Biopsy from a young adult with an orbital mass and pain
For those of you sitting exams (whether ophthalmologists or histopathologists), this is a classic pattern to recognise. It shows cribriform (“sieve-like”) architecture, sometimes compared to Swiss cheese for obvious reasons. There are nests of basaloid tumour cells containing punched-out cystic spaces filled with mucin. There is also a little mucin between the nests and the surrounding stroma (similar to the “cracking artefact” of nodular basal cell carcinoma).
In the annotated image, I’ve outlined mucin pools in blue, and marked the mucin in the nest/stroma interface in yellow.
Cribriform architecture is a strong pointer towards a diagnosis of adenoid cystic carcinoma although it shouldn’t be taken in isolation. As with all diagnostic histopathology, you need to take all the microscopic features into account as well as clinical history and presentation. In the case of orbital masses, radiology should also be considered. This tumour originated from the lacrimal gland although there is extensive infiltration of the orbital soft tissue.
The tumour cells are fairly uniform in appearance, but beware: the tumour is malignant.
This image shows crush artefact as well as another classic feature of adenoid cystic carcinoma. Groups of tumour cells both surround the nerve and invade it.
In the annotated image, I’ve outlined the nerve in blue. The area of crush artefact is hatched in yellow. Some types of tumour cells (for example, small cell carcinoma of the lung) are fragile and prone to crushing, which can be a useful sign. In this specimen, the tissue just happens to be crushed.
Adenoid cystic carcinoma frequently shows microscopic peri- or intraneural infiltration. This explains why pain is so frequently a presenting feature.
The architecture of adenoid cystic carcinoma may be cribriform (commonest), tubular or solid (rarest), and often a combination. This is an example of tubular architecture. In contrast to the cribriform pattern, the tumour nests are smaller and show a (roughly) single central lumen.
In the annotated image, I’ve outlined a few lumina in blue. The elongated ones may be genuinely that shape in cross-section, or perhaps the tubule is obliquely orientated relative to the section.
Solid nests are associated with a poorer prognosis than the other patterns. This is a low power image of a case that had classic cribriform areas elsewhere. This field shows mainly solid nests, but there are also areas of comedo necrosis, which I think is an unusual feature. Even the solid nests have tiny cystic spaces in this case, but they’re not a major feature.
In the annotated image, I’ve outlined the areas of comedo necrosis (large areas of debris from dead cells) in blue.
Admission: While I recognise comedo necrosis when I see it, I’m struggling to define it succinctly. Do any readers want to offer suggestions in the comments?
Adenoid cystic carcinoma is rare in the lacrimal gland. Our department sees maybe four or five cases in an average year. It’s more common in the salivary glands, and it also occurs (rarely) at other body sites such as in the breast and skin. Much of the literature focusses on salivary gland tumours, with cautious extrapolation to lacrimal gland.
Here are some open access references, which I hope will be helpful to both ophthalmologists and histopathologists
The Radiological Spectrum of Orbital Pathologies that Involve the Lacrimal Gland and the Lacrimal Fossa by Jung et al. As the name suggests, this article is an overview of entities occurring in the lacrimal gland and lacrimal fossa.
Note: “Lacrimal fossa” is a slightly ambiguous anatomical term, since it is sometimes used to refer to the lacrimal sac fossa (which lies inferomedially within the bony orbit) as well as the lacrimal gland fossa (superotemporally within the bony orbit). They are separate locations! In this article, the authors refer purely to the fossa where the lacrimal gland lies.
Adenoid Cystic Carcinoma by Jaso and Malhotra is a succinct introduction to the histopathology of adenoid cystic carcinoma
Epithelial tumours of the lacrimal gland: a clinical, histopathological, surgical and oncological survey by von Holstein et al. I find this article provides a very useful and comprehensive review.
For those with a more molecular biology bent (which doesn’t include me!):
Adenoid cystic carcinomas of the salivary gland, lacrimal gland, and breast are morphologically and genetically similar but have distinct microRNA expression profiles by Andreasen et al. I’ve mentioned above that there’s a tendency to extrapolate salivary gland findings to lacrimal gland, so it’s interesting to see some differences being teased out.
Mutational Landscape of Lacrimal Gland Carcinomas and Implications for Treatment by Bell et al is a more general study on lacrimal gland carcinomas.