Low-Grade Adenosquamous Carcinoma
Key Facts
Terminology
Subtype of metaplastic carcinoma consisting of well-formed tubules and nests of squamous cells in background of spindle cells
Clinical Issues
LGASC is an example of a triple negative carcinoma with good prognosis
Low incidence of lymph node metastases
Rare cases recur locally &/or metastasize
Macroscopic Features
These carcinomas form irregular masses that may be ill defined due to the diffuse infiltrative pattern into adipose tissue
LGASCs can range from 0.5-8 cm with typical size of 2 cm
Microscopic Pathology
Some carcinomas have been associated with sclerosing or papillary lesions or with adenomyoepithelioma
Ancillary Tests
All LGASCs are negative for estrogen and progesterone receptors as well as HER2
Basal cytokeratins are present in all cases
EGFR is positive in approximately 1/2 of cases
Top Differential Diagnoses
Syringomatous adenoma (SA) of nipple
Metaplastic breast carcinoma
Squamous cell carcinoma
Sclerosing adenosis and radial sclerosing lesions
Tubular carcinoma
 Low-grade adenosquamous carcinomas consist of well-differentiated squamous nests  as well as glands  . The carcinomas have a diffusely infiltrative pattern into adipose tissue. |
 The malignant epithelial cells are widely dispersed  and accompanied by a cellular spindle cell proliferation  . Some of the spindle cells are neoplastic, and some are reactive fibroblasts. |
TERMINOLOGY
Abbreviations
Low-grade adenosquamous carcinoma (LGASC)
Synonyms
Syringomatous squamous tumor
Definitions
Subtype of metaplastic carcinoma consisting of well-formed tubules and nests of squamous cells in background of spindle cells
CLINICAL ISSUES
Prognosis
Generally favorable
Low incidence of lymph node metastases
Rare cases recur locally &/or metastasize
LGASC is example of triple negative carcinoma with good prognosis
Core Needle Biopsy
Diagnosis can be difficult on core needle biopsy
Carcinoma can resemble radial sclerosing lesion
Squamous nests in stroma are uncommon findings in benign lesions
MACROSCOPIC FEATURES
General Features
Generally forms irregular masses
LGASC may be ill defined due to diffusely infiltrative pattern into adipose tissue
LGASCs can range from 0.5-8 cm with typical size of 2 cm
MICROSCOPIC PATHOLOGY
Histologic Features
Consist of both glandular structures and squamous cell nests
Nuclear pleomorphism is minimal, and mitoses are usually absent
Glandular structures are well formed
Shape of glands is rounded rather than angulated; angulated glands are more typical of sclerosing adenosis or tubular carcinoma
Double layer of cells is often present
Normal myoepithelial cell layer is not present
Squamous cell nests are usually solid
Nests may be comma- or tadpole-shaped
Cells may form keratin and keratin pearls
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