Morphological heterogeneity of oral salivary gland carcinomas: a clinicopathologic study of 41 cases with long term follow-up emphasizing the overlapping spectrum of adenoid cystic carcinoma and polymorphous low-grade adenocarcinoma

Abstract

We analyzed 41 oral salivary gland carcinomas from consecutive 290 salivary gland carcinoma database (14%) with emphasis on the histological spectrum and clinical outcome of adenoid cystic carcinoma (ACC) and polymorphous low-grade adenocarcinoma (PLGA). The cohort included 14 ACCs, 14 mucoepidermoid carcinomas (MECs), 8 PLGAs, 3 adenocarcinomas, not otherwise specified and 2 acinic cell carcinomas. Mean age was 48, 58 and 61 yrs for ACC, MEC and PLGA, respectively. Eight patients (19.5%) died of tumor at a mean interval of 66.5 months. ACC and PLGA showed similar mean age, gender distribution, predominant palatal localization, nodal metastasis, perineural invasion and MIB-1 index. However, ACC tended to show higher tumor stage and residual tumor (R1/R2) more frequently than PLGA, but this was statistically not significant. ACC and PLGA showed overlapping architectural patterns. However, ACCs displayed well organized basal-luminal differentiation, highlighted by CK5/CK7 immunostaining. In contrast, PLGA showed a disorganized histological and immunohistological pattern. C-Kit expression (CD117) was common in ACC, generally mirroring that of CK7 and virtually lacking in PLGA. Kaplan-Meier analysis demonstrated a similar clinical course for ACC and PLGA with 5 years survivals of 87% and 80%, respectively. Fluorescence in situ hybridization (FISH) performed on all 290 salivary carcinomas confirmed the specificity of the translocation t (11; 19) for MEC and its absence in all other carcinomas including ACC and PLGA. Our results emphasize the diversity of oral salivary gland carcinomas and the overlapping clinicopathological features of ACC and PLGA.

Keywords: Oral salivary gland carcinoma; acinic cell carcinoma; adenoid cystic carcinoma; polymorphous low-grade adenocarcinoma.

Figure 1

Architectural patterns of adenoid cystic carcinoma (left column) and polymorphous low-grade adenocarci-noma (right column). A/B Tubular pattern. C/D Cribriform pattern. E/F Solid pattern of “basophilic type". G/H Solid pattern of “clear cell type". I/J Trabecular pattern. K/L Reticular pattern. M/N Pattern reminiscent of invasive lobular carcinoma (ILC) of the breast (ILC like pattern/ indian file pattern). O Example of a dedifferentiated area (non specific pseudopapillary pattern) of ACC: high nuclear-cytoplasmic ratio, large nuclei and enhanced mitotic activity. P Papillary pattern of PLGA. Magnification 630× with oil immersion, HE staining.

Figure 1

Architectural patterns of adenoid cystic carcinoma (left column) and polymorphous low-grade adenocarci-noma (right column). A/B Tubular pattern. C/D Cribriform pattern. E/F Solid pattern of “basophilic type". G/H Solid pattern of “clear cell type". I/J Trabecular pattern. K/L Reticular pattern. M/N Pattern reminiscent of invasive lobular carcinoma (ILC) of the breast (ILC like pattern/ indian file pattern). O Example of a dedifferentiated area (non specific pseudopapillary pattern) of ACC: high nuclear-cytoplasmic ratio, large nuclei and enhanced mitotic activity. P Papillary pattern of PLGA. Magnification 630× with oil immersion, HE staining.

Figure 2

Different expression patterns of CK5, CK7, C-Kit and MIB-1 in normal salivary gland tissue (left column), adenoid cystic carcinoma (middle column) and polymorphous low-grade adenocarcinoma (right column). A/B/C HE staining. D/E/F Cytokeratin 5 staining. G/H/l Cytokeratin 7 staining. J/K/L C-Kit staining. M/N/O MIB-1 staining. Magnification 400×.

Figure 3

Expression of c-Kit in adenoid cystic carcinoma (ACC) and polymorphous low-grade adenocarci-noma (PLGA). Box plot analysis and double-sided t-test.

Figure 4

Kaplan-Meier survival analysis and log rank statistics of acinic cell carcinoma (AC), adenoid cystic carcinoma (ACC), polymorphous low-grade adeno-carcinoma (PLGA) and mucoepidermoid carcinoma (MEC).