The many faces of acinic cell carcinomas of the salivary glands: a study of 40 cases relating histological and immunohistological subtypes to clinical parameters and prognosis.

AIMS

To study the morphological heterogeneity of acinic cell carcinoma (ACC) in correlation with clinicopathological parameters.

METHODS AND RESULTS

Forty well-characterized ACCs were classified as solid (n = 20), microcystic (n = 15), papillary-cystic (n = 4) or follicular (n = 1), based on the dominant architectural growth pattern. Fourteen tumours exhibited eosinophilic/clear cell morphology and 18 tumours were rich in zymogen granules (so-called blue dot tumours). High-grade morphology occurred in five tumours. Based on cytokeratin (CK) 7 staining and in analogy to CK7 expression in normal salivary gland epithelia, three distinct histogenetic subtypes were recognized: acinar (CK7-negative; n = 13), ductular (diffuse CK7-positive; n = 11) and mixed ductulo-acinar (10-66% CK7-positive cells; n = 16). Most papillary-cystic tumours displayed ductular differentiation (P = 0.015), whereas blue dot tumours never did (P < 0.001). Analysis of relapse-free survival (RFS) revealed that Stage I tumours had the best prognosis without any relapse in 18 years follow-up (P = 0.06). High-grade tumours were associated with shorter RFS (P = 0.028). Concerning the histogenetic types, monophasic (pure acinar or ductular) tumours were associated with a significantly better RFS than mixed ductulo-acinar tumours (P = 0.008).

CONCLUSION

The results underscore the great histological diversity of ACC, and the value of histogenetic subtyping as an additional prognostic factor regarding RFS.