ORLANDO – Matrilin-2 – a matrix protein found in peritumoral stroma – reliably distinguished invasive basal cell carcinoma from the often difficult-to-distinguish basaloid follicular hamartoma (BFH), in a study that evaluated the protein as a marker in this setting.
The protein marked 41 of 42 cancers and none of the hamartomas, Dr. Renato Goreshi reported at the annual meeting of the American College of Mohs Surgery. The one cancer it failed to identify was a superficial basal cell tumor – a finding that makes sense, since dermal fibroblasts appear to secrete matrilin-2 as a response to invasive skin tumors, said Dr. Goreshi of the Roger Williams Cancer Center, Providence, R.I.
Dr. Renato Goreshi
Mohs surgery typically employs hematoxylin and eosin staining to delineate tumor boundary. But, Dr. Goreshi said, that stain doesn’t always reliably differentiate adnexal tumors from basal cell carcinomas. “Basaloid follicular hamartoma can be particularly difficult to distinguish from basal cell carcinoma,” he said.
BFH typically presents as individual or linearly arranged, small skin-colored to brown papules or plaques, or as multiple lesions in a generalized distribution on the face, scalp, and occasionally, the trunk (Arch Pathol Lab Med. 2010 Aug;134[8]:1215-9). These are often stable for many years. The differential diagnosis includes basal cell carcinoma and trichoepithelioma.
BFH sometimes occurs near a BCC, although there are no data on how often this happens.
Dr. Goreshi cited a 2007 case report of a young woman that illustrates this problem. The patient presented with a basal cell carcinoma on the side of her nose. The adjacent BFH was unrecognized, however. She underwent a multiple-stage Mohs that was unnecessarily extended because tumor margins included sections of the BFH.
“The lesion was interpreted as malignancy by both the Mohs surgeon and the dermatopathologist, but was later determined to have been a hamartoma. This highlights the importance of finding an effective marker,” Dr. Goreshi said.
He and his fellowship director, Dr. Satori Iwamoto, chief of Mohs micrographic surgery at Roger Williams, looked for a reliable way to differentiate these tumors, capitalizing on the invasive nature of BCC. The peritumoral stroma plays a role in tumor growth and invasion. It involves fibroblasts, inflammatory and endothelial cells, and extracellular matrix proteins. Matrilin-2, which is involved in the formation of filamentous networks, was a promising candidate and the initial investigations looked good, said Dr. Goreshi said.
Their confirmatory study comprised 42 BCC and seven BFH sections that were obtained during Mohs surgery. All were stained for matrilin-2 and scored for location and intensity of staining by two reviewers. The investigators also conducted flow cytometry to determine the source of the protein.
The BCC set consisted of 11 morpheaform/infiltrative BCCs, 25 nodular BCCs, and 6 superficial BCCs. With the exception of one superficial lesion, all of these stained positive for matrilin-2 in the peritumoral stroma. None of the BFH sections stained positive for the protein, however. Flow cytometry determined that the protein was coming from dermal fibroblasts in the stroma.
This is actually a key point, Dr. Goreshi noted. “Matrilin-2 is not acting as a conventional tumor marker would, but as a marker of invasion.”
This was again played out in the variation of staining intensity in the tumor subtypes. It was most intense around the infiltrative subtypes. There was also adnexal staining, but it was significantly less than what was seen in the peritumoral stroma. There was virtually no staining in or around the hamartoma.
Staining was not as intense around the superficial BCC subtypes. In fact, it was not significantly different from what was seen in the adnexal structures. Again, however, there was no staining in or around the hamartoma.
“Now we are looking at the staining patterns of other lesions, including melanoma and squamous cell carcinoma, and trying to figure out why the dermal fibroblasts are secreting matrilin-2,” Dr. Goreshi said.
The study was the winner of the 2016 Theodore Tromovitch Award, presented for original research conducted by a fellow-in-training during his or her year of training.
Neither Dr. Goreshi nor Dr. Iwamoto had any relevant financial disclosures.