Why is the histomorphological diagnosis of tumours of minor salivary glands much more difficult?

AIMS: There is a widespread perception among clinicians and pathologists that the histomorphological assessment of minor salivary gland (MinSG) tumours is more difficult and hampered by more misdiagnoses than that of major salivary gland tumours. This is based on a vague, subjective clinical impression, lacking scientific proof. The aim of the present study was to identify and statistically verify potential reasons that could explain this difference. METHODS AND RESULTS: We identified 14 putative clinical, pathological and combined clinicopathological reasons that, altogether, could explain the phenomenon of the perceived greater diagnostic difficulty associated with MinSG tumours. We performed a comprehensive literature search and a statistical comparison of data from a large personal consultation series (biased for difficult cases) with cumulated data from straightforward, unselected (non-consultation) series from the literature. By performing this comparison, we identified, with statistical significance, a comprehensive series of reasons, as well as of consequences, of the greater difficulty in diagnosing MinSG tumours. CONCLUSIONS: Among the 14 criteria, high frequencies of initial incisional biopsies and of a low-grade category in malignant tumours emerged as the two most important reasons for enhanced diagnostic difficulty. Very rare entities, unusual locations, shortcomings in clinicopathological communication, and pecularities of the special anatomical location of the hard palate, such as tumour necrosis, mucosal ulceration, pseudoinvasion, and the peculiar phenomenon of 'tumoral-mucosal fusion', contribute to further diagnostic difficulties. The awareness of these shortcomings and pitfalls enables us to provide a series of recommendations for clinicians and pathologists that might aid in assessment and reduce the rate of misdiagnosis of MinSG tumours.

Salivary ghost cell carcinoma: case report and proposal of a new entity.

Various topographically heterogeneous, histologically related groups of basaloid tumours are characterized by ghost cell differentiation with associated CTNNB1 mutations and nuclear ß-catenin expression. We describe the unique case of a malignant tumour with ghost cell differentiation in the floor of the mouth, in which clinical, radiological, histological, immunohistological and molecular data altogether strongly indicate classification as a new type of salivary gland carcinoma.

Pathologic reporting and special diagnostic techniques for melanoma.

Pathologists play a central role in the management of cutaneous melanoma in determining that a tumor is a melanoma, whether or not it is primary or metastatic, and whether or not the margins of excision are tumor free and in evaluating prognostic indicators from examination of the primary tumor and, where appropriate, lymph nodes, including the sentinel nodes.

Combined application of RT-PCR and immunohistochemistry on paraffin embedded sentinel lymph nodes of prostate cancer patients.

The detection of tumor cells in the sentinel lymph node (SLN) is of great importance for the prognosis of cancer patients. At present, immunohistochemistry and RT-PCR for tumor marker expression are the most sensitive techniques available for this analysis. However, so far, most RT-PCR-based analyses of SLNs have been performed on fresh material, excluding a direct comparison with the (immuno)histologic results. In our view, this does not entirely aid routine diagnosis. We established an efficient method for RNA extraction and RT-PCR from paraffin sections of SLNs from prostate cancer patients and compared the results with the (immuno)histologic data of adjacent sections. Amplifiable RNA was obtained from 133 SLNs of 68 prostate cancer patients. Correlation of PSA-specific RT-PCR with (immuno)histologic findings showed a positive and negative predictive value of 83% and 100%, respectively, for the prostate cancer patients investigated. Four of 12 patients with biochemical relapse, but without (immuno)histologically detectable tumor cells were RT-PCR-positive for PSA. We found that single sections of paraffin-embedded SLNs are suitable for routinely performed RT-PCR. Combined with (immuno)histology, PSA-specific RT-PCR is a revealing supplementary technique for the detection of tumor cells in SLNs of prostate cancer patients.

Tyrosinase RT-PCR as a supplement to histology for detecting melanoma and nevus cells in paraffin sections of sentinel lymph nodes.

The detection of tyrosinase mRNA in sentinel lymph nodes (SLNs) by reverse transcription polymerase chain reaction (RT-PCR) is a sensitive indicator for the presence of melanoma or nevus cells, but it does not enable a distinction between both. We have established an efficient method for extraction and reverse transcription of tyrosinase mRNA from paraffin sections that permits the close correlation of the RT-PCR results with (immuno)histologic findings in adjacent sections. One hundred fifty-three SLNs and 6 non-SLN specimens originating from 92 melanoma and 4 nonmelanoma patients were studied to test the reliability of this approach. The predictive value of positive RT-PCR results was 0.98 for the presence of melanoma or nevus cells; the corresponding negative predictive value was 0.83. Furthermore, the detection rate of tyrosinase mRNA significantly correlated with tumor burden. Among the 33 melanoma-positive SLNs without nevus cells, positive RT-PCR results were obtained in all specimens with extended peripheral (S2) or deeply invasive (S3) micrometastases but in only 46% of the cases with few localized melanoma cells in the subcapsular zone (S1). Routine (immuno)histologic evaluation alone had missed microclusters of melanoma cells in one SLN and small nevus cell aggregates in six other SLNs. They were detected only during microscopic reexamination caused by a positive RT-PCR result. We conclude that histology and immunohistochemistry remain the indispensable gold standard for the identification of melanoma and nevus cells in SLNs. Additional molecular analyses using adjacent paraffin sections may further improve the diagnostic accuracy by sensitizing and guiding the microscopist's attention.

Molecular analysis of skeletal tuberculosis in an ancient Egyptian population.

A paleomicrobiological study was performed on 37 skeletal tissue specimens from cadavers in the necropolis of Thebes-West, Upper Egypt, (2120-500 BC) and four from the necropolis of Abydos (3000 BC). The subjects had typical macromorphological evidence of osseous tuberculosis (n = 3), morphological alterations that were not specific, but probably resulted from tuberculosis (n = 17), or were without morphological osseous changes (n = 21). DNA was extracted from these bone samples and amplified by PCR with a primer pair that recognised the Mycobacterium tuberculosis complex insertion sequence IS6110. To confirm specificity of the analysis, the amplification products of several samples were subjected to restriction enzyme digestion, or direct sequencing, or both. In 30 of the 41 cases analysed, ancient DNA was demonstrated by amplification by the presence of the human beta-actin or the amelogenin gene and nine of these cases were positive for M. tuberculosis DNA. The results were confirmed by restriction endonuclease digestion and sequencing. A positive result for M. tuberculosis DNA was seen in two of the three cases with typical morphological signs of tuberculosis and amplifiable DNA, in five of 13 non-specific, but probable cases (including two cases from c. 3000 BC), but also in two of 14 cases without pathological bone changes. These observations confirm that tuberculosis may be diagnosed unequivocally in skeletal material from ancient Egypt, even dating back to c. 3000 BC. As a positive molecular reaction was observed in most of the typical cases of skeletal tuberculosis, in about one-third of non-specific, but probable tuberculous osseous changes and, surprisingly, in about one-seventh of unremarkable samples, this suggests that infection with M. tuberculosis was relatively frequent in ancient Egypt.