Adenoid cystic carcinoma (ACC) is the most common malignant epithelial tumor of the lacrimal gland, accounting for approximately 25-30% of all lacrimal gland epithelial neoplasms. Histologically, it shows cribriform (most common, 30-40%), tubular, and solid patterns; the solid pattern is associated with the worst prognosis. Clinically, it presents with rapidly progressive (usually <1 year) painful proptosis — pain results from perineural spread (particularly along trigeminal nerve branches) and bone destruction. Radiologically, it appears as an irregularly marginated, aggressive mass in the lacrimal fossa; bone destruction (not remodeling) and perineural spread are pathognomonic features. Prognosis is poor; 10-year survival is 20-30%. Distant metastases (lung, bone, brain) are common in late stages. Treatment includes wide surgical resection plus adjuvant radiotherapy; complete resection is difficult due to perineural spread and local recurrence rate is high (50-70%). Extension to the skull base and intracranial space is one of the most important prognostic factors.
Age Range
30-60
Peak Age
40
Gender
Equal
Prevalence
Rare
Adenoid cystic carcinoma originates from malignant transformation of intercalated duct cells and myoepithelial cells of the lacrimal gland. The most distinguishing biological feature of the tumor is its capacity for perineural invasion — tumor cells spread along nerve sheaths (particularly the lacrimal nerve and ophthalmic division of the trigeminal nerve), causing pain, and this spread is visualized on MRI as enhancement along the nerve. The mechanism of bone destruction is the tumor's aggressive growth rate and stimulation of bone resorption through matrix metalloproteinase (MMP) secretion — this is reflected in imaging as permeative or lytic bone destruction, distinct from the pressure erosion (remodeling) seen in benign tumors. In the solid histological pattern, the intercellular space is very narrow resulting in marked diffusion restriction (low ADC); in the cribriform pattern, pseudocystic spaces filled with mucopolysaccharide and basement membrane material produce intermediate-to-high T2 signal. MYB-NFIB gene fusion (50-80%) plays a key role in tumorigenesis and is a potential therapeutic target.
Bone destruction (not remodeling) combined with contrast-enhancing perineural spread along trigeminal nerve branches (V1) in a lacrimal fossa mass is the pathognomonic radiological combination of adenoid cystic carcinoma. Bone destruction reflects the tumor's aggressive growth pattern, while perineural spread reflects its capacity for nerve sheath invasion (neurotropism). This combination has definitive diagnostic value for differentiation from pleomorphic adenoma (bone remodeling, no perineural spread) and other orbital tumors. Perineural spread is optimally evaluated on contrast-enhanced fat-suppressed T1 MRI with thin-section technique.
On non-contrast CT, an irregularly marginated, heterogeneous density mass is seen in the lacrimal fossa. Bone destruction (lytic or permeative type) is the characteristic and most distinguishing CT finding — aggressive bone destruction is seen in the lateral orbital wall, frontal bone, and zygomatic bone. The mass is generally iso- to hyperdense relative to surrounding soft tissues, and internal calcifications are seen in 20-30% of cases. Obliteration of orbital fat planes indicates invasion into surrounding tissues. Compression and indentation of the globe is common. The mass may extend beyond the lacrimal fossa into the temporal fossa or intracranial space. Perineural spread may be suggested on CT by widening of nerve foramina (foramen rotundum, superior orbital fissure widening).
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An irregularly marginated mass measuring approximately ___ x ___ mm is identified in the lacrimal fossa with lytic bone destruction of the lateral orbital wall; evaluation of the superior orbital fissure and nerve foramina for perineural spread is recommended; findings are consistent with adenoid cystic carcinoma.
On contrast-enhanced CT, the mass shows moderate to marked heterogeneous enhancement. Solid tumor components enhance prominently while necrotic or cystic areas remain unenhanced. In the cribriform pattern, more heterogeneous enhancement is seen due to pseudocystic spaces; in the solid pattern, more homogeneous and prominent enhancement is observed. Linear enhancement along the nerve in areas of perineural spread may be seen — particularly the enhancement pattern extending from the lacrimal fossa along the ophthalmic division (V1) of the trigeminal nerve to the superior orbital fissure and cavernous sinus is pathognomonic. Extension to the orbital apex and intracranial space is best evaluated on contrast-enhanced series.
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On contrast-enhanced series, the mass demonstrates moderate to marked heterogeneous enhancement; linear enhancement along ___ is observed consistent with perineural spread.
On T2-weighted MRI, adenoid cystic carcinoma shows heterogeneous signal characteristics; the signal pattern varies according to histological subtype. In the cribriform pattern, pseudocystic spaces filled with mucopolysaccharide produce intermediate-to-high T2 signal while surrounding solid tumor tissue shows low-to-intermediate signal — this 'Swiss cheese'-like pattern provides a diagnostic clue. In the solid pattern, the mass shows more homogeneous low-to-intermediate T2 signal (dense cellularity). Invasion of surrounding tissues (orbital fat infiltration, extraocular muscle thickening and signal change) is assessed on T2. Perineural spread may be seen as thickening and increased signal of the affected nerve on T2. In areas of bone destruction, replacement of bone marrow signal with tumor signal is observed.
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On T2-weighted sequences, the mass demonstrates heterogeneous signal with intermediate-to-high signal pseudocystic areas amid solid tumor tissue; thickening and signal increase along ___ is consistent with perineural spread.
On diffusion-weighted imaging, adenoid cystic carcinoma shows marked diffusion restriction particularly in solid components. ADC values are low in solid tumor areas (0.6-1.0 × 10⁻³ mm²/s), reflecting dense cellularity. The most pronounced restriction is seen in the solid histological subtype. In the cribriform pattern, pseudocystic areas show higher ADC values while surrounding solid tumor tissue is distinguished by low ADC — this heterogeneous ADC map provides information about the tumor's internal architecture. DWI may provide additional diagnostic information as diffusion restriction along the nerve in areas of perineural spread. In treatment response monitoring, increase in ADC values indicates positive response.
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On diffusion-weighted imaging, marked diffusion restriction is observed in solid tumor components with low ADC values (___ × 10⁻³ mm²/s); this finding is consistent with dense cellularity and supports malignancy.
On contrast-enhanced fat-suppressed T1 MRI, adenoid cystic carcinoma shows prominent and heterogeneous enhancement. Solid tumor tissue enhances intensely while pseudocystic spaces of the cribriform pattern remain unenhanced. The most important contrast-enhanced MR finding is perineural spread: thin linear or nodular enhancement is seen along affected nerves (particularly V1 — lacrimal and frontal nerves). This perineural enhancement may extend from the lacrimal fossa to the superior orbital fissure, cavernous sinus, and Meckel's cave. Meningeal enhancement indicates intracranial spread. Extraocular muscle invasion is seen as increased enhancement and morphological distortion of the muscle. Contrast-enhanced MRI is the mandatory modality for assessment of full disease extent and surgical planning.
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On contrast-enhanced fat-suppressed T1-weighted sequences, the mass demonstrates prominent heterogeneous enhancement with linear enhancement along ___ consistent with perineural spread; extension to the cavernous sinus is assessed as ___.
On B-mode ultrasonography, an irregularly marginated, heterogeneously hypoechoic mass is identified in the lacrimal fossa region. Margins are generally poorly defined and sharp mass-tissue differentiation cannot be made due to invasion of surrounding tissues. Internal echo pattern is more homogeneously hypoechoic in the solid subtype while more heterogeneous with pseudocystic anechoic areas in the cribriform pattern. Compression and indentation/deformation of the globe can be assessed. Posterior acoustic enhancement is generally absent (solid mass characteristic). Calcifications may be seen as hyperechoic foci. US is inadequate for evaluating bone destruction and intracranial extension — therefore CT and MRI are mandatory as complementary modalities.
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On ultrasonography, an irregularly marginated, heterogeneously hypoechoic mass is identified in the lacrimal fossa region with globe indentation; CT and MRI are recommended for evaluation of bone destruction and intracranial extension.
On FDG PET-CT, adenoid cystic carcinoma generally shows avid FDG uptake (SUVmax: 5-15 range). The primary tumor is seen with intense metabolic activity in the lacrimal fossa. Linear or focal FDG uptake along the nerve may be seen in areas of perineural spread — however MRI is superior to PET-CT for detection of perineural spread. The most important role of PET-CT is distant metastasis screening: lung metastases (40-60%, most common), bone metastases, liver and brain metastases are evaluated. Regional lymph node involvement is relatively uncommon in adenoid cystic carcinoma (5-10%), with hematogenous spread predominating over lymphatic spread. SUVmax change is monitored for treatment response assessment.
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On FDG PET-CT, avid FDG uptake is observed in the lacrimal fossa mass (SUVmax: ___); evaluation for distant metastasis reveals ___.
Criteria
Histologically sieve-like structure with pseudocystic spaces filled with mucopolysaccharide; most common pattern (30-40%), intermediate prognosis
Distinct Features
'Swiss cheese'-like heterogeneous pattern on MRI: intermediate-to-high signal pseudocystic areas on T2 scattered amid solid tumor tissue; solid areas show restriction on DWI while pseudocystic areas show free diffusion; solid component enhances on contrast series while pseudocystic areas do not enhance
Criteria
Histologically predominant tubular/glandular structures; subtype with best prognosis
Distinct Features
Similar to cribriform pattern on MRI but with more organized tubular structures; intermediate signal intensity on T2; moderate and more homogeneous enhancement; diffusion restriction milder than cribriform and solid patterns; radiological distinction from cribriform pattern is difficult
Criteria
Histologically predominant solid tumor cell sheets, minimal pseudocystic spaces; subtype with worst prognosis (30% solid component threshold has prognostic significance)
Distinct Features
More homogeneous low-to-intermediate T2 signal on MRI; most pronounced diffusion restriction (lowest ADC values: 0.6-0.8 × 10⁻³ mm²/s); more homogeneous and prominent enhancement; 'Swiss cheese' pattern of cribriform type is absent; radiologically may resemble other malignant tumors (lymphoma, rhabdomyosarcoma); necrosis more common
Distinguishing Feature
Pleomorphic adenoma shows bone remodeling (expansion + sclerotic margin) without destruction; margins are smooth, capsule intact; clinically >1 year painless slow growth; no perineural spread. Adenoid cystic carcinoma shows bone destruction, irregular margins, <1 year painful rapid growth and perineural spread
Distinguishing Feature
Orbital lymphoma generally shows diffuse orbital infiltration with 'molding' pattern conforming to orbital structures (aggressive bone destruction rare); homogeneous iso-to-hypointense T2 signal; very marked diffusion restriction (ADC <0.7); homogeneous enhancement; bilateral involvement common; no perineural spread; unlike adenoid cystic carcinoma bone destruction is not expected
Distinguishing Feature
Rhabdomyosarcoma typically occurs in childhood (<10 years), can be in any orbital location outside the lacrimal fossa, may show rapid growth and prominent bone destruction; shows heterogeneous T2 signal, marked diffusion restriction and intense enhancement; perineural spread not as prominent as adenoid cystic carcinoma; age distribution is the most important clinical clue for differentiation
Distinguishing Feature
Orbital metastasis generally located outside lacrimal fossa (orbital bone, extraocular muscles); may be bilateral; history of known primary malignancy is critical clue; may show bone destruction but no perineural spread; heterogeneous enhancement on contrast MRI; multiple lesions strongly favor metastasis
Urgency
urgentManagement
surgicalBiopsy
NeededFollow-up
MRI every 3-6 months for first 2 years, then every 6-12 months; chest CT annually for lung metastasis screening; lifelong follow-up required due to late recurrence and metastasis riskAdenoid cystic carcinoma is the most aggressive malignant tumor of the lacrimal gland requiring urgent multidisciplinary approach. Treatment includes wide surgical resection (often including orbital exenteration or cranio-orbital resection) and adjuvant radiotherapy (proton therapy or IMRT preferred). Complete surgical resection is often not possible due to perineural spread and positive surgical margin rate is high. Local recurrence rate is 50-70%. Distant metastasis (especially lung) is common in late stages (40-60%) and may appear years after diagnosis. 5-year survival is approximately 50-70%, 10-year survival 20-30%. Solid histological pattern, presence of perineural spread, intracranial extension, and positive surgical margins are poor prognostic factors. Biopsy is required for diagnosis but should ideally be combined with definitive surgery.
Aggressive tumor requiring wide surgical excision and adjuvant radiotherapy. Local recurrence is common due to perineural spread. Late distant metastasis (lung) may develop. 5-year survival is approximately 50-60%.