Oral and Maxillofacial Pathology
Transformation of a benign oral pigmentation to primary oral melanoma

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Objective

The objective is to report the serendipitous 7-year follow-up and transformation of a melanotic palatal lesion, which was initially diagnosed histologically as a benign oral melanotic macule, into primary oral melanoma and to provide long-term follow-up of a case of oral malignant melanoma.

Study design

Nine formalin-fixed paraffin-embedded tissue blocks from several different facilities and microscopic slides of the patient's lesions were reviewed to study the transformation of a benign, oral, pigmented lesion into melanoma.

Results

Review of blocks and slides of the patient's lesions suggest that the onset of melanocytic hyperplasia (increased clear cell activity) heralded the transformation of the melanotic macule into melanoma. The histology of the first biopsies was totally benign, but retrospectively, the clinical appearance was not typical and was somewhat worrisome because of the size of the lesion and feathering of the pigmentation at the periphery. This clinical presentation, however, was unknown to the pathologists.

Conclusions

This study documents a case of primary oral melanoma arising from an apparent oral melanotic macule and suggests that even histologically benign–appearing oral melanotic lesions should perhaps be viewed with caution if increased numbers of melanoctyes (melanocytic hyperplasia or clear cell activity) are present. Careful correlation of clinical appearance and histology is necessary to arrive at an appropriate diagnosis and prognosis for oral pigmented lesions.

Section snippets

Case report

Several medical and dental practitioners provided care for a 38-year-old white woman over a 13-year period, with 7 incisional biopsies, 3 excisional biopsies, and 2 surgical excisions resulting in 14 initial or consultative histopathological diagnoses. The histological diagnoses were made at 5 pathology laboratories (general, oral, and dermatologic) and 3 local hospitals.

Nine formalin-fixed, paraffin-embedded tissue blocks were cut and reviewed by 2 oral and maxillofacial pathologists (D.R.W.

Discussion

An English language literature search failed to discover a previously reported case of a histologically documented oral melanotic macule that transformed into primary oral melanoma. However, Taylor and Lewis15 in 1990 reported a case of anterior mandibular gingival melanoma in a 27-year-old white man. The melanoma was histologically documented 5 years previously with a diagnosis of “benign gingival melanosis.” The benign pigmented lesion was described as possessing anastomosing and elongated

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