Fact-sheet: Adenoid cystic carcinoma
- Cylindroma
Updated on 04/05/2021 at 9:03 AM
View all RADEOS cases associated with this fact-sheet
Definition
Adenoid cystic carcinoma of the head and neck: Salivary gland tumor with slow but aggressive growth and a high propensity for recurrence.
Rare: 4 to 15% of all salivary gland tumors
Most common histologic type among the rare malignant tumors of the minor salivary glands (25-31%)
Location: oral cavity > submandibular gland > parotid gland > sinonasal cavities & nasopharynx
Clinical features
Slow evolution accounting for a long clinical latency: slow-growing mass
Pain and paresthesia (1/3) due to the tumor's propensity for perineural invasion.
Sinonasal symptoms are most often nonspecific, with nasal obstruction, epistaxis, and mass effect.
Lymphadenopathy is rare.
Extension:
- locoregional: perineural spread and skull base extension via the skull base foramina (rarely transosseous)
- hematogenous spread and distant metastases found in 25 to 50% of cases (lung, bone ++)
Ultrasound
Cervical lymphadenopathy (rare, approximately 15% of patients).
CT
Expansile mass, often heterogeneous after contrast administration.
Precise locoregional staging
Contrast administration is essential to assess for perineural infiltration:
- maxillary nerve V2 and mandibular nerve V3 for sinonasal locations
- facial nerve in cases of parotid involvement
Assessment for foraminal widening: foramen ovale, foramen rotundum, and stylomastoid foramen
Distant staging
Assessment for bone involvement
MRI
On T1-weighted images, the lesion is isointense, enhancing after gadolinium administration.
On T2-weighted images, signal intensity varies according to histologic subtype:
- Cribriform pattern: hyperintense
- Solid pattern: hypointense
Perineural spread manifests as:
- focal loss of foraminal fat,
- thickening and enhancement along the nerve branches.
Nuclear medicine
18FDG PET/CT: increased uptake related to the hypermetabolism of tumor cells and any secondary lesions.
Management
Depends on tumor stage.
Head and neck tumor board
Surgical resection
Combined with postoperative radiotherapy
Classification
Subtypes:
Cribriform (50%): the most characteristic and most common subtype, corresponding to nests of myoepithelial cells hollowed by pseudocysts whose lumen is continuous with the collagenous stroma.
Tubular (30%): the most differentiated subtype. Myoepithelial and ductal cells are arranged in cords.
Solid (10%): the least differentiated and most aggressive subtype. It is characterized by the near-complete absence of cylinders, with islands of basophilic cells showing marked mitotic activity.
TNM:
TX Primary tumor cannot be assessed
T0 No evidence of primary tumor
T1 Tumor ≤2 cm in greatest dimension without extraparenchymal extension
T2 Tumor >2 cm and ≤4 cm in greatest dimension without extraparenchymal extension
T3 Tumor >4 cm and/or tumor with extraparenchymal extension
T4a: tumor invading skin, mandible, ear canal, and/or facial nerve
T4b: tumor invading skull base and/or pterygoid plates, and/or encasing the carotid artery.
NX Regional lymph nodes cannot be assessed
N0 No regional lymph node metastasis
N1 Metastasis in a single ipsilateral lymph node ≤3 cm in greatest dimension
N2 Metastasis as:
N2a metastasis in a single ipsilateral lymph node >3 cm but ≤6 cm
N2b multiple ipsilateral lymph node metastases, all ≤6 cm
N2c bilateral or contralateral lymph node metastases ≤6 cm
N3 Metastasis in a lymph node >6 cm in greatest dimension.
M0 No distant metastasis
M1 Distant metastasis present
Differential diagnosis
Low-grade mucoepidermoid carcinoma
Acinic cell carcinoma without dedifferentiated component
Low-grade polymorphous adenocarcinoma
Cystadenocarcinoma/ Low-grade cribriform cystadenocarcinoma
Basal cell adenocarcinoma
Low-grade adenocarcinoma, not otherwise specified (NOS)
Clear cell adenocarcinoma
Epithelial-myoepithelial carcinoma
Carcinoma ex pleomorphic adenoma, noninvasive (intact capsule) or with minimal invasion (<1.5 mm)
Intermediate-grade mucoepidermoid carcinoma
Acinic cell carcinoma without dedifferentiated component with Ki-67 >10%
Cribriform and/or trabecular adenoid cystic carcinoma
Sebaceous carcinoma with mild to moderate atypia
High-grade mucoepidermoid carcinoma
Adenoid cystic carcinoma with solid component >30%
High-grade adenocarcinoma NOS
Salivary duct carcinoma
Dedifferentiated carcinoma
Massively invasive carcinoma ex pleomorphic adenoma
Large cell carcinoma
Small cell carcinoma
Squamous cell carcinoma
Sebaceous carcinoma with marked atypia
Mucinous adenocarcinoma