Salivary Glands and Rare Head and Neck Lesions
Adenoid Cystic Carcinoma
Adenoid cystic carcinoma accounts for 3-5% of all salivary
gland tumors and occurs in both the minor and major salivary
glands. It is the most common malignant tumor in minor sali-
vary glands.29 It is a slow-growing malignant tumor but neural
invasion occurs early, producing paralysis of motor nerves in
about one third and pain in about one half of the patients.31,40
The remainder of the patients affected by this tumor usually
presents with asymptomatic swelling.
Adenoid cystic carcinoma has a high tendency for recurrence
after surgical removal, owing to its infiltrative growth pattern.
Distant metastases usually occur in the lungs and in bone,
whereas lymphatic metastases are less frequent.
The histologic picture of adenoid cystic carcinoma is varia-
ble. In its classic form, the tumor is composed of small uniform
cells arranged concentrically in a cribriform pattern around the
gland-like spaces filled with homogeneous material produced
by the tumor cells.41 A continuous spectrum is found from this
classic pattern to an equal mixture of cribriform and solid struc-
tures to a predominantly solid pattern.
The smear may show different patterns:
Clusters of cohesive small uniform epithelial cells
arranged around hyaline globules (Fig. 22.20A);
Tubular structures covered with uniform cells
(Fig. 22.20B); and
Solid fragments of tumor cells (Fig. 22.21A).
The hyaline mucoid globules and tubular structures are consid-
ered to be one major morphologic feature in establishing a diag-
nosis of adenoid cystic carcinoma in aspirates.42 In some cases,
they may be prominent, whereas in others they may be very few
or single globules. The individual cells are small and have round
or ovoid nuclei which in smears often are naked but a narrow
rim of cytoplasm may be present (Fig. 22.21B). The nuclei show
little variation in size and shape. The nucleoli usually are readily
visible and sometimes prominent.
Key features of adenoid cystic carcinoma
Spherical aggregates, rosette-like groups, papillary
structures or solid fragments of cancer cells;
Dispersed naked nuclei common;
Fig. 22.20 Adenoid cystic carcinoma. (A) Clusters of small uniform epithelial cells surrounding globules of homogeneous, acellular material (May-
Grünwald-Giemsa x LP). (B) Tubular structure and globoid formations covered with tumor cells (May-Grünwald-Giemsa x LP).
Fig. 22.21 Adenoid cystic carcinoma. (A) Solid tumor fragment with monomorphic cells (May-Grünwald-Giemsa x HP) (B) Spherical globules surrounded
by epithelial cells with rounded-to-oval nuclei and scanty cytoplasm (May-Grünwald-Giemsa x HP).