3 | DISCUSSION
SCC accounts for 90% of tumors in hypopharynx. Other histological types
are relatively uncommon. As for ACC, it is extremely rare. Dysphagia is
one of the common symptoms related to ACC, especially for solids, which
are similar to SCC. Imaging studies, e.g. CT or MRI, contribute to
provide anatomic details that are useful for surgical planning, but not
to make differentiation from SCC. A tissue diagnosis is required to make
the diagnosis. Only few authors reported cases of ACC in hypopharynx.2,3
Furthermore, the pathologic features of basaloid squamous cell carcinoma
(BSCC) can be similar to that of ACC. BSCC generally displays certain
histological features, such as no presentation of bi-layered structures
and basophilic matrix, and diffuse immunopositivity for p63 and p40 in
tumuor cells revealed the absence of myoepithelial
elements.4 Although it is known that BSCC with adenoid
cystic-like features (BSCC-AdC) occurs more commonly in
esophagus5, BSCC-AdC also sometimes occurs in
hypopharynx.6
Bicomponent cancer of SCC and ACC also should be concerned for the
potential limitation of tissue biopsy. Unlike overlapping malignancy of
head and neck SCC and esophageal SCC, collision tumor of head and neck
was barely seen. But there was collision tumor of SCC and ACC in larynx
or hypopharynx reported before, even with synchronous esophageal
carcinoma like this case. 7,8 Complete histological
investigation of a neoplasm and affection on multicomponent tumors are
crucial in the successful diagnosis of a collision tumor.
To our knowledge, hypopharyngeal subsequent ACC following SCC is a rare
tumor not previously described. Pathology is needed to make the correct
diagnosis, and complete excision is currently the standard treatment
approach. Our case demonstrates that clinicians should be aware of the
possible ACC, even if a diagnosis of SCC was made before, because
different therapy strategy and oncological follow-up planning need to be
considered for these two tumor entities.