Adenosquamous Carcinoma
Epidemiology and Etiology:
- 0.4-4.0 % of all lung carcinomas
- Smokers in the majority
Common sites:
- Periphery of lung usually
Gross features:
- Periphery of lung usually
- Central scar maybe
- Similar to other NSCLC
Histologic features:
- Both Squamous cell carcinoma and Adenocarcinoma
components, each comprising at least 10% of the tumour
(arbitrary) (cannot make a definitive diagnosis on biopsy)
- Two components may be separate, or may “merge
and mingle”
- Proportion of each may vary
- Degree of differentiation of each component is
variable and not interdependent
- If adenoCA component
is solid with mucin production, require > 5 mucin droplets per HPF
for diagnosis
- A component of large cell carcinoma may be
present and does not change the diagnosis
- Mets usually show the same combination of
squamous and glandular differentiation
- Amyloid-like stroma cases have been described
- DDx
includes:
- entrapment of alveolar or bronchiolar acinar
structures within a squamous cell CA
- squamous metaplasia of entrapped bronchiolar
structures within adenoCA
- mucoepidermoid
carcinoma
- low-grade is identical to salivary gland
counterpart
- high-grade (difficult to reliably distinguish
from adenosquamous in all cases):
- characteristic admixture of mucinous and squamoid cells
- proximal exophytic
endobronchial location
- areas of classic low-grade MEC
- absence of keratinization or squamous pearl
formation without overlying in situ SCC
- (?absence of) tubular, acinar, and papillary
growth pattern
Immunophenotype:
Marker:
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Sensitivity:
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Specificity:
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TTF-1
(confined to adenoCA component)
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- IHC
recapitulates both squamous and adenocarcinoma components (in separate
cell groups)
- Biopsy:
- If TTF-1 reactivity is present in one
population of tumour cells and another
population is positive for squamous markers, this may indicate the
possibility of adenosquamous carcinoma,
although this diagnosis can only be made based on a resection specimen
- If TTF-1 and p40 / p63 positivity is seen in
different populations of tumour cells, this is
more suggestive of adenosquamous carcinoma
than if the markers are coexpressed in the same
tumour cells
Molecular features:
Other features:
- Clinical presentation and behavior is similar to
adenocarcinoma
- Early metastases
- Poor prognosis (may be an independent poor
prognostic determinant at stage I-II)
References:
- Travis W et al, eds. WHO Pathology & Genetics: Tumours of the Lung, Pleura, Thymus, and Heart (2004)
- Travis et al.
WHO Classification of Tumours of the
Lung, Pleura, Thymus, and Heart, 4th ed. (2015)
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