Adenoid cystic carcinomas are the most common cancer of the lacrimal gland, accounting for about 30%–50% of all lacrimal gland cancers.
Adenoid cystic carcinoma is a type of adenocarcinomaadenocarcinomaA cancerous (malignant) tumour that starts in glandular cells (cells that release substances such as mucus, hormones and lubricating fluids)., which is a type of cancer that affects glandular structures. Adenoid cystic carcinomas of the lacrimal gland occur most often in people between the ages of 30 and 60. They also occur in teenagers.
Adenoid cystic carcinomas may not cause any symptoms other than a slight fullness or swelling in the upper eyelid (where the lacrimal gland is located). Sometimes these tumours can cause double vision (diplopia), decreased vision and bulging or protrusion of the eye (called proptosis). Pain occurs when the tumour grows into the bone of the orbit or the nerves.
There are 5 subtypes of adenoid cystic carcinomas. These subtypes are based on the pattern of the cancer cells when viewed under a microscope:
Grading is a way of classifying lacrimal gland cancer cells based on their appearance and behaviour when viewed under a microscope. To find out the grade of a tumour, the biopsy sample is examined under a microscope. A grade is given based on how the cancer cells look and behave compared with normal cells (differentiation). This can give the healthcare team an idea of how quickly the cancer may be growing and how likely it is to spread.
The grade of adenoid cystic carcinoma is based on the degree of differentiation of cells and their rate of growth.
moderately differentiated; includes adenoid cystic carcinoma without solid (basaloid) pattern
poorly differentiated; includes adenoid cystic carcinoma with solid (basaloid) pattern
Grading plays an important part in planning treatment and can also be used to help estimate the prognosis (future outcome).
Staging is a way of describing or classifying a cancer based on the extent of cancer in the body. The most common staging system for carcinoma of the lacrimal gland is the TNM system. The International Union Against Cancer (UICC) uses the TNM system to describe the extent of many solid tumour cancers, including adenoid cystic carcinoma.
TNM stands for tumour, nodes, metastasis. TNM staging describes:
Primary tumour (T)
Primary tumour cannot be assessed.
No evidence of primary tumour.
Tumour is 2 cm (0.8 inches) or less in size and is limited to the lacrimal gland.
Tumour is more than 2 cm, but less than 4 cm (1.6 inches), in size and is limited to the lacrimal gland.
Tumour is more than 4 cm in size.
Tumour has spread from the lacrimal gland into the soft tissues of the orbit, including the optic nerve or globe of the eye.
Tumour has spread into the membrane lining the orbital bone (periosteum), the orbital bone or nearby (adjacent) structures.
T4a – Tumour has spread into the periosteum.
T4b – Tumour has spread into the orbital bone.
T4c – Tumour has spread into nearby structures, including the brain, sinus, pterygoid fossa or temporal fossa. The pterygoid fossa and temporal fossa are shallow depressions of bone on the side of the skull behind the orbit.
Regional lymph nodes (N)
Regional lymph nodes cannot be assessed
No regional lymph node metastasis
Regional lymph node metastasis
Note: The regional lymph nodes include those around the ear (preauricular nodes), lower jaw (submandibular nodes) and neck (cervical nodes).
Distant metastasis (M)
No distant metastasis
Recurrent adenoid cystic carcinoma means that the cancer has come back after it has been treated. It may recur in the same location as the original cancer or it may recur in another part of the body (metastatic adenoid cystic carcinoma).
There is no stage grouping for adenoid cystic carcinoma.
Adenoid cystic carcinomas of the lacrimal gland can be very aggressive tumours. The prognosis is better for non-basaloid subtypes of tumours, such as cribriform tumours. The survival rate varies based on the subtype of adenoid cystic carcinoma. The 5-year survival rate for people with non-basaloid tumours is about 70%. The 5-year survival rate for people with basaloid tumours is poorer (about 20%).
The prognosis is poorer if there is bone or nerve involvement. Adenoid cystic carcinomas of the lacrimal gland tend to metastasize to the central nervous system and the lung.
When possible, an adenoid cystic carcinoma of the lacrimal gland should be completely removed. Treatment usually involves surgery.
Radiation therapy may be used after surgery. This is because adenoid cystic carcinoma tends to recur locally after treatment.