|Year : 2016 | Volume
| Issue : 1 | Page : 48-51
Squamous cells and keratin pearls in fine-needle aspiration and frozen section: A pitfall in the diagnosis of ameloblastic carcinoma
Ankita Baldwa, Rashmi Krishnappa, Aarathi Rau, Usha Muniyappa, G Girish
Department of Pathology and Surgical Oncology, M.S. Ramaiah Medical College and Teaching Hospital, Bengaluru, Karnataka, India
|Date of Web Publication||11-Aug-2016|
50/3, 1st Main, 1st Cross, Nanjappa Layout, Vidyaranyapura, Bengaluru - 560 097, Karnataka
Source of Support: None, Conflict of Interest: None
Intraosseous involvement of jaw bones are commonly seen with squamous cell carcinoma (SCC) of the oral cavity. Ameloblastic carcinoma (AC) is a rare malignant odontogenic neoplasm that tends to occur in mandible with or without intraosseous involvement. We present one such rare case of, 60-year-old female with gray white growth in the left lower buccal cavity with enlarged lymph nodes. The computed tomography scan showed a mass from the left submandibular salivary gland and fine-needle aspiration was suggestive of malignant salivary gland tumor. The patient was posted for frozen section and mandibulectomy. Frozen section showed squamous cells with keratin pearl formation suggestive of metastatic SCC. The routine histopathology proved it as AC with keratin pearl formation. With this case, we would like to highlight the pitfalls, difficulties, and importance in the diagnosis of AC.
Keywords: Ameloblastic carcinoma; fine-needle aspiration; frozen section; keratin pearls; squamous cells
|How to cite this article:|
Baldwa A, Krishnappa R, Rau A, Muniyappa U, Girish G. Squamous cells and keratin pearls in fine-needle aspiration and frozen section: A pitfall in the diagnosis of ameloblastic carcinoma. Indian J Multidiscip Dent 2016;6:48-51
|How to cite this URL:|
Baldwa A, Krishnappa R, Rau A, Muniyappa U, Girish G. Squamous cells and keratin pearls in fine-needle aspiration and frozen section: A pitfall in the diagnosis of ameloblastic carcinoma. Indian J Multidiscip Dent [serial online] 2016 [cited 2020 Aug 8];6:48-51. Available from: http://www.ijmdent.com/text.asp?2016/6/1/48/188234
| Introduction|| |
The jawbones can be involved by a multitude of neoplastic conditions and giving a precise diagnosis often can be challenging. Malignant tumors of the mandible and maxilla can be categorized as: (1) Primary (2) invasion from adjacent tumors and (3) metastatic tumors.  Ameloblastoma is tumors of odontogenic epithelium constitutes about 1-3% of primary jaw tumors and cysts  and its malignant counterpart ameloblastic carcinomas (ACs) are exceptionally rare showing cytological features of malignancy with or without metastasis. It was recognized as a separate entity by the World Health Organization in 2005.  Two forms are recognized: A primary de novo type (AC was classified into primary type [ACPt]) and a secondary (dedifferentiated) (ACSt) type arising in a preexisting benign ameloblastoma. They are further classified as either intraosseous or peripheral in location.  We report one such case of AC and the diagnostic difficulties for the same.
| Case Report|| |
A 60-year-old female presented with a swelling on the lower left side of the jaw of 6 months duration. The swelling gradually increased in size and was associated with pain. She had been chewing betel nut for 40 years. On local examination, the swelling in the submandibular region was hard, nontender and fixed; measuring 6 cm × 6 cm. Intraorally, there was an ulcerated area with normal mouth opening and teeth. The left submandibular lymph nodes were enlarged. Computed tomography (CT) scan neck revealed a mass measuring 3.5 cm × 4.5 cm × 4 cm arising from the anterior aspect of the left submandibular salivary gland with solid and cystic areas. There were enlarged lymph nodes in the submental and the submandibular region. There was mandibular bone erosion adjacent to the mass. CT scan was interpreted as suggestive of malignant salivary gland tumor with bone erosion and metastasis to lymph nodes [Figure 1]. Fine-needle aspiration cytology (FNA) done elsewhere, suggested mucoepidermoid carcinoma of salivary gland origin. Hence, a working diagnosis of left submandibular salivary gland carcinoma with metastatic lymph nodes was made.
|Figure 1: Computed tomography scan showing mass arising from left submandibular gland which has solid and cystic areas. Inlet showing mandibular bone erosion adjacent to the mass|
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The patient was posted for left posterior segmental mandibulectomy and modified radical neck dissection. Intraoperatively, the mass was fixed to the mandible, and the overlying skin was pinchable. Level 1a lymph node was sent for the frozen section which showed lymph node almost completely replaced by tumor composed of large polygonal squamous cells and keratin pearl formation. It was reported as positive for malignancy suggestive of metastatic squamous cell carcinoma (SCC) [Figure 2]. The left-sided segmental mandibulectomy grossly showed a gray white tumor with cystic and solid areas. The tumor appeared infiltrating the underlying bone and adjacent soft tissue [Figure 3]. Formalin-fixed and paraffin-embedded sections stained by hematoxylin and eosin stained slides showed infiltrating tumor composed of islands of tumor cells with peripheral palisading tall columnar cells exhibiting reverse polarity with their nuclei placed away from basement membrane, nuclei were vesicular with prominent nucleoli and irregular nuclear contour. Within these were stellate cells with moderate pleomorphism. Few cells with keratinization, intercellular bridges, and keratin pearl formation were seen [Figure 4]. Perineural and lymphatic invasion were present. Underlying bone and adjacent soft tissue were involved by the tumor. Of 29 lymph nodes, 12 were involved by metastasis. The salivary gland was free from tumor. Hence, the final diagnosis of AC - intraosseous type was made after extensive sampling.
|Figure 2: Microphotograph showing squamous cells with keratin pearls in the lymph node section sent for frozen section (H and E, ×400)|
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|Figure 3: Cut section of segmental mandibulectomy specimen showing grey white tumor, solid and cystic nature of tumor|
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|Figure 4: Microphotograph showing single tumor island with peripheral palisading cells, central stellate reticulum cells and adjacent stroma (H and E, ×100). Inlet showing pleomorphic tumor cells with high nucleo-cytoplasmic ratio, prominent nucleoli and a mitotic figure (H and E, ×400)|
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| Discussion|| |
In 2003, Avon et al.  introduced the term AC to describe ameloblastoma in which there had been histological evidence of malignant transformation. AC occurs in a wide range of age groups with the mean age of 30 years and no apparent sex predilection. The most commonly involved area is the posterior portion of the mandible as in the present case. Swelling associated with pain, rapid growth, trismus, and dysphonia are common symptoms.  In a review of 31 cases by Casaroto et al.  75% were ACSt and 25% were ACPt. Although we could not ascertain whether AC in our patient developed de novo or from a preexisting ameloblastoma, we believe the former might be the most likely due to the absence of any history of previously operated tumor, short duration of the lesion and there were no benign ameloblastoma-like areas on histopathological examination.
The hallmark of AC is extensive tooth root absorption. CT helps in evaluating the extent of the lesion, cortical perforation, and adjacent soft-tissue involvement. The presence of more aggressive features such as large solid components, papillary projections, extraosseous extension, and invasion is suggestive of malignancy.  Extensive root resorption was not seen in a case report of AC by Casaroto et al.  even in our case, there was no tooth root resorption. The CT scan in our case showed a mass arising from the left submandibular salivary gland with mandibular bony erosion adjacent to the mass. In retrospect, this was mandibular expansion which had pushed the salivary gland.
Nai and Grosso  reported a case of AC, which was diagnosed on FNA revealed highly cellular smears with cells in a palisade arrangement. A dual population of basaloid, stellate-shaped cells and atypical cells with mitotic figures are seen consistently with AC. These findings were not seen in our FNA, instead the malignant squamous cells were sampled hence a diagnosis of mucoepidermoid carcinoma of the submandibular salivary gland was made in view of CT findings.
The lymph node which was sent for frozen section showed squamous cells and keratin pearls and was reported as positive for malignancy suggestive of metastatic SCC. Retrospectively, stellate cells were identified in the frozen section [Figure 5]. Typical features of AC as seen by Kumaran et al.  are tumor islands appearing odontogenic in origin with each showing peripheral columnar cells with central stellate reticulum exhibiting feature of ameloblastoma, but with atypical features such as bizarre mitosis, altered nuclear-cytoplasmic ratio, hyperchromasia, and pleomorphism. Central stellate reticulum appears to be condensed and hypercellular. Similar histopathology findings were seen in our case also. Very few cases of AC with prominent squamous differentiation and keratinization have been reported previously. ,,
|Figure 5: Retrospective analysis of lymph node sent for frozen section showing stellate cells (H and E, ×400)|
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In this case, squamous differentiation and keratin pearls were seen which misled towards the diagnosis of mucoepidermoid carcinoma on FNA and metastatic SCC on frozen section. The histopathological differential diagnosis of AC includes primary intraosseous SCC, mucoepidermoid carcinoma, SCC arising in odontogenic cysts and tumors metastasizing to the jaws. 
| Conclusion|| |
Although AC is a rare tumor, it should be kept in mind while evaluating the tumors of jaw bones, these tumors can be masked by extensive squamous differentiation and keratin pearl formation.
We would like to acknowledge Head of the Department of Pathology Dr. Vijaya Mysorekar for her support.
Financial support and sponsorship
Conflicts of interest
There are no conflicts of interest.
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[Figure 1], [Figure 2], [Figure 3], [Figure 4], [Figure 5]