Microcalcifications in salivary gland tumors.

Salivary gland tumors form an informidable group of tumors with abundant tumor entities listed by World Health Organization (WHO). They can make diagnosis difficult because of morphological diversity in the tumor itself and between tumor types. Grey areas also exist between clear demarcation of benign and malignant tumors in some variants. Relative rarity of tumor types makes the assessment of natural history, biology of the tumor and prognosis difficult.

Few histological parameters like dedifferentiation and new histopathological variants have found recognition in the field of salivary gland tumor pathology, but some findings like microcalcification are yet to be completely explored.

Calcification, generally in the form of microcalcifications are seen in a range of salivary gland tumors from pleomorphic adenoma,[1] keratocystoma,[2] epithelial-myoepithelial carcinoma[3] to mucoepidermoid carcinoma (MEC) most frequently.[4] The presence of microcalcifications in salivary gland tumors is rare and the significance of its presence fades clarity. According to some reports, the presence of microcalcifications suggests that they are associated with high-grade tumors with more aggressive outcomes.[4] More recent articles clearly state that the calcifications is not related to histopathological grade of differentiations and is not associated with outcome either.[4] This phenomenon is more frequently seen in MEC of minor salivary glands, especially with clear cell differentiation. The calcifications seen are frequently concentric in nature and are more in intra-luminar ducts and cysts. The calcification may be concentric, laminar frequently and can be punctiform or irregular [Figure 2].[56]

Figure 2

Areas of microcalcifications with central basophilic zones and peripheral eosinophilic zones detected in different fields of MEC. Microcalcifications were seen among (a) Epidermoid and spindle shaped cells arranged irregularly (H&E stain, ×100). (b) At the center of epidermoid cells arranged oncentrically (arrows), few mucous cells are also seen (H&E stain, ×200). (c) Concentrically arranged among epidermoid cells (H&E stain, ×200). (d) Concentrically arranged among spindle and epidermoid cells (arrows) (H&E stain, ×100)

Concentrically arranged microcalcifications can be appreciated among spindle-shaped cells and epidermoid cells. Some of the epidermoid cells show cytoplasmic clearing [Figure 1a]. Hand-drawn illustration of the same can be seen in Figure 1b.

Figure 1

(a) Photomicrograph of MEC showing eosinophilic microcalcifications with concentric basophilic lines (arrows) (H&E stain, ×200). (b) Hand-drawn illustration of the same

All authors propose four mechanisms for the process of calcification. These include the following:[4].

Result of hypercalcemia

As a tumor component

Dystrophic calcification of necrotic area

Calcifications of the material secreted by tumor cells.

The latter two reasons are gaining more support, as in some cases it is seen as calcification of the mucin secreted by malignant cells or calcification associated with amorphous eosinophilic material secreted by intermediate basal cells.[5]

Although calcification is a common finding in inflammatory salivary gland disorders, their role or significance is rarely stressed in diagnosis of salivary gland tumors.[7] A detailed observation and correlation in larger number of salivary gland tumors may help in elucidating their role and relation to the pathology.