Rare oral cancer under the microscope
MedWire News: Researchers have described a rare form of oral squamous cell carcinoma (OSCC), which has an unusual natural history and is difficult to diagnose.
Carcinoma cuniculatum (CC) poses a histopathologic challenge because of its low incidence and unique architecture, say Yan Sun (Nihon University, Matsudo, Chibo, Japan) and colleagues.
Sun's team searched the Nihon University School of Dentistry database for all cases of OSCC diagnosed between 1976 and 2010. Of 540 OSCC cases, just 15 (2.7%) met the World Health Organization criteria for CC; they included seven men and eight women with a mean age of 67 years (range 44-92 years).
The researchers retrieved clinical and follow-up information on all 15 CC cases and reanalyzed the samples to assess the tumor features in greater detail.
Writing in the Journal of Oral Pathology and Medicine, they report that seven of the patients had regularly consumed alcohol and/or tobacco. Three patients had leukoplakia, one had lichen planus, and one had both conditions. Two patients had additional tumors (liver and gastric cancer) while two patients showed signs of trauma.
Presenting symptoms included toothache (n=12), ulcer (n=8), induration (n=7), swelling (n=6), white patches (n=5), bleeding (n=4), and exudation (n=1). Symptoms had been present for 8.5 months, on average, at the point of diagnosis.
The most frequent sites for CC were the tongue (n=8) and mandible (n=6), and tumors ranged in size from 1.5 to 5.5 cm in diameter. Three cases metastasized to the lymph nodes, three cases recurred locally, and five cases had radiographic evidence of bone involvement.
On macroscopic examination, the tumors were grayish white-to-brown in color and were either exophytic with a granular or papillomatous surface, or endophytic, with an ulcerous or crater-like appearance.
Histopathologically, the major differences from other types of OSCC included unique, cuniculatum architecture and deep, branching crypts. The CC tumors were typically well-differentiated, lacked cytologic malignancy, and exhibited pearl-like keratin formations surrounded by well-differentiated squamous epithelium.
All tumors in this series were excised surgically, with microscopically negative margins. Of the three patients with recurrent CC, one recurred 12 years after initial surgery and subsequently died of an uncontrolled tumor with cachexia 6 months later; one received chemotherapy and local radiotherapy but developed lung metastasis and died 14 months later; and one case received chemotherapy but had progressive disease, but remains alive.
The mean follow-up duration after surgical excision was 45 months. Of 15 patients with data available, 2-and 5-year disease-free survival rates were 93.3% and 85.7%, respectively. One patient died of CC and a second patient died from other causes, giving a 5-year survival rate of 92.8%.
"Because of its well-differentiated status, the prognosis of CC is usually optimistic," Sun and co-authors conclude.
"However, recurrent cases in our study might have possessed invasive biological characters that were not well controlled by conventional treatment; in one case, a portion of the CC transformed into conventional squamous cell carcinoma. This might suggest that transformed CC rather than primary CC should be further emphasized."
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By Joanna Lyford