basaloid neoplasm

basaloid neoplasm

A term of art used in cytopathology for a family of cytologically (by fine needle aspiration, FNA) similar tumours which cover the entire spectrum of biologic behaviour, from benign and low-grade malignancies to the aggressive solid variant of adenoid cystic carcinoma. In contrast to the other lesions assessed by FNA, in which differentiating benign from malignant lesions is relatively straightforward, precise cytologic diagnosis is not possible with many FNAs that show basaloid cells only.

DiffDx
• Chronic sialadenitis;
• Cellular pleomorphic adenoma;
• Basal cell adenoma;
• Basal cell adenocarcinoma;
• Metastatic basal cell carcinoma (extremely rare);
• Metastatic basaloid squamous cell carcinoma
• Adenoid cystic carcinoma (solid variant);
• Small cell carcinoma.
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TABLE 1 Distribution and Frequency of Parotid Tumors by Pathology and Patient Sex Type of Tumor Male Female Benign Pleomorphic adenoma 2 16 Warthin's tumor 6 2 Inflammatory 1 5 Monomorphic adenoma 3 Lipoma 1 Subtotal 13 23 Malignant tumors Squamous cell carcinoma 5 1 Adenocarcinoma 3 2 Lymphoma 1 1 Merkle cell carcinoma 1 Basaloid neoplasm 1 Subtotal 11 4 Total 24 27 Type of Tumor Total Benign Pleomorphic adenoma 18 Warthin's tumor 8 Inflammatory 6 Monomorphic adenoma 3 Lipoma 1 Subtotal 36 Malignant tumors Squamous cell carcinoma 6 Adenocarcinoma 5 Lymphoma 2 Merkle cell carcinoma 1 Basaloid neoplasm 1 Subtotal 15 Total 51 TABLE 2 Pathology as Function of Sex Sex Nonmalignant Malignant Total Female 23 4 27 Male 13 11 24 Total 36 15 51 DF Value Probability Chi-square 1 5.
One of the challenging issues within the basaloid neoplasm category is the diagnosis of AdCC on cytology aspirate.
Other markers that could be useful in the setting of a basaloid neoplasm in which AdCC is in the differential diagnosis have been investigated on resection specimens, rather than cytologic material.
Primary parotid tumors that can show a pleomorphic basaloid neoplasm on aspiration include lymphoepithelial carcinoma, salivary gland carcinomas with high-grade transformations, or occasional low-grade malignancies, such as EMCA.
Basaloid neoplasms were further stratified based on stromal characteristics in monomorphic smears with an additional category of pleomorphic basaloid neoplasms.
CD117 is a sensitive immunohistochemical marker for AdCC, but it can stain nearly 20% of benign PAs, the most common neoplasm of the salivary gland and the most frequent differential diagnosis for a basaloid neoplasm.
One of the main challenges is the basaloid neoplasm pattern, which is generally characterized by an FNA aspirate that demonstrates a cellular population of small cells aggregated in loosely cohesive groups with scant to absent background mesenchymal material (see Figures 2, A and B; 3, A and B).
Other tumors from the basaloid neoplasm category, such as basal cell adenoma and basal cell carcinoma, were not available to use.
However, if the stromal component is scanty or missing, and smears are highly cellular, the distinction from basaloid neoplasms and myoepithelial adenoma can be difficult or even impossible.
The solid variant of ACC is therefore much more difficult to diagnose on FNA than the classic type, and it is usually suggested as part of a differential diagnosis, typically in the setting of basaloid neoplasms.
Another limitation of both the study of Hudson and Collins, (1) as well as our study, (2) is that other less common basaloid neoplasms that enter into the differential diagnosis of AdCC and PA were not evaluated.
This feature, along with accompanying areas of cribriform or tubular growth, can aid in differentiation from other basaloid neoplasms.