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Case Presentation - Summer, 2014

Ameloblastoma

Written by: Lindsay Shearer, student, Cleveland Clinic School of Cytotechnology, Cleveland, Ohio


Patient Age: Male, age 62

Patient History: History of maxillectomy and radiation. Patient now presents with right lower eyelid swelling for the past 3 months. CT scan showed a 3.7cm mass in the left lower lobe of the lung along with 2 cm masses in both upper poles of the lungs.

Specimen type: FNA of the Lung, ThinPrep® Non-Gyn cytology

Cytologic Diagnosis: Suspicious for an Ameloblastoma neoplasm

Biopsy Diagnosis: Concurrent biopsy of the left lung - Neoplasm consistent with Metastatic Ameloblastoma

Case provided by: Susquehanna Health-Williamsport Hospital, Williamsport, PA

Ameloblastoma

Etiology:
Ameloblastomas are rare intraosseous odontogenic neoplasms that account for a small proportion of jaw tumors. They are thought to arise from the epithelial cells of the enamel-forming organ within dentigerous cysts. The etiology is uncertain but irritation, infection, trauma and nutritional deficiency have been proposed as contributory agents for carcinogenesis. The majority of tumors occur in the mandible but can also develop in the maxilla. Most ameloblastomas are aggressively destructive to neighboring tissues but rarely metastasize. Therefore, they are sometimes regarded as benign or borderline tumors, or as locally malignant. When metastases do occur the most frequent site is the lung.

Clinical Features:
Ameloblastoma tumors are slow growing and often painless. They can either be solid growing, cystic or ulcerated and are sometimes necrotic. Swelling is the predominate symptom and can occur in the cheek, gums or hard palate. In maxillary tumors, other symptoms include pain, nasal obstruction and nose bleeds. Metastatic ameloblastoma usually presents as multiple lung nodules.

Treatment and Prognosis:
Treatment options include enucleation with curettage, marginal resection and radical resection. Recurrence is common, especially with more conservative treatment methods and with certain histologic variants. Since metastatic potential is low, conservative treatments may be desirable for patients with early disease and without aggressive histologic types. Multiple recurrences can eventually be treated with resection. Undetected recurrence in the maxilla is more common and dangerous than that in the mandible, so conservative treatments may not be wise in such cases. The five year survival rate is high, upwards of 80%. Metastatic disease responds poorly to both chemotherapy and radiation, so it is most effectively treated with lung resection.

Cytology:
Most ameloblastoma tumors are diagnosed histologically, but sometimes cytologically, especially in cases of metastasis. Fine needle aspirate (FNA) is the cytological sampling method of choice. An FNA will show sheets or tight clusters of basaloid cells with scant, bland cytoplasm, elongated nuclei with finely distributed chromatin and inconspicuous nucleoli. Fibroblastic stroma may also be present and will consist of palisading stromal cells with stellate reticulum in the center. Squamous cells, ranging from immature metaplastic cells to keratinized pearls, can also be present. Nuclear atypia is not a feature of this tumor.

Differential Diagnosis:
Ameloblastic fibroma is the main tumor that may be mistaken for ameloblastoma. It is a benign primary intraosseous tumor, often in an area surrounding an unerupted tooth in adolescents. It has a nearly identical cytological picture and may not be distinguishable. The only possible cytologically observable difference is that ameloblastic fibromas have a larger stromal component than ameloblastomas. Odontogenic cysts may also be mistaken for ameloblastoma based on imaging, but should not be confused cytologically. Basaloid squamous carcinoma originating in the head and neck region is also in the differential. These tumors show similar basaloid features but lack the stromal component that is essential for the diagnosis of ameloblastoma.

References:
  1. Ciment LM, Ciment AJ. Malignant ameloblastoma metastatic to the lungs 29 Years after primary resection. Chest Journal 2002;121(4):1359-1361.
  2. DeMay RM. Soft Tissue, Bone, and Skin. In: The Art & Science of Cytopathology. 2nd ed. Hong Kong: ASCP Press; 2012:704.
  3. Hong J, et. Al. Long-term follow up on recurrence of 305 ameloblastoma cases. International Journal of Oral and Maxillofacial Surgery. 2007;36(4): 283-288.
  4. Kim SG, Jang HS. Ameloblastoma: A clinical, radiographic, and histopathological analysis of 71 cases. Oral Surgery Oral Medicine Oral Pathology Oral Radiology and Endodontology. 2001;91(6):649-653.
  5. Raher GR, et al. Fine needle aspiration cytology of ameloblastoma. JK Science. 2013; 15(2):98-100.
  6. Sehdev MK, et al. Ameloblastoma of maxilla and mandible. Cancer. 1974;33(2):324-333.