Perineural invasion in adenoid cystic carcinoma: Its causation/promotion by brain-derived neurotrophic factor.

Adenoid cystic carcinoma (ACC) is a common salivary gland neoplasm with a lengthy clinical course and often late local recurrences after surgical resection. This is accounted for histologically by its infiltrative capacity and distinct propensity for perineural invasion. The expression of biological markers may help explain the clinicopathologic course in ACCs. Brain-derived neurotrophic factor (BDNF) is a growth factor known to be involved in neurogenesis. The aim of this study is to elucidate the expression of BDNF in ACCs, which is currently unknown. Twenty-nine cases of primary ACCs of the head and neck were immunostained to analyze BDNF protein expression. Staining intensity was described as focal or diffuse and graded on a 3-tiered scale. The study group comprised 20 adult females (age 30 to 78) and 9 adult males (age 22 to 70). Sites of involvement included the parotid gland (6 cases), nasopharynx (5), maxilla (4), palate (3), trachea (3), submandibular gland (2), buccal mucosa (2), mandible (1), tongue (1), lacrimal gland (1), and temporal region (1). All tumors exhibited diffuse cytoplasmic staining; 11 cases were classified as 1+ intensity, 12 cases as 2+, and six cases as 3+. Based on the results presented here, BDNF is unformly expressed by ACC and may play a causative role in its predilection for perineural invasion. ACCs may display neurogenesis with high levels of BDNF expression in some tumors. Further studies are warranted to gain better understanding of this possible relationship.

Malignant melanoma of the oral mucosa in a 17-year-old adolescent girl.

Mucosal melanomas of the oral cavity are rarely seen in the United States. The hard palate is the most common intraoral site. This unusual case occurred in the oral cavity of a 17-year-old Asian girl, who presented to her dentist with complaints of pain and swelling in the upper jaw. The lesion was distal and palatal to the maxillary left second molar, which was vital. Interestingly, the clinical presentation was a hyperplastic, tender lesion that bled when probed. Histopathologically, the biopsy demonstrated a sheet of spindle-shaped cells arranged in nests and fascicles. The nuclei were vesicular, oval to spindle-shaped, and some contained nucleoli that were distinguishable but not prominent. No melanin pigment was observed in the lesion. Tumor cells strongly expressed S100 protein, gp100 (HMB-45), and microphthalmia transcription factor, and variably expressed MART1, but not cytokeratins, CD34, or muscle-specific actin. The histopathologic features and immunohistochemical findings are consistent with a diagnosis of malignant melanoma.

Odontogenic keratocysts arise from quiescent epithelial rests and are associated with deregulated hedgehog signaling in mice and humans.

Odontogenic keratocysts in humans are aggressive, noninflammatory jaw cysts that may harbor PTCH1 mutations, leading to constitutive activity of the embryonic Hedgehog (Hh) signaling pathway. We show here that epithelial expression of the Hh transcriptional effector Gli2 is sufficient for highly penetrant keratocyst development in transgenic mice. Mouse and human keratocysts expressed similar markers, leading to tooth misalignment, bone remodeling, and craniofacial abnormalities. We detected Hh target gene expression in epithelial cells lining keratocysts from both species, implicating deregulated Hh signaling in their development. Most mouse keratocysts arose from rests of Malassez--quiescent, residual embryonic epithelial cells that remain embedded in the periodontal ligament surrounding mature teeth. In Gli2-expressing mice, these rests were stimulated to proliferate, stratify, and form a differentiated squamous epithelium. The frequent development of keratocysts in Gli2-expressing mice supports the idea that GLI transcription factor activity mediates pathological responses to deregulated Hh signaling in humans. Moreover, Gli2-mediated reactivation of quiescent epithelial rests to form keratocysts indicates that these cells retain the capacity to function as progenitor cells on activation by an appropriate developmental signal.