Accurate typing of
amyloidosis is still a major issue for pathologists and clinicians. Besides clinical data and immunohistochemistry, the histologic distribution of
amyloid could represent a useful tool to prevent typing errors, such as the misdiagnosis of hereditary and senile
amyloidosis as light chain-related
amyloidosis (AL). Minor salivary gland biopsy (
MSGB) is a widely performed procedure for
amyloidosis diagnosis and typing. In the largest clinicopathologic series of
amyloid-containing
MSGB specimens to date, we investigated for the first time whether
amyloidosis subtypes can be distinguished according to their pattern of salivary
amyloid deposition. The histologic distribution and semiquantification of
amyloid within salivary tissue were thoroughly reassessed for each case using
Congo red-fluorescence. Clinical data were retrospectively collected. The cohort included 92 patients with
amyloid-containing minor salivary gland biopsies. The type of
amyloidosis was AL in 51 patients (55.4%), non-V30M mutant ATTR in 10 (10.9%), V30M mutant ATTR in 8 (8.7%),
serum amyloid A-derived
amyloidosis (AA) in 6 (6.5%), wild-type ATTR in 4 (4.3%),
gelsolin in 3 (3.3%), and unclassified in 10 (10.9%).
Amyloid was more abundant in AL and AA compared with ATTR
amyloidosis, because of more extensive basement membranes and vascular deposits. Conversely, non-V30M mutant ATTR and wt-ATTR were strongly associated with peculiar
amyloid nodules located in close contact with salivary excretory ducts, with a specificity of 91.7%. In conclusion, our study suggests for the first time that
MSGB, in addition to its high sensitivity for
amyloidosis diagnosis, is a simple and effective tool for the recognition of ATTR
amyloidosis.