Papillary thyroid carcinoma mistaken for malignant melanoma: pitfalls in diagnosis

Concomitant uveal melanoma and papillary thyroid carcinoma: a case report

Background

Melanoma develops in the cells that produce melanin; ocular melanoma accounts for 3–4% of all malignant melanomas. Thyroid tumors are the most common endocrine neoplasms, with more than 95% of cases arising from follicular cell origin. Previous studies have reported associations between malignant melanoma and a wide variety of malignancies.

Case presentation

We report a 54-year-old Iranian woman who was diagnosed with ocular melanoma based on a mushroom-shaped filling defect with homogeneous echo pattern arising from the anterior third of the temporal side of the globe detected on ocular sonography during routine ophthalmological examination. She underwent right globe enucleation and implant replacement. During tumor surveillance, fluorodeoxyglucose positron emission tomography/computed tomography scan showed low-grade metabolically active tumoral involvement in the anterolateral aspect of the right lobe of thyroid. The patient subsequently underwent thyroidectomy and submandibular lymphadenectomy. Pathologic report demonstrated micropapillary carcinoma (9 × 8 mm²), tall cell variant without lymphovascular or perineural invasion in the base of lymphocytic thyroiditis.

Conclusion

This case illustrates the importance of precise active surveillance in case of papillary carcinoma of thyroid or malignant melanoma to avoid missing other associated pathologies and emphasizes the simultaneous treatment of two tumors.

A comparative immunohistochemical study of MART-1 expression in Spitz nevi, ordinary melanocytic nevi, and malignant melanomas

BACKGROUND

The histopathologic differential diagnosis of Spitz nevus (SN) from malignant melanoma (MM) may be difficult.

OBJECTIVE

We attempted to elucidate the pattern of expression of a newly recognized melanocyte-specific melanosomal protein MART-1 in routinely processed specimens of SNs, MMs, and ordinary melanocytic nevi (MNs) and to see whether it can help to differentiate between them.

METHODS

Twenty SN, 22 MM, and 27 ordinary MN were immunostained with anti-MART-1 monoclonal antibody (clone A103).

RESULTS

All SNs, MNs, and MMs demonstrated cytoplasmic staining for MART-1 in some of their tumor cells, of which 17 of 20 (85%) and 24 of 27 (89%) of SN and MN, respectively, demonstrated positive stainings in more than half of their tumor cells, as compared with only 10 of 22 (45%) of the MM (P <.05). The majority of lesions in all 3 types of tumors showed a homogeneous mode of staining, although MM tended to show a more heterogeneous pattern. A consistent pattern of stratification of staining with progressive descent into the dermis was not demonstrated in these tumors.

CONCLUSION

MART-1 does not differentiate between SN, MM, and ordinary MN in a consistent pattern, but it may be used as a marker for these tumors.