Presentation
Multiple skin-colored or brownish papules on the labia majora
Histologic Features
A well-circumscribed superfi cial proliferation of small ductal structures that are evenly distributed in a collagenous stroma
Differential Diagnosis
Microcystic adnexal carcinoma
Takeaway Essentials
Clinical Relevant Pearls
Pruritus is the most common presenting symptom worsening in summertime and menstruation.
It can be confused with HPV lesions.
Pathology Interpretation Pearls
Often an incidental finding in association with melanocytic nevi, lichen sclerosus, and lichen simplex chronicus
Hidradenoma
Clear cell hidradenoma usually presents as a solid and cystic nodule with no site predilection, though is only rarely reported to occur on the vulva [28, 97–99]. There have been rare case reports of vulvar hidradenocarcinoma [100–102]. Approximately 50 % of hidradenoma possesses the t(11;19) translocation [102]. HER-2/neu amplification has been reported in a case of metastasizing hidradenocarcinoma [103]; however, this finding has not been confirmed by subsequent studies [102, 104, 105]. Mutations of TP53 [102, 104, 105], PIK3CA [105], and AKT-1 [105] have been documented in rare cases of hidradenocarcinomas.
Histologic Features
Hidradenoma is characterized by multilobulated, circumscribed yet unencapsulated tumor (Figs. 11.10 and 11.11). Glandular structures can be seen, and in some cases these are striking. The tumor cells are diverse and can be clear, eosinophilic, squamoid/epidermoid, mucinous, oxyphilic/oncocytic, and transitional/intermediate [24]. Stroma is often hyalinized and sclerotic.
Fig. 11.10
Hidradenoma. A cystic and solid neoplasm comprised of clear as well as eosinophilic neoplastic cells is seen
Fig. 11.11
Hidradenoma. A cystic and solid neoplasm comprised of clear as well as eosinophilic neoplastic cells is seen
Differential Diagnosis
When focal infiltrative architecture and increased mitotic figures are seen, it is classified as atypical hidradenoma [106], whereas hidradenocarcinomas are characterized by infiltrative growth pattern, deep extension, necrosis, nuclear pleomorphism, and greater than 4 mitoses per 10 high-power fields [106]. Although in some rare instances, metastasizing hidradenocarcinomas do not show these histopathologic features [102]. Apparently, both high-grade and low-grade variants of hidradenocarcinoma exist [107].
Summary
Clinical Presentation
A solid and cystic nodule
Histologic Features
Glandular structures and tumor cells with eosinophilic, clear, or mucinous cytoplasm.
Stroma is frequently sclerotic and hyalinized.
Differential Diagnosis
Atypical hidradenoma
Hidradenocarcinoma
Takeaway Essentials
Pathology Interpretation Pearls
Hidradenocarcinomas are characterized by infiltrative growth pattern, deep extension, necrosis, nuclear pleomorphism, and greater than 4 mitoses per 10 high-power fields.
Immunohistochemical/Molecular Findings
Ki-67 index can be helpful in distinguishing atypical and malignant from benign hidradenoma.
Sebaceous Carcinoma
Although sebaceous glands can be prominent on the vulva, there have been only few cases of sebaceous carcinoma reported at this site [108–114]. The case reported by Jacobs et al. [110] was associated with colonic adenocarcinoma, likely in the setting of Muir-Torre syndrome. Two cases were associated with overlying Bowen’s disease [110, 111].
Histologic Features
Histologically, sebaceous carcinoma is characterized by an infiltrative proliferation comprised of pleomorphic basaloid cells with focal sebaceous differentiation. Ductal structures with eosinophilic cuticle, characteristic of sebaceous ducts, can be seen in well-differentiated sebaceous tumors (Fig. 11.12a, b). Vascular and perineural invasion can be seen. A panel of 2 mismatch repair proteins (PMS2 and MSH6) has been shown by one group to be as effective as a four-antibody panel (PMS2, MSH6, MSH2, and MLH1) as screening panel in detecting Lynch or Muir-Torre syndromes [115]. Vulvar sebaceous lesions however are rarely, if ever, associated with the syndrome. Recently, adipophilin has been shown to be a helpful marker in distinguishing sebaceous carcinomas from mimics [116, 117] (Fig. 11.13).
Fig. 11.12
(a, b) Sebaceous carcinoma. (a). An infiltrative carcinoma with sebaceous differentiation is seen. (b). Cytoplasmic lipid vacuoles are noted at higher magnification
Fig. 11.13
Sebaceous carcinoma. The abundant cytoplasmic lipid vacuoles are highlighted by adipophilin immunostain
Differential Diagnosis
Sebaceoma has rarely been reported in the vulva [28]. When a tumor exhibits multiple nests of basaloid cells with scattered mitoses but lacks the atypia of sebaceous carcinoma, it is classified as a sebaceoma.
Summary
Clinical Presentation
Rarely present on the vulva
Histologic Features
An infiltrative tumor comprised predominantly of basaloid cells and focally sebaceous differentiation
Differential Diagnosis
Sebaceoma
Takeaway Essentials
Clinical Relevant Pearls
Vulvar sebaceous lesions however are rarely, if ever, associated with Muir-Torre syndrome.
Pathology Interpretation Pearls
The sebaceous changes can be focal; therefore, examination of the entire lesion increases the chance of finding the diagnostic areas.
Immunohistochemical/Molecular Findings
PMS2 and MSH6 have been shown to be as effective as a four-antibody panel (PMS2, MSH6, MSH2, and MLH1) as screening panel in detecting Lynch or Muir-Torre syndrome.
Adipophilin can be helpful in highlighting the sebaceous differentiation.
Poroma
Poroma is often present on plantar or palmar skin; however, it may be found on any area containing sweat glands [118]. Rare cases of vulvar poroma have been reported with the frequency of 2.2 % of benign vulvar adnexal neoplasms [28].
Histologic Features
The tumor exhibits a proliferation of uniformly round (poroid) cells and eosinophilic squamoid (cuticular) cells (Fig. 11.14). Small ductal structures lined by an eosinophilic cuticle (highlighted by periodic acid-Schiff (PAS), epithelial membrane antigen (EMA), and carcinoembryonic antigen (CEA)) are often seen. It is generally accepted that poromas encompass the following tumors: classic poroma, hidroacanthoma simplex, dermal duct tumor, and poroid hidradenoma depending on the architecture of the neoplasm.
Fig. 11.14
Poroma. An intraepidermal proliferation of uniformly round cells
Studies have suggested that poroma derives from the basal keratinocytes of the sweat duct ridge and of the lower acrosyringium [119]. A panel of CK7 and CK19 has been shown to be helpful in differentiating porocarcinoma from squamous cell carcinoma [120].
Loss of heterozygosity in the APC gene has been shown in 3/7 poromas; however, this finding is of uncertain significance [121].
Differential Diagnosis
Porocarcinoma of the vulva is very rare with few cases reported in the literature [122–125]. They often affect women in the sixth decade. Similar to porocarcinomas at nongenital sites, they are associated with frequent nodal metastases [122–125]. One should keep in mind that porocarcinoma is likely to be overdiagnosed or even misdiagnosed, as the analysis of the histological images and descriptions of published “porocarcinomas” strongly suggests.
Summary
Clinical Presentation
Poroma may be found on any skin area with sweat glands.
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