Case of Metastatic Malignant Melanoma Simulating Granuloma Annulare

Haley Danielle Heibel,Etan Marks,Clay J Cockerell,Parneet Dhaliwal

doi:10.25251/skin.5.3.12

Abstract

Malignant melanoma and particularly metastatic melanoma represent a diagnostic challenge due to the wide variety of histologic patterns, resemblance to benign entities, and extensive range of clinical presentations. A high index of suspicion for melanoma is important for accurate diagnosis, especially when there is a previous history of malignancy. Here, we present a patient with a history of melanoma and locally metastatic melanoma, who subsequently developed a nodule on his right forearm near the site of his previous melanoma excision. Histologically, the melanoma appeared as granuloma annulare (GA) with benign cytologic features, but was identified as metastatic melanoma using SOX-10 immunohistochemical staining. Other malignancies, including lymphomas, leukemias, sarcomas, and cutaneous metastases of internal malignancies, have mimicked GA and interstitial granulomatous processes. Therefore, further immunohistochemical staining should be performed to assess for metastatic disease in the setting of a histological pattern that resembles a benign granulomatous process in a patient with a history of malignancy, including malignant melanoma.

Highlights

Malignant melanoma is a complex malignancy that can present with a wide range of histological patterns, including mimicking other malignant tumors and benign entities, such as interstitial granulomatous processes.[1,2] metastatic melanoma has a wide variety of clinical presentations that may not be visible to the clinician and may not seem suspicious for melanoma.[1]
Granulomatous reactions associated with melanoma, cutaneous granulomatous reactions following the initiation of treatment for metastatic melanoma, and metastatic melanoma mimicking an interstitial granulomatous reaction have been reported.[1,4,5,6,7,8]
Metastatic melanoma can present with a wide variety of clinical presentations.[1]

Summary

INTRODUCTION

Malignant melanoma is a complex malignancy that can present with a wide range of histological patterns, including mimicking other malignant tumors and benign entities, such as interstitial granulomatous processes.[1,2] metastatic melanoma has a wide variety of clinical presentations that may not be visible to the clinician and may not seem suspicious for melanoma.[1]. An 89-year-old male with a history of melanoma presented with a flesh-colored nodule on the right dorsal forearm adjacent to the site of the previous melanoma excision (Figure 1) His primary melanoma had been diagnosed 14 years previously on his right forearm with an initial depth of 1.4 mm (pathologic stage: pT2a). He had 3 locally metastatic melanomas near the surgical excision site of the original melanoma occurring 11, 5, and 1 year(s) prior to presentation. When the third locally metastatic melanoma developed on his right forearm, he again underwent excision of this lesion At this time, a PET/CT scan demonstrated an enlarged 1.6 cm right sided pelvic lymph node, CT-guided FNA of the right pelvic lymph node was nonspecific. After its initial identification, but no other evidence of metastases or disease progression has been identified

DISCUSSION

CONCLUSION