Acinic Cell Carcinoma (AcCC) of the Salivary Glands

• Acinic cell carcinomas (AcCC):

• Is the second most common malignant tumor:

• Involving the parotid gland

• They represent 15% of malignant parotid gland neoplasms

• AcCC accounts for approximately:

• 5% to 17% of all salivary gland tumors:

• 10% to 17% of all malignant salivary gland tumors

• The parotid gland is composed almost exclusively of serous type acini:

• And it is the most common site of AcCC:

• 80% to 90% of cases

• Other reported sites are:

• The palate (up to 15%)

• Submandibular gland (4%)

• Sublingual gland (1%)

• AcCC occurs most often in the fifth decade of life:

• Women are affected more often than in men (ratio 3:2)

• It is generally a low-grade carcinoma:

• With indolent behavior

• Recurrences are usually delayed:

• Sometimes after decades:

• In a series reported by Ellis et al:

• 12% of tumors recurred and 8% metastasized (bone, lung, and brain)

• The regional lymph nodes:

• Were the most common site of metastases:

• Spafford et al:

• Reported cervical lymphadenopathy to be present in 10% to 15% of cases of AcCC

• Spiro et al:

• In a series of 67 cases with AcCC treated before 1968, identified five cases (7.5%) with cervical metastases at the time of initial treatment

• It is interesting that this tumor is the most common bilateral malignant salivary gland neoplasm:

• Although its bilateral presentation is not nearly as common as the bilateral presentations of benign tumors:

• Warthin’s tumor and pleomorphic adenoma

• AcCC:

• Are typically encased in a fibrous capsule:

• Grossly resembling round circumscribed nodules with a tan surface

• The cut surface is solid but may show cystic degeneration and hemorrhage

• Histologically, there are five cell types:

• Serous acinar cells:

• Explaining the predilection for the parotid gland

• Cells with clear cytoplasm

• Intercalated ductal cell

• Nonspecific glandular cell

• Vacuolated cell

• The microscopic recognition of AcCC also requires a strong appreciation for its varied growth patterns:

• There are four histologic growth patterns:

• Solid

• Microcystic

• Papillary

• Follicular

• Caution must be taken not to misread the:

• Solid pattern as normal parotid parenchyma

• The papillary-cystic pattern as cystic mucoepidermoid carcinoma

• The follicular pattern as metastatic thyroid carcinoma

• Serous acinar differentiation:

• Is developed most fully in the acinic cell:

• These cells have dark round nuclei and granular purplish cytoplasm

• The diagnosis of AcCC may be difficult to establish:

• Especially when some other cell type dominates the histopathology picture

• Some examples of this are the predominance of clear cells might cause confusion with:

• Mucoepidermoid carcinoma, clear cell adenocarcinoma, and metastatic renal cell carcinoma:

• In these circumstances, the diagnostic acinic cells can be identified using a periodic acid-Schiff (PAS) reagent:

• Their cytoplasmic secretory granules are PAS positive and diastase resistant

• Overall survival has been crudely estimated to be about 84%:

• Survival at 5 years has been reported between 76% to 90%, but fell to 56% at 20 years:

• Emphasizing the need for long- term follow-up