Metaplastic carcinoma of breast
refers to a heterogeneous group of neoplasms characterized by intimate
admixture of adenocarcinoma with dominant area of spindle cell, squamous cell
and/or mesenchymal differentiation. They constitute the rarest histological
variant of invasive ductal carcinoma. Adenosquamous carcinoma of breast is rare
tumours included in the last edition of WHO classification of breast cancers,
as a subtype of metaplastic carcinoma. It constitutes of 0.3% of all breast
cancers. Here, we report a case of adenosquamous variant of metaplastic
carcinoma of breast in a 61 years old female who presented with a lump in the
right breast. The present case highlights that although metaplastic carcinoma
of breast is rare, we should be aware of this possibility and include it in the
differential diagnosis whenever appropriate.
Keywords: Metaplastic, Adenosquamous, Carcinoma.
Metaplastic carcinoma refers to a heterogenous group of neoplasm
characterized by an intimate admixture of adenocarcinoma with dominant areas of
spindle, squamous and/or mesenchymal differentiation, accounting for less than
1% of all invasive carcinomas. 1
Adenosquamous carcinoma of breast are rare tumour included in WHO
classification of breast cancer, as a subtype of metaplastic carcinoma,
constituting 0.3% of all breast carcinomas. 2, 3 Adenosquamous carcinoma
is characterized by areas of well-developed tubule/gland frormation intimately
admixed with widely dispersed solid nests of squamous differentiation4.
Adenosquamous carcinoma are divided into low grade and high grade.
Low grade adenosquamous carcinoma has less nuclear anaplasia, do not
metastasize and have an overall good prognosis3. In contrast, high
grade adenosquamous are quite aggrresive and show lymph node metastasis at the
time of diagnosis.
A 61 years old female, presented with a lump in the right breast
for 8 months. Physical examination revealed a lump which was hard, measured 6×5
cm with nipple retraction and palpable ipsilateral axillary lymph nodes. The
contralateral breast and axillary nodes were normal.
Sonomammography revealed an ill-defined lesion in the upper right
quadrant with axillary lymphadenopathy (figure 1). Trucut biopsy confirmed the
diagnosis of invasive ductal carcinoma NOS following which she underwent
modified radical mastectomy and the specimen was sent for histopathological
On gross examination, radical mastectomy specimen measured 15x13x4
cm. Cut surface revealed a pearly white lesion in upper outer quadrant (figure
Microscopic examination showed foci of architecturally confluent
glandular formation with an adjacent desmoplastic stroma (figure 3). Also seen were tumor composed of nests,
jagged islands of mild to moderately pleomorphic cells with a squamoid
appearance (figure 4). There were foci of keratin pearl formation with a few
dyskeratotic cells. Ductal carcinoma insitu with solid and cribriform growth
pattern was also seen. The diagnosis of adenosquamous carcinoma was given.
The immunohistochemical staining showed triple negative for ER, PR,
and Her2 neu expression and showed strong positive for cytokeratin.
Adenosquamous breast carcinoma was first described by Rosen in 1987
and later in a follow up study by Van Hoeven in1993. 5 Adenosquamous
carcinoma presents as a palpable mass and has been found in women whose age
ranges from 31 to 87 years. 3
Adeosquamous carcinoma is difficult to diagnose from other benign and
invasive tumors on noninvasive investigations. On imaging only the benign
nature of the lesion is observed. These tumors do no exhibit much cytological
atypia, despite the infiltrative nature of these tumors, so making it difficult
to diagnose on cytology.
On trucut biopsy, the infiltrative nature of the tumor cannot be
observed. So, diagnosis is usually made histologically on excision biopsy
specimen6. At gross examination, adenosquamous carcinoma tends to
display a stellate or infiltrative configuration, with poorly defined borders.
Microscopically, the carcinomatous component is characterized by small
glandular structures, with rounded rather than angulated contours, and solid
cords of epithelial cells, which may contain squamous cells, squamous pearls or
squamous nests formation. The invasive neoplastic component typically shows
long, slender, extensions at the periphery and infiltrate in between the normal
breast structures, features which have been associated with inadequate local
excision and high incidence of recurrence.
Adenosquamous carcinoma is consistently negative for ER, PR
Her2-neu expression, hence may be a useful diagnostic tool. Myoepithelial and
cytokeratin stains are positive, but the extent of staining is highly variable.
SMA, p63, calponin and CD10 show variable degree of positivity. 2, 7
The study conducted by Khatib et al., who reviewed one case of
low-grade adenosquamous carcinoma of breast, showed triple negative for ER, PR,
Her2 neu expression. SMA and calponin were positive and highlighted the
myoepithelial cells, but p63 showed focal positivity. 8 Similarly,
our case showed triple negative for ER, PR, Her2 neu expression but showed
strong positivity for cytokeratin expression.
The study conducted by Geyer et al., who observed five cases of
adenosquamous carcinoma of breast, all of them belonged to 54 to 76 years of
age. 2 Similarly, our case was 61 years old.
The overall prognosis of adenosquamous carcinoma is good but it has
a tendency to locally recur depending on the adequacy of local excision. So,
complete local excision or mastectomy is usually recommended. Adenosquamous
carcinoma should always be differentiated from tubular carcinoma, infiltrating
syringomatous adenoma of the nipple and adenomyoepithelioma.
Adenosquamous carcinoma is a rare entity, has risk of local
recurrence after incomplete excision and has low metastatic potential. In
conclusion, adenosquamous carcinoma should always be kept in the differential
diagnosis whenever appropriate.