Adenoid Cystic Carcinoma of Salivary Gland: A Ten-Year Single Institute Experience

Abstract

Adenoid cystic carcinoma is a rare tumor, accounting for about 7.5% of all salivary gland neoplasms. More frequent developing in minor salivary gland, this is a slow-growing tumor with a long-lasting natural evolution, quite aggressive locally, but which has a tendency toward local recurrence and even for distant metastasis. We conducted a retrospective study limited to a period of 10 years in a single medical institution to investigate the morphoclinical profile of this tumor. Thus, we have established that about 60% of the tumors developed in men, with near 40% of the cases in patients in the sixth decade and, most common, the pathology affected the parotid and minor salivary glands from the hard palate mucosa. Histopathologically, prevailed the solid variant, with 72% cases presenting perineural invasion, and 41% cases showing positive surgical resection margins. Most cases had a long-standing asymptomatic evolution, so that at the time of diagnosis, more than two thirds of the patients were at least in stage II-pTNM, and in one-fifth of the cases histopathology showed lymph nodes disseminations.

Keywords: adenoid cystic carcinoma; epidemiology; histopathology; salivary gland.

Figure 1

Salivary gland adenoid cystic carcinoma (ACC). A. Predominance of small neoplastic cells with hyperchromatic, angular nuclei and scant clear cytoplasm, and with poorly defined cell borders. HE staining, x600; B. Solid variant of ACC consisting of sheets of basaloid cells without lumina formation. HE staining, x25; C. Tubular variant of ACC made of ducts and tubules, lined by luminal cells that were coated by non-luminal myoepithelial cells. HE staining, x50; D. Cribriform variant of ACC composed by oval to rounded masses of basaloid cells with scattered microcystic spaces, that usually are filled with pink or bluish material. HE staining, x25.

Figure 2

Salivary gland adenoid cystic carcinoma (ACC). A. Stroma between neoplastic proliferations was made of hyalinized fibrous tissue. Masson's trichrome staining, x100; B. Peri-and intraneural neoplastic cell invasion. HE staining, x100; C. Lymph nodes metastases from a solid variant of parotid ACC. HE staining, x25; D. Vein invaded by hard palate ACC. HE staining, x50.

Figure 3

Statistical analysis proving significant difference between the average age of patients with involvement of major salivary glands (54.31±13.85 years old), compared to those with tumors of the minor salivary glands (62.31±9.97 years old), t(30)=−1.87, p=0.035

Figure 4

Statistical analysis proving significant difference between the average age of patients with perineural invasion (54.00±13.80 years old), compared to those without perineural invasion (60.72±11.46 years old), t(30)=−1.65, p=0.048.