WELL-DIFFERENTIATED ACINIC CELL-CARCINOMA OF SALIVARY-GLANDS ASSOCIATED WITH LYMPHOID STROMA

In a multicenter study, 69 acinic cell carcinomas of the salivary glan ds were identified, of which 12 constituted what the authors believe t o be a distinct subgroup, Their most noticeable feature was a dense ly mphoid stroma with well-developed germinal centers, surrounding a some times scanty epithelial component, which in each case had a microcysti c growth pattern, All these tumors were enveloped by a thin fibrous ps eudocapsule, thus mimicking an intraparotid lymph node containing a me tastasis, All 12 cases showed low MIB1 proliferative activity, with a mean index of 1.7% (range, 0.5 to 3.7), All patients remained well wit hout recurrence or metastasis in follow-up periods of 19 months to 14 years, A second subgroup of nine acinic cell carcinomas also possessed a heavy lymphoid stroma with germinal centers, but its distribution w as more patchy than in the first subgroup, and in addition, the fibrou s pseudo-capsule was incomplete or absent, In each case the epithelial growth pattern was other than microcystic, These tumors had significa ntly higher MIB1 indices (mean, 17%; range, 3.4 to 45), In contrast to the first subgroup, only three of nine patients remained well with no further disease. The other six patients developed recurrences or meta stases, and two died of disseminated cancer, In view of the clinical a nd pathological data, it is speculated that the tumor foci lacking lym phoid stroma in each of the second subgroup possibly represented a clo ne of high-grade malignancy arising within a low-grade acinic cell car cinoma with lymphoid stroma. Copyright (C) 1997 by W.B. Saunders Compa ny.