Discussion
EPC is a potentially lethal neoplasm. It was previously known as eccrine
adenocarcinoma or malignant eccrine poroma.6 The
origin of this tumor is from the intraepidermal and dermal eccrine
ducts.
Some etiological factors for EPC are radiotherapy, ultraviolet radiation
and immunosuppression with unknown pathogenesis.4 None
of these risk factors were present in our case. It is postulated that
the upper portion of the dermal eccrine duct could have a role in the
oncogenesis. The p53 gene involved in tumor suppressing could be
involved in EPC carcinogenesis.1
The clinical differential diagnoses include cutaneous squamous cell
carcinoma (SCC), cutaneous lymphoma, extramammary paget’s disease,
bowen’s disease, cutaneous metastasis, amelanotic melanoma, or other
primary skin appendageal tumors.6 Diagnosis of EPC is
difficult because of variable presentations and similar clinical and
histological features to cutaneous SCC,5 which was
differentiated by the presence of cuticles and positivity for EMA in our
case.
Mature duct formation, identified as the presence of ducts lined by
cuboidal epithelial cells commonly with an eosinophilic cuticle, was
found in 62%∼68% in previous studies.7 This
characteristic cuticle formation were also prominent in our case that
demonstrated EMA positivity in rim of ductules. (Fig 2F)
Histopathologically, factors associated with worse prognosis are mitotic
index >14/high power field (hpf), lymphovascular invasion
and tumor depth ≥7mm. Clinically, few factors which yield poor prognosis
are associated with local recurrences, regional lymph node and distant
metastases.8
Our case had ~20 mitosis/hpf, showed lymphovascular
invasion with ipsilateral axillary nodal metastasis and a tumor depth of
4cm all of which fares a poorer prognosis.