ARTICLE
Auteur(s) : Nidal A Obaidat, Ahlam A Awamleh, Danny M Ghazarian
Department of Laboratory Medicine and Pathobiology, University
of Toronto, University Health Network, Toronto General Hospital, EC
11-003, 200 Elizabeth Street, Toronto, ON, M5G 2C4, Canada
accepté le 10 Mai 2006
Mammary like glands (MLGs) are now recognised to be a normal
constituent of the skin in the anogenital region, including the
peri-anal skin. They are unique in having features of apocrine,
eccrine and mammary glands. Many adnexal lesions of the anogenital
area are now recognized to be of MLG origin. These include
adenoma/fibroadenoma, hidrocystoma, hidradenoma papilliferum,
extramammary Paget’s disease, and adenocarcinoma [1-3].The
occurrence of carcinoma arising in anogenital MLGs is believed to
be extremely rare [4-6], especially in the peri-anal skin [7]. Only
a few cases of carcinoma in situ of the MLGs have been reported [8,
9], all arising in the vulvar skin, and none in the peri-anal skin.
Herein, we describe the first report of a unique peri-anal adnexal
tumour showing histological features of a tubulopapillary apocrine
hidradenoma, with an area of adenocarcinoma in situ.
Case report
A sixty seven-year-old woman presented with an asymptomatic skin
tag over the peri-anal skin, which had been progressing over the
past few months. There was no history of pain or bleeding from the
lesion, and there was no significant past medical history. On
examination, the lesion was polypoid, measuring 1.3 cm in
maximum diameter. No other skin lesions were seen. The mass was
excised and sent for histopathological examination with a clinical
diagnosis of peri-anal skin tag. Multiple levels were examined,
showing an unremarkable non-ulcerated relatively normal epidermis.
The dermis contained a well-defined unencapsulated dermal lesion,
not connected to the overlying epidermis. It was composed of a
fibrous stroma, with ductulo-papillary structures lined by
epithelium ( (figure
1A) ), which was mostly composed of one or two layers of
cuboidal cells, with a peripheral single cell layer of
myoepithelium. Decapitation secretion, characteristic of apocrine
glands, was seen within the lumina. Epithelial hyperplasia was seen
in many areas. Other areas also showed a slightly
complex/cribriform growth pattern ( (figure 1B) ). A small area
within the lesion contained small ductal/tubular structures,
entrapped within the fibrous stroma ( (figure 1C) ). However,
this area showed no cellular atypia and was lined by myoepithelium,
and thus was not considered invasive tumour. At one edge of the
lesion, the epithelial hyperplastic cells showed cellular atypia
with central tumour necrosis ( (figure 1D) ), but with
smooth peripheral margin. Mitoses were noted in this region.
Invasion was not seen in the multiple levels examined. Using
immunohistochemical staining, the glandular epithelium was positive
for cytokeratin 7 (CK7) ( (figure 2A) ) and low
molecular weight keratin (LMWK, Cam 5.2) ( (figure 2B) ), but negative
for P63. The luminal cells stained positively for gross cystic
disease fluid protein 15 (GCDFP-15). Most of the peripheral spindle
cells stained positively for smooth muscle actin (SMA), Calponin,
and smooth muscle myosin heavy chains (SMMS), confirming the intact
peripheral layer of myoepithelial cells, including the area of
entrapped glands ( (figure 2C) ), and the area
of cellular atypia and tumour necrosis (carcinoma in situ
component) ( (figure
2D) ). Monoclonal carcino-embryogenic antigen (CEA) and
epithelial membrane antigen (EMA) stained the luminal surface
throughout the lesion. However, the tumour cells stained strongly
and diffusely for CEA in the in-situ component ( (figure 2E) ), and only
focally within the benign component of the lesion. EMA stained the
tumour cells only focally within both components ( (figure 2F) ). Estrogen and
progesterone receptors (ER and PR respectively) were equally but
variably expressed within the benign component ( (figure 2G) ) exhibiting
inter- and intra- glandular heterogeneity of expression. Both ER
and PR were negative within the in situ component ( (figure 2H) ). MIB1
immunostain (a proliferation marker) showed an increase in the
labelling index only within the area of the cellular atypia and
tumour necrosis, corresponding to the in situ component of the
lesion.
The morphological and immunohistochemical staining was
compatible with an adnexal apocrine tumour and is best described as
a tubulopapillary apocrine hidradenoma, with an area of
adenocarcinoma in situ. The lesion was completely excised.
Discussion
Tubular apocrine adenoma (TAA) occurs most commonly on the scalp as
a slow growing circumscribed dermal/subcutaneous nodule. However,
rare variants of TAA have been described in the vulva [10] as well
as in the peri-anal skin [11]. In the anogenital skin, apocrine
adenoma is believed to arise from MLGs [2, 12]. Apocrine adenomas
are characterized by adenomatous tubular and cystic structures,
having apocrine-like cytological features, lobular configuration,
and abundant fibrous stroma.
As TAA may be histologically indistinguishable from papillary
eccrine adenoma (PEA), the term ‘tubulopapillary hidradenoma’ has
been suggested by some authors to describe adnexal lesions
incorporating features of TAA and/or PEA, with a predominance of
eccrine or apocrine differentiation as the case may be [13, 14]. As
our case contained an adnexal apocrine lesion with tubulopapillary
configuration, this term was used to describe it. The absence of
typical “hidradenoma-like features”, distinguishes these tumours
from hidradenoma papilliferum where the tumour cells and the glands
are more closely arranged [3]. In addition, as in other reported
cases of tubulopapillary hidradenoma with apocrine differentiation,
the lesion in our case had irregularly shaped tubular structures
lined by two layers of epithelial cells, with decapitation
secretion evident in the lumina in many areas [13-15]. Other
features include cystically dilated spaces with occasional
intraluminal papillary projections. The tumour cells contain
Periodic Acid-Schiff (PAS) positive diastase-resistant granules,
and iron pigment. Occasionally, cytonuclear pleomorphism may also
be present, but without infiltrative margins. However, our case
differs from published cases of apocrine adenomatous lesions by its
location in the peri-anal skin, and by illustrating features of
adenocarcinoma in situ within the lesion. The presence, in our
case, of some glandular structures entrapped within a fibrous
stroma may be mistaken for an infiltrative carcinoma. However,
multiple sectioning did not reveal an invasive component, and
staining with different markers for the myoepithelial layer showed
no break up in its continuity [15, 16]. The immunohistochemical
pattern of estrogen and progesterone staining in our case is
interesting as it shows an inter- and intra-glandular variability
of expression within the tubulo-papillary part of the lesion, with
almost absence of staining within the carcinoma in situ component.
The reason for this heterogeneity of expression is unknown. The
presence of the cribriform growth pattern and the fibrous stroma is
reminiscent of fibroepithelial lesions of the breast, and this
finding lends further support that this lesion may have risen in
anogenital MLGs [11]. Although absent in our case, a helpful
feature in attesting MLG origin is the presence of “normal” MLGs in
the deep dermis and subcutaneous fatty tissue, in the vicinity of
the adnexal tumour of interest [3].
Since the findings in our case have not been described before,
the natural history of such a tumour is uncertain. However, the
lesion was completely excised, and there was no evidence of disease
recurrence or metastases eight months after complete excision.
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